Write the numbers one below another in question and make 10 ques of 3 digit addition with 2 numbers

Broken windows are covered. Floorboards are patched and doors screwed back on. The road that was ruined by German tanks is shovelled and raked smooth. Boot-shaped bruises turn yellow then fade and disappear. Flowers grow and spread across the ugly German footprints stomped into garden beds. The village looks pretty once more. School stops for the summer and everyone is put to work on the kolkhoz, the village farm. Women and big boys begin harvesting the barley crops in the outer fields. The biggest girls milk the cows, morning and night, and keep the barns clean. Old Nikolay mends ploughs, horse harnesses, pitchforks and scythes in his workshop. Anna Pushinka teaches Yelena and her friends how to get the honey from the beehives that are scattered through the orchards. I am in charge of collecting eggs. My friends Olga and Nina help. Olga and Nina are five, a year younger than me. They are twins and look exactly alike, except Nina’s nose is a little bit crooked from when she fell out of bed and squashed it sideways on the floor. The hens, ducks and geese wander free in the summer, so collecting eggs is like a treasure hunt and takes hours. Catching the hens for their daily hugs takes even longer, but I think it’s important because hugs make everyone happy and happy hens lay bigger eggs. Olga says I’m the best hen-hugger in all of Russia. Nina says I’ll be the best cow-hugger, too, when my arms grow longer. But good hugs have nothing to do with the size of your arms. It’s all to do with the size of your heart. When we are done with the hens, Olga, Nina and I can spend the rest of the day doing whatever we like. We climb the apricot trees, chase squirrels, lie in the meadow marvelling at how hot Ushanka’s black fur becomes in the sunshine, make daisy chains and race little boats of bark in the stream. I teach Olga and Nina the alphabet and we use charcoal to write our letters and our names all over the village – on doors and walls and the freshly cut ends of firewood. In between, I practise my knots. In case the German princemonsters return. I slip into Old Nikolay’s workshop and tie knots in the harnesses hanging on the walls. I wander into gardens where the washing is hung out to dry and tie knots in the laces on pants and smocks. I creep up behind Anna Pushinka and tie knots in her apron strings. I find baling twine in the hay shed and tie my own ankles together. I do such a good job of these last knots that I can’t get them undone. I have to jump all the way to Olga and Nina’s house and ask them to cut me free with their mama’s knife. At the end of each day, Ushanka and I run out into the distant barley fields to meet Mama. This is my favourite part of the day, because Mama always shouts, ‘Little Rabbit!’ and smothers my head with kisses. And as we walk home, we sing. Everyone – women, big boys and me. I love to sing. Almost as much as I love to be kissed by Mama. Sometimes one of the boys, Mikhail, has his balalaika with him. He takes the instrument out from beneath the sheaves of barley piled high on the wagon and plays music. We sing about forests and orchards and people who find their true love. As we walk home, arm in arm, my heart fills with happiness and my belly swells with pride that I am allowed to sing along with the big boys. And I can almost forget about the German prince-monsters and their lies about Russia and their big ugly boots. Almost. But today, when Mikhail reaches for his balalaika, I see other things hiding beneath the barley sheaves. Three of the mamas rush forward and cover them up, but it’s too late. I know they are there. I’ve already seen them. Rifles. Lots of rifles. Mikhail hugs his balalaika to his chest and blushes. ‘So play!’ cries Mama, her voice oddly loud and high. ‘Let’s play Sasha’s favourite song, “The Little Birch Tree”.’ So Mikhail plays and everyone sings about the lovely birch tree with its curly leaves and the branches that will be turned into silver flutes. They sing too quickly, too loudly, and as they sing and walk, they cast nervous sideways glances at me. ‘It’s alright,’ I say, when the song comes to an end. ‘I didn’t see the rifles.’ Mama nods and smiles, and I know it was the right thing to say. But I did see the rifles. And I think about Yelena wanting to get lots of guns and dynamite for the Partisans so they can shoot the Germans and blow them into thousands of tiny pieces, and Mama looking as though she agreed, and I know this is what the mamas and the big boys are doing. As well as harvesting, they are helping the Partisans. Three days later, I wake before dawn and I am all alone. Yelena is always here beside me when I wake. But not this morning. I climb down from our bed above the stove. Mama is filling a cloth sack with bread. She ties it closed with a piece of string and hands it to Yelena. ‘Stay out of sight,’ says Mama. ‘And don’t return until after dark.’ ‘Where’s she going?’ I ask. ‘Nowhere,’ snaps Mama. ‘Then why does she need all that bread?’ I ask. ‘There’s nothing left for us.’ Mama baked four loaves last night and she has stuffed them all into the sack. Yelena opens her mouth, but before she can speak, Mama shoves her out the door and sends her on the way to nowhere. Mama turns and stares at me, her blue, blue cornflower eyes wide with worry. ‘I know,’ I say, flopping down on the bench. ‘I didn’t see any bread.’ Mama sits beside me and takes my hand. ‘And . . .?’ she prods, obviously waiting for more. I puzzle for a while, then say, ‘And I don’t have a sister called Yelena.’ Mama laughs, softly and with a little bit of sadness around the edges. ‘Sweet Little Rabbit! You do have a sister called Yelena.’ ‘I do?’ I ask, now confused. ‘I haven’t seen the rifles or the bread, but I have seen Yelena?’ ‘Yes.’ Mama smiles and the magic makes me smile, too. And I am glad that Yelena is real because I love her very much. ‘Yelena is real,’ Mama explains, ‘but she does not carry sacks of bread into the forest for the Partisans.’ ‘Of course not!’ I shout, slapping my forehead. ‘Because there is no bread!’ Mama laughs loudly now, with not a hint of sadness. She hugs me, pressing me against her warm, loving heart, covering my head with kisses. ‘Clever Little Rabbit,’ she murmurs, and then, in barely a whisper, ‘Your papa would be so proud.’ When I wake the next morning, Yelena is sleeping beside me, her mouth open, her braided hair unravelling. Mama is serving kasha to a strange woman seated at our table. I crawl down from above the stove and slide along the bench beside her. I stare at her pants, her tunic, the rope she is using as a belt and her big boots. She’s dressed like a man! And there’s a rifle leaning against the wall near the door. ‘Hello,’ I say. ‘I’m Sasha.’ The woman doesn’t reply. She just shovels down her kasha. I line my four wooden bears along the table in front of her bowl and say, ‘These are my bears: Big Bear, Medium Bear, Little Bear and Even Littler Bear.’ ‘Hello, Sasha. Hello, bears.’ She smiles but she doesn’t tell me her name. ‘Why are you dressed like a man?’ I ask, tugging at the sleeve of her tunic. ‘Because men’s clothes make it easier to run and climb and crawl and shoot,’ she says. ‘You’re a Partisan!’ I gasp. ‘But she’s not real,’ says Mama, placing a bowl of kasha before me. ‘Is the kasha real?’ I ask. Mama laughs. ‘Yes, Little Rabbit.’ I’m glad the food is real, because I’m hungry. But I’m disappointed that the woman is not real. I was going to ask if I could use her rope-belt to tie her ankles together. For practice. But if she’s not real, then the rope and her ankles aren’t either. The woman finishes her kasha, hangs her rifle over her shoulder, kisses Mama on the cheek then slips out the door. I run to the window to watch her leave, but by the time I get there, she’s gone. Vanished. ‘Because she’s not real,’ I whisper. A week later, Mama and I are working in the garden. We sing as we weed between the flowers and pluck caterpillars from the vegetables. Anna Pushinka is picking strawberries in her garden and wanders over. ‘Taste these,’ she says, holding out the basket. Mama reaches in and takes out a fat strawberry and a tiny piece of folded paper. The strawberry goes into her mouth, the paper into her pocket. ‘What’s on the paper?’ I ask. ‘Paper?’ Anna Pushinka replies with a wave of her hand. ‘Goodness, Sasha! Who has money for paper? These are lean times. We must choose between paper for writing and noodles for our soup. And I always choose noodles.’ She chuckles and I know the paper is yet another thing that is not real. That night, Mama slips the paper to Yelena, but she drops it on the floor. I pick it up for her, and I see that there are tiny words and numbers written all over it. I wish I could read better. I’m desperate to know what it says. Or rather, what it doesn’t say, because it’s not real. Later, when Mama has tucked us into our bed above the stove and Ushanka has wrapped herself around the top of my head, I ask Yelena, ‘What’s on the paper?’ ‘What paper?’ says Yelena. ‘The paper that isn’t real,’ I reply. Yelena stares at me, nibbling her lip, then whispers, ‘A message for the Partisans. Stuff about where the Germans have their headquarters and when their trains are travelling and where they store their ammunition.’ ‘Why?’ ‘So the Partisans can blow them up.’ Yelena grabs my arm. ‘But don’t tell anyone. It’s a secret.’ ‘What’s a secret?’ I ask. ‘The message.’ ‘What message?’ I say, my eyes wide. Yelena laughs. ‘Good boy, Sasha.’ My belly swells with pride. I know how to play this game. ‘How are your knots coming along?’ asks Yelena. ‘Good! Yesterday, I crept into the dairy and tied knots in the apron strings of all the girls who were milking and only one of them noticed. Today, I tied Olga’s ankles together with Mama’s embroidery thread and just now, while you were taking a bath, I tied the sleeves of your blouse together in an enormous knot.’ Yelena rolls her eyes, then says, ‘I’ll see if I can find you some rope for practising.’ ‘Practising what?’ I ask. ‘Your knots,’ she says. ‘What knots?’ Yelena, my big sister who is twelve and always serious t

Ostinato Music Definition Ostinato (plural – ostinati or ostinatos) is an Italian word meaning obstinate or persistent and is used in music to describe a musical phrase or rhythm that is repeated persistently. The repeated pattern could be a melody, a figure in the bass – called a basso ostinato or simply a repeated rhythmic idea. An ostinato may be played for an entire piece of music or just during one section. The key aspect to remember in the definition of an ostinato is that it is a pattern that is repeated persistently in a piece of music. Rhythmic Ostinato A rhythmic ostinato is a rhythmic pattern that is persistently repeated. It will often be played on an untuned percussion instrument (e.g. snare drum, triangle, etc..). However, rhythmic ostinati can also be found in parts played on pitched instruments where the note pitch stays the same or where the pitches change as the phrase is repeated. The key characteristic is that it is the rhythm that is persistently repeated.In Maurice Ravel’s “Bolero” the use of a rhythmic ostinato brings a magical and almost hypnotic feel to the piece as the percussive pattern contrasts with the sweeping and almost improvisatory nature of the flute melody. Have a look at the pattern below and listen to its use in the audio extract: Rhythmic Ostinato Example from Ravel Bolero.A rhythmic ostinato is an excellent technique that composers use for creating drama and tension. One of the most famous examples of this is from “Mars” by Gustav Holst. Have a look/listen to the rhythmic pattern: Rhythmic Ostinato Example from Gustav Holst Mars. This rhythmic pattern is played relentlessly throughout the piece and forms the basis for the intense drama associated with the subject – Mars, the god of war! Have a listen to this extract of the piece performed by the United States Air Force Band:You can hear how the relentless sound of a rhythmic ostinato is extremely effective at building tension as the music around it changes and develops. This effect is heightened in the extract from Mars as the bass note remains on a G throughout the extract and acts as a pedal point. Not surprisingly, rhythmic ostinati are used widely in dramatic film music. Hans Zimmer is a film composer who makes considerable use of this technique across the many film scores he has written. Have a listen to the opening from his theme for the film “Pirates of the Caribbean” performed by the Auckland Symphony Orchestra:You can hear that there are a number of different ostinati in many of the different parts that are layered to produce the overall sound. Here is the rhythmic ostinato that forms the basis of the melody line: Rhythmic Ostinato Example Hans ZimmerMelodic ostinato A melodic ostinato is a repeated pattern where both the rhythm and the melody form the basis for the repeated pattern. These often occur in the bass part where they are called a basso ostinato. Basso Ostinato A basso ostinato is a repeated pattern in the bass part of a piece. This technique became particularly popular in the 17th century where a number of Baroque dances were based upon ostinati in the bass part. In dances such as the passacaglia the bass remained constant throughout the piece whilst the other parts developed. This technique is called “ground bass” and you can have a look at my lesson on ground bass for some examples of this. The most famous example of a basso ostinato is Pachelbel’s Canon in D. Ostinati Examples in Contemporary Music Rhythmic and melodic ostinatos have had a massive influence on contemporary popular music across a wide range