Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Atoms and Moles The Atomic Theory • As far back as 400 BC, people believed that the atomic theory existed. • The atomic theory basically stated that atoms are the building blocks of all matter. • This theory had no experimental results to back it up at the time. John Dalton • In 1808, an English schoolteacher named John Dalton used the Greek concept of the atom along with 3 other scientific laws to develop an atomic theory. • He believed that all matter was made up a few kinds of atoms. • He also stated that all elements were made up of only one type of atom and that compounds were made up of two or more types of atoms. Dalton’s Atomic Theory • All matter is composed of extremely small particles called atoms that cannot be subdivided, created, or destroyed.* • Atoms of a given element are identical in their physical and chemical properties. * • Atoms of different elements combine in simple, whole number ratios to form compounds. • Atoms of different elements differ in their physical and chemical properties. • In chemical reactions, atoms are combined, separated, or rearranged but never destroyed, created, or changed. The Laws Involved: • The Law of Conservation of Mass: The mass of reactants equals the mass of the products in a chemical reaction. Mass cannot be created nor destroyed. • The Law of Multiple Proportions: If two or more different compounds are composed of the same elements, the ratio of the masses of the second element is always the ratio of small whole numbers. • Law of definite proportions: Samples of a given compound are made with the same elements in exactly the same proportions by mass regardless of the size or the source of the samples. Electrons • Electrons were discovered in the mid-1800’s by J.J. Thompson. • The electron has a negative charge and is depicted as e,e-, 0-1 e. • It’s charge is -1.602x10 -19 C. • It’s mass is 9.109x10-31 kg. Cathode ray tube • The cathode ray tube was used by JJ Thompson to discover electrons. • Magnets or charged plates can be used to attract or deflect the beam which proved that the beam had a negative charge. Protons • Protons were discovered shortly after the electron. • The proton has a positive charge and is depicted as p,p+, or 1+1p. • It’s charge is +1.602x10-19 C. • The mass of a proton is 1.676x10-27 kg. Neutrons • Discovered by British scientist James Chadwick. • Neutrons carry no charge. They are electrically neutral. • The charge is 0 C. • They can be depicted as n or 01n. • The mass of a neutron is 1.675x10-27 kg. Gold Foil Experiment • Rutherford’s gold foil experiment surprised researchers by showing that atoms were mostly made up of space. • It also proved that atoms had a dense, positively charged area called the nucleus.