Question | Answer |
Law of definite proportions | compounds are made of the same elements in the same proportions regardless of size or source of sample |
Law of conservation of mass | mass cannot be created or destroyed
Cathode ray tube.) |
Nucleus | Dense, central portion of the atom. Holds all the positive charge. Nearly all the mass, but little volume. (Gold foil experiment) |
Proton | a subatomic particle with a positive charge; found in the nucleus of an atom. The number of protons in the nucleus is the atomic #, which determines the identity of an element |
Neutron | a subatomic particle that has no charge and is found in the nucleus. (James Chadwick) |
Atomic number | the number of protons in the nucleus of an atom. (never changes for that element) Must be whole numbers. Tells how many electrons are present. |
Mass Number | the total number of protons and neutrons of the nucleus of an atom. |
Isotope | an atom that has the same number of protons as other atoms of the same element but has a different name and a different number of neutrons. |
Orbital | regions around a nucleus that correspond to specific energy levels; electrons are likely to be found here |
Electromagnetic Spectrum | all of the frequencies or wavelengths of electromagnetic radiation |
Ground State | normal energy level for electrons. |
Excited State | more energy than normal. |
Quantum Number | a number that specifies the properties of electrons |
Pauli Exclusion Principle | The principle that states that 2 particles of a certain class cannot be in the exact same energy state. |
Electron Configuration | the arrangement of electrons in an atom |
Aufbau Principle | Electrons fill orbitals that have the lowest energy first. |
Hund’s Rule | Fill each orbital of an energy level with one electron before putting a second electron in the orbital |
Atomic mass | mass of atoms is measured in atomic mass units. (amu) Atomic mass on periodic table is the average of all the isotopes. |
Mole | (mol) the SI unit for measuring the amount of a substance whose # of particles is the same as the # of atoms. In a 12-g sample of carbon -12 |
Molar mass | (g/mol) the mass in grams of 1 mol of a substance |
Avogadro’s Number | 1 mol= 6.02*10^23 atoms |
Electron | A subatomic particle that has a negative electric charge. (J.J. Thomson’s Cathode ray tube.) |