of genres. This can be seen in 2 main ways: Riffs (short melodic phrases) – these are effectively contemporary expressions of ostinato. Loops – rhythmic and melodic phrases are repeated to create the characteristic sound of contemporary productions. As a result, you will probably be able to find examples of the use of repeated patterns/ostinati in most contemporary songs. However, there are some songs where the use of an ostinato provides the clear foundation for the song and these are useful examples to listen to. Examples of Ostinati Riffs Seven Nation Army by White Stripes The guitar riff from Seven Nation Army is one of the most famous modern guitar riffs and is used as an ostinato that plays throughout the song. It is an excellent example of a melodic ostinato:Back in Black by AC/DC The opening guitar riff in this song is another great example:Examples of Loops Loops are repeated patterns that are clearly built on the concept of ostinati. They are used widely in contemporary music. Hip hop songs often use loops as the foundation for the track. Still D.R.E by Dr. Dre ft. Snoop Dogg In this song a piano loop plays throughout the whole track and forms the foundation of the song:

What is an official invitation letter? The companies write a letter of invitation-business when they host business visitors from abroad or from the same region or country. The business visitors can be investors; potential buyers may be conference visitors, business partners, employees of any company, or mere individuals who come for training at the company’s facilities. If a company is inviting any visitor, a representative of that company must write the letter. Also, the firms must have some specific people who would sign the invitation letters. These letters are very much precise, only containing the necessary information. The invitation letter should state the name of the business organization they represent and their relationship to the host (e.g., distributor, regional sales reps, etc.). The letter should articulate the planned dates of travel, and must be formatted professionally. What is a personal invitation letter? A Personal invitation letter is a letter one writes to invite people to a party or a social gathering at a very personal level. It is a formal request asking for the person’s presence at the event that is going to take place. All the relevant details regarding the event like the reason, date, time and venue and the dress code, if any, must be provided in the invitation letters. This will keep the guests informed, and they will feel happy to attend the event. The style and tone of the letter would depend upon the relationship between the sender and receiver. Through the letter, you should be able to make the receiver feel that you highly value his/her presence at the party or the event. A personal invitation letter can be written to invite a person to a birthday party, wedding, conference, meeting, dinner, etc. Before writing the letter, make sure you have a list of people whom you would like to invite to the party or the event. How to Write an Invitation Letter Writing an invitation letter becomes easy and swift once you get through the tips and the format of the invitation letter provided below. Usually block, semi-block or a modified block format is used for official invitation letters. The important aspects of any invitation letters are date, time, salutations and closing. For more advice refer to the tips provided. Tips for Invitation Letter Writing ● Organize the Matter – Before you draft an invitation letter ensure that you have all the required material. This material refers to a list of the people to be invited, sequential order of the events, timings of the events, special guest, official documents, photocopies and any other required item. Some items may also need to be attached along with the letter, keep them alongside. Refer to these as and when required. All the relevant documents will help you in drafting the letter. ● Drafting – You don’t just write a letter straightway and post it. It has to be reviewed and finalized. One of these processes is drafting. Drafting ensures that your mistakes and their rectification aren’t passed on to the invitation itself. Make all the mistakes in the draft itself. Drafting an invitation letter is important as sometimes we may make mistakes that we are not able to see but they are visible to others. One may require a draft to be approved by seniors before it is finalized. A second opinion from a friend or peer etc. may be required as well to determine certain things. ● Politeness – You