《化学的基本内容英文版.ppt

Early Chemistry Early Chemists only believed in 1 element: Dirt Later Chemists believed in 4 elements: Air Earth Fire Water Various combinations of these produced various compounds Basic Chemistry All Matter in universe is composed of Atoms Elements are composed of only 1 type of atom. Atoms are mostly empty space. Atoms have Electrons which are very small and are negatively charged and have a negligible mass (mass = 0). Electrons move in orbits around the center of the atom - in relatively distinct areas called Energy Levels.(aka. Orbits or shells) The farther from the center an electron is the more energy it has. Electrons ( therefor atoms, can gain and lose energy) and do this by moving between energy levels. Atoms have a Nucleus which contain Protons Neutrons. Protons are Positively Charged and have a mass =1 The number of protons in an atom’s nucleus determines what element it is Neutrons have no charge and are therefor called Neutral and have a mass = 1. Summary of Subatomic Particles: ? Periodic Table Notation: Chemical elements are represented on the periodic table using the following format. The letter is an abbreviation of Element Name Atomic Number is the number is the number of protons the atom has. It is the number of protons an element has which determines what element it is. Mass number is the total mass of an atom in AMU. It is the same as the number of protons neutrons of the element. One can calculate the number of neutrons an atom has by subtracting the atomic number (# protons) from the mass number. Mass number CAN change without changing the identity of the element. Isotopes: Atoms having the same atomic numbers and different mass numbers are called Isotopes Isotopes are atoms of the same element with different numbers of neutrons (mass). They react chemically the same as the “normal” form of the element They are frequently radioactive Interactions of matter: Atoms interact through the process of chemical bonding. Process is de