Matter: Everything that has mass and volume and occupies space. Molecules - All substances are made up of small units called molecules. The figure shown represents the Sphinx. The Sphinx is made of limestone rock. Limestone consists of calcium carbonate. Calcium carbonate molecules are composed of atoms. Each calcium carbonate molecule is made up of atoms. Molecules are made up of atoms. Each calcium carbonate molecule consists of atoms. Matter :Calcium carbonate substance. We have previously learned that the building unit of a living organism's body is the cell. Similarly, any substance is made up of very small building units called molecules, which are made up of even smaller units called atoms. Atom: the building unit of matter. matter molecules atoms building of atom: Scientists have made numerous attempts to discover the structure of the atom. Greek philosophers in ancient times believed that matter was made up of small, indivisible parts called Lesson.1 Atomic structure of matter Science – prep.1 First term Mrs.Maysa Zaky 2 atoms. In the early 19th century, the scientist Dalton developed the first scientific theory about the atom, in which he stated that atoms are indivisible. Rutherford's model of the atom (1909 AD) is considered the first experimental model of the atom. Scientists have determined the structure of the atom as follows: Structure of the Atom: • Nucleus: A very, very small space located at the center of the atom. It contains two types of particles: o Protons: Positively charged particles. o Neutrons: Neutral particles (no charge). • Electrons: Negatively charged particles with very little mass that revolve around the nucleus at high speeds in energy levels. Protons, neutrons, and electrons are considered subatomic particles. Measurement and Scale If we represent the size of an atom as the size of a baseball field, the size of the nucleus would be comparable to the size of the head of a pin in the middle of the field. Give reason: the nucleus has positive charge. Bec. It contains positive protons and neutral neutrons. Ernest Rutherford, the Scientist: He is a New Zealand scientist, born in 1871 A.C, He was awarded the Nobel Prize in Chemistry in 1908 and passed away in 1937. New Zealand honored him by placing his image on its highest denomination currency in recognition of his efforts in discovering the structure of the atom. A Brief Biography of a Scientist Science – prep.1 First term Mrs.Maysa Zaky 3 The atom is made up of three types of small particles, which differ from each other in symbol and electric charge and Mass. From the previous table, we can conclude that: 1. The charge of a proton is equal in magnitude to the charge of an electron, but differs in type. 2. The masses of subatomic particles are measured in atomic mass units ( U ). 3. The mass of electrons is negligible when calculating the mass of the atom due to its insignificance compared to the mass of protons or neutrons. Give reason: The mass of the atom is concentrated in the nucleus. Bec, the mass of electrons is extremely small compared to the mass of protons or neutrons within the nucleus. Give reason: Scientists have agreed to represent elements using chemical symbols to facilitate their expression and handling, especially in chemical equations. Properties of Subatomic Particles That Make Up the Atom 1/ 1836 U Relative charge Symbols of elements Science – prep.1 First term Mrs.Maysa Zaky 4 Examples of elements which have lattin name: Science – prep.1 First term Mrs.Maysa Zaky 5 Farmers use fertilizers to improve agricultural productivity. Fertilizers are chemical compounds used to improve crop yield. Fertilizers contain elements such as: • N (Nitrogen) • P (Phosphorus) • K (Potassium) • Nitrogen (N) is essential for healthy plant growth. • Phosphorus (P) helps strengthen plant roots. • Potassium (K) is necessary for the greening of plant leaves. Fertilizers are composed of three compounds containing these elements. NPK fertilizer is one of the most important types of fertilizers. Mass number A( number of nucleons): the sum of number of positive protons(P) and number of neutral neutrons(n) in the nucleus. Atomic number:Z the number of positive protons. Or the number of negative electrons(e-) Number of neutrons = mass number – atomic number A = p + n Z = p = en = A – Z