don’t need to be told that you have to use polite language while writing an invitation letter, why would you be rude when sending an invitation? True, but you have to remind yourself of certain manners and etiquettes required of an invitation. Your invitation is your initiative, not the recipients so you need to be gracious. Always begin the letter with a welcome note instead of straightforward information of the invitation. Words of respect and gratitude are symbols of courtesy and politeness, always expressing your gratitude in the beginning and the end of the letter. ● Positive Tone – The gesture of welcome and gratitude themselves are positive points of an invitation letter. Apart from these, gestures of appreciation and anticipation are other positive points which can persuade a guest to attend the event. When you show your appreciation and anticipation towards the recipient through your words, it is an acknowledgement of his importance and thereby a positive approach. Towards this effect two tenses are used within the invitation letter, the present and the future. The present tense conveys information about the event and the future tense conveys an anticipated presence of the guest. ● Offer Assistance – An invitation being the responsibility of the sender, the assistance to the recipient by default becomes a responsibility of the host. The more facilities you provide the better the chances of someone’s attendance. You can offer pick up and drop services, accommodation, meals, provide them contact numbers in case you are not present at the venue and other required assistance. Relevant facts like date, time and venue of the event in the beginning itself is itself assisting. These assistances encourage a positive response from the invitees. ● Special Instructions – Some occasions require special instructions for the guests. These instructions can be: 1. Dress code 2. Road or route map 3. Purpose of the occasion – birthday, honor, anniversary etc. 4. Return gift 5. Response or confirmation to the invitation 6. Attire and items required for the guest to bring 7. No eatables allowed 8. Entrance only by invitation 9. 2 people per pass 10. No weapons allowed ● Length of the Matter – A simple invitation letter will only contain only the relevant facts. A simple invitation letter features an introduction which allows the sender to introduce themselves and or the organization they represent. A simple background of the individual or company is enough. Though invitations are meant to be concise and straightforward, it isn’t necessary. You can vary the length as per your need and requirement. Wedding and party invitation letters are not lengthy as compared to visit and certain personal invitation letters. ● Using Letterhead – As a rule official Invitation letters require a letterhead. Letterhead represents the sender and its inclusion is authority established. If you have a pre printed letterhead then use that. Personal Invitation letters don’t require letterheads and one can use it as per one’s desire. ● Gesture of Appreciation – Next, the appreciation for the guest to attend an activity or event must be shown. This can be completed with a formal note, stating that you look forward to seeing the individual at the event. ● Don’t forget the Enclosure – Some requests require certain documents to be attached; these can be the photocopies of documents like agreements, hard copies of email received, earlier correspondence, receipts, warranty etc. Keep original copies of all your letters, faxes, e-mails, and other related documents. ● Closing the Letter – Start the letter with Gratitude and end it with the same. It is a professional and social courtesy. At the end of your last paragraph is written, a complimentary close of the likes of ‘Sincerely’, ‘Thank you’, ‘Truly’ is essential. Close the letter by restating your appreciation and gratitude. ● Proofreading – Check for - awkward phrases, grammatical errors, incomplete sentences and spelling mistakes. Fix them with appropriate punctuation and remove dull or lifeless sentences and replace them with clever phrasing, poetry or a themed approach. This is the final step; the draft will be reviewed and revised before it acquires a proper form. Read it aloud to yourself to figure out mistakes which are missed out in writing. ● Inform in Advance – Invitation letters need to be sent in advance. Try to send the invitation letter two weeks or more in advance. The recipient needs to know in advance so that they can adjust their schedules, book tickets or make other arrangements which are essential.

The following days are a jumble of gunfire, digging, gobbled food, soldiers running in and out of the forest in small groups, distant explosions, stray shells, bandaged heads and unexpected lulls. On the very first day, before dawn, I am ordered into one of the newly dug trenches. I huddle there, squeezing my magic buttons and singing songs to the dog. When the fighting stops, the dog disappears, but a new companion takes his place. A strange little soldier crawls along the trench toward me. ‘Private Sasha!’ he cries. ‘I’ve been looking for you all day long!’ He’s old, like a grandfather, a dedushka. He has a black patch over one eye, a tape measure around his neck and a row of pins threaded into his sleeve. Hanging from his belt is the most enormous pair of scissors I have ever seen and I wonder if he uses them as a weapon. He doesn’t tell me his name, so in my head he becomes Dedushka. Dedushka squats, cups his hand to his ear, peers over the top of the trench and smiles. ‘It’s safe to be upright . . . for now.’ He helps me to my feet, dusts me off and commands me to stand as tall and straight as I can. Then he measures me. Everything from head to toe – even my toes! He writes numbers in a little notebook, strings his tape measure back around his neck, salutes and hurries away. It’s all very strange, and I wonder if Dedushka has been bumped on the head during the battle and is now a little bit muddled. I should have given him a hug before he left. I chase after him but stop when I’m hit by a shovelful of flying dirt. Sleepy Bear is digging a cave! ‘Are you going to hibernate?’ I ask. Sleepy Bear chuckles. ‘No, although that would be wonderful! I could do with a lo-o-o-ong sleep.’ He sighs and closes his eyes. He doesn’t open them again and I realise that he has gone to sleep. Standing up! I shake his arm, and he opens his eyes and keeps talking. ‘No, I’m not hibernating. I’m digging a little nook where I can sleep and eat. I’ll hang up my raincape as a door that can open and close so it feels just like a real home . . . except for the lice . . . and the bad smells . . . and the bombs that make the walls shake and crumble.’ He points further along the trench to where other soldiers are digging. ‘We’re all making little houses in the ground.’ ‘Like rabbits and moles,’ I say. Sleepy Bear chuckles. ‘Yes! And soldiers who need to hide from German bullets and bombs.’ He stops digging to roll a cigarette. ‘Should I be making a house?’ I ask. ‘I want to hide from German bullets and bombs, too.’ Sleepy Bear flops to the ground, lights his cigarette, closes his eyes and takes a deep puff. I wait for him to answer, but, instead, he begins to snore! I poke him in the side. He snorts and he murmurs, ‘I think someone has already built you a house, Sasha. Keep going along this beautiful village street and you are sure to find it.’ He falls asleep once more. I kiss his dusty cheek and whisper, ‘Thank you, Sleepy Bear.’ A little way along, I see Cook in a cloud of smoke. He has lit a fire, right here in the middle of the trench, and is stirring a cauldron full of kasha. He squats as he stirs. ‘What are you doing?’ I ask. ‘Cooking supper, of course!’ he cries. ‘But why are you doing it here?’ Cook points his spoon at the ground above the trenches. ‘Because if I do it up there, my pot will be filled with holes from German bullets and all of the kasha will leak out onto the ground. It’s bad enough that our supplies can’t get through German lines and there’s nothing to cook but buckwheat for kasha. But if we lost the kasha, too . . .’ ‘Hungry soldiers,’ I say. Cook nods. ‘And grumpy!’ ‘Like Boris!’ I gasp. ‘Even worse,’ warns Cook. I picture the kasha pot full of bullet holes. And then I realise that if the kasha pot were full of holes, then Cook would be, too. I wrap my arms around Cook’s neck and say, ‘I think this is a very good place for cooking our supper.’ I kiss his smoky cheek and run along. At the end of the trench, I find the biggest hole of all. It’s wide and deep and as busy as a beehive in a blossom tree. Above, a group of soldiers is rolling logs into place for a roof, while below, typewriters rattle and pencils scratch and papers flutter and voices crackle out of five different radios. Their words tangle together to tell a strange wartime fairy tale about German guns and a loving father called Stalin and a Red Army regiment that is lost in the deep, dark forest and a wicked beast called Hitler and a delivery of vegetables that was hit by a bomb and blown into a million tiny pieces too small even to make soup. In the middle of it all, wrestling with a rumpled map, his rifle still slung over his shoulder, is Major Scruff. ‘Major Scruff!’ I run and jump into his arms. ‘Is this our new home?’ ‘Yes, Sasha. I suppose it is.’ ‘Is it safe from German bullets and bombs?’ I ask. He stares at me. ‘Were you scared in the trenches today, Sasha?’ ‘No,’ I reply. ‘I had magic buttons and a dog and some songs to sing. Were you scared in the forest, Major Scruff?’ ‘Yes,’ he says. ‘Poor Major Scruff!’ I press my hand against his cheek. The dark, rough stubble is grubby with grit and his eyelids are taking a long time to open after every blink. ‘You need a shave and a nap!’ I scold. He chuckles. ‘I am too tired to shave and too busy to nap.’ I scrunch my nose while I consider his problem. ‘I know!’ I cry. ‘You nap and I will shave your whiskers. That will be two jobs tumbled into one!’ And so that’s what we do. Major Scruff slumps into a chair and snoozes while I lather his face with soapy water and shave his whiskers. The soap suds travel from his face, up into his hair and down the front of his uniform, and I have to shave his jaw and chin three times because I keep missing bits, but I finally get it all done. I am just wiping his cheeks dry when the dog appears. He licks my hand, then stretches up and licks soap suds from Major Scruff’s ear. Major Scruff wakes with a start. He feels his newly shaved face and cries, ‘Wonderful, Sasha! I feel smooth, clean, rested and ready for action.’ He ruffles my hair. ‘We must do this again tomorrow. Although next time, you might wake me with a gentle shake of the shoulder instead of licking my ear.’

Ions Ions are charged substances that have formed through the gain or loss of electrons. Cations form from the loss of electrons and have a positive charge while anions form through the gain of electrons and have a negative charge. Cation Formation Cations are the positive ions formed by the loss of one or more electrons. The most commonly formed cations of the representative elements are those that involve the loss of all of the valence electrons. Consider the alkali metal sodium (Na) . It has one valence electron in the n=3 energy level. Upon losing that electron, the sodiu ion now has an octet of electrons from the second energy level and a charge of 1+ . The electron arrangement of the sodium ion is now the same as that of the noble gas neon. Consider a similar process with magnesium and aluminum. In this case, the magnesium atom loses its two valence electrons in order to achieve the same arrangement as the noble gas neon and a charge of 2+ . The aluminum atom loses its three valence electrons to have the same electron arrangement as neon and a charge of 3+ . For representative elements under typical conditions, three electrons is usually the maximum number that will be los. Representative elements will not lose electrons beyond their valence because they would have to "break" the octet of the previous energy level which provides stability to the ion. Anions Anions are the negative ions formed from the gain of one or more electrons. When nonmetal atoms gain elections, they often do so until their outermost principal energy level achieves an octet. For fluorine, which has an electron arrangement of (2, 7), it only needs to gain one electron to have the same electron arrangement as neon. Forming an octet (eight electrons in the outer shell) provides stability to the atom. Fluorine will gain one electron and have a charge of 1− . The electron arrangement of the fluoride ion (2, 8) will also change to reflect the gain of an electron. Oxygen has an electron arrangement of (2, 6) and needs to gain two electrons to fill the n=2 energy level and achieve an octet of electrons in the outermost shell. The oxide ion will have a charge of 2− as a result of gaining two electrons. Under typical conditions, three electrons is the maximum that will be gained in the formation of anions. Subatomic Particles in an Ion Since ions form from the gain or loss of electrons, we can also look at the number of subatomic particles (protons, neutrons, and electrons) found in an ion. Remember that the number of protons determines the identity of the element and will not change in a chemical process. Example 2.5.1 How many protons, neutrons, and electrons in a single oxide (O2−) ion? Solution Oxygen has the atomic number 8 so both the atom and the ion will have 8 protons. The average atomic mass of oxygen is 16. Therefore, there will be 8 neutrons (atomic mass−atomic number=neutrons) . A neutral oxygen atom would have 8 electrons. However, the anion has gained two electrons so O2− has 10 electrons. We can also use information about the subatomic particles to determine the identity of an ion. Example 2.5.2 An ion with a 2+ charge has 18 electrons. Determine the identity of the ion. Solution If an ion has a 2+ charge then it must have lost electrons to form the cation. If the ion has 18 electrons and the atom lost 2 to form the ion, then the neutral atom contained 20 electrons. Since it was neutral, it must also have had 20 protons. Therefore the element is calcium. Polyatomic Ions A polyatomic ion is an ion composed of two or more atoms that have a charge as a group (poly = many). The ammonium ion (see figure below) consists of one nitrogen atom and four hydrogen atoms. Together, they comprise a single ion with a 1+ charge and a formula of NH+4 . The hydroxide ion (see figure below) contains one hydrogen atom and one oxygen atom with an overall charge of 1− . The carbonate ion (see figure below) consists of one carbon atom and three oxygen atoms and carries an overall charge of 2− . The formula of the carbonate ion is CO2−3 . The atoms of a polyatomic ion are tightly bonded together and so the entire ion behaves as a single unit. The figures below show several examples. Soult Screenshot 2-2-1.png Figure 2.5.1 : The ammonium ion (NH+4) is a nitrogen atom (blue) bonded to four hydrogen atoms (white). Soult Screenshot 2-2-2.png Figure 2.5.2 : The hydroxide ion (OH−) is an oxygen atom (red) bonded to a hydrogen atom. Soult Screenshot 2-2-3.png Figure 2.5.3 : The carbonate ion (CO2−3) is a carbon atom (black) bonded to three oxygen atoms. The table below lists a number of polyatomic ions by name and by structure. The heading for each column indicates the charge on the polyatomic ions in that group. Note that the vast majority of the ions listed are anions - there are very few polyatomic cations. 1− 2− 3− 1+ Table 2.5.1 : Common Polyatomic Ions acetate, CH3COO− carbonate, CO2−3 arsenate, AsO3−3 ammonium, NH+4 bromate, BrO−3 chromate, CrO2−4 phosphite, PO3−3 chlorate, ClO−3 dichromate, Cr2O2−7 phosphate, PO3−4 chlorite, ClO−2 hydrogen phosphate, HPO2−4 cyanide, CN− oxalate, C2O2−4 dihydrogen phosphate, H2PO−4 peroxide, O2−2 hydrogen carbonate, HCO−3 silicate, SiO2−3 hydrogen sulfate, HSO−4 sulfate, SO2−4 hydrogen sulfide, HS− sulfite, SO2−3 hydroxide, OH− hypochlorite, ClO− nitrate, NO−3 nitrite, NO−2 perchlorate, ClO−4 permanganate, MnO−4 The vast majority of polyatomic ions are anions, many of which end in -ate or -ite. Notice that in some cases such as nitrate (NO−3) and nitrite (NO−2) , there are multiple anions that consist of the same two elements. In these cases, the difference between the ions is the number of oxygen atoms present, while the overall charge is the same. As a class, these are called oxyanions. When there are two oxyanions for a particular element, the one with the greater number of oxygen atoms gets the -ate suffix, while the one with the fewer number of oxygen atoms gets the -ite suffix. The four oxyanions of chlorine are shown below, which also includes the use of the prefixes hypo- and per-. ClO− , hypochlorite ClO−2 , chlorite ClO−3 , chlorate ClO−4 , perchlorate Not your usual ion Soult Screenshot 2-2-4.png "Drink you milk. It's good for your bones." We're told this from early childhood, and with good reason. Milk contains a good supply of calcium, part of the structure of bone. However, there are two other ionic components of hydroxyapatite, the mineral component. Phosphate ion and hydroxide ion make up the remainder of the inorganic material in bone. News You Can Use Bone is a very complex structure. It is composed of protein (mainly collagen), hydroxyapatite (a calcium-phosphate-hydroxide mixture), some other minerals, and contains 10 - 20% water. The calcium/phosphate ratios are not stoichiometric, but vary somewhat from one portion of bone to the next. Bones are very strong but will break under enough stress. Regular exercise and proper nutrition help to increase bone strength. Watch a video about bone structure at http://www.youtube.com/watch?v=d9owEvYdouk Nitrate is an anion with a complex bonding structure. Major sources for this ion in drinking water are runoff from fertilizer, septic tank leakage, sewage, and natural deposits. High concentrations of nitrates represent a significant health hazard, especially to infants. The nitrate in the body is converted to nitrite, which then binds to hemoglobin. This binding decreases the ability of hemoglobin to transport oxygen, thus depriving the cells of the O2 needed for proper functioning. Cyanide production is widespread throughout nature. Forest fires will produce significant amounts of cyanide. Many plants contain cyanide, and it is produced by a number of bacteria, algae, and fungi. Cyanide is used industrially in metal finishing, iron and steel mills, and in organic synthesis processes. This material is also an important component for the refining of precious metals. Formation of a complex between cyanide and gold allows extraction of this metal from a mixture.

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