| A | B |
|---|
| Allotrope | one or more forms of an elementary substance. |
| AnION | negatively charged atom; an atom that gains an electron |
| Atom | the basic unit of structure for all matter; can’t be broken down any further by chemical means. |
| Atomic Mass | the average mass of all naturally occurring isotopes for an element |
| Atomic Mass unit (a.m.u.) | 1/12th the mass of a Carbon-12 atom; the mass of one proton or one neutron |
| Atomic number | the number of protons in an atom of a given element |
| Ex: The atomic # of carbon is 6 | which means that every atom of carbon has 6 protons in its nucleus and carbon is the only element with the atomic # 6 |
| Bohr model | atomic model constructed by Neils Bohr that proposes all electrons can be found in orbitals or paths; electrons must gain or lose energy to jump from one orbital to another |
| CatION | positively charged atom; an atom that loses an electron |
| Compound | two or more atoms of DIFFERENT ELEMENTS chemically combined; always the same ratio |
| Electron | virtually MASSLESS (teenie |
| Electron Configuration | the arrangement of electrons in an atom or molecule |
| Element | particles that all have the same number of protons in the nucleus |
| Excited state | when an atom absorbs energy and one or more of its electrons “jump” to an orbital further from the nucleus |
| Ground state | when all electrons within an atom fill the lowest energy orbitals; when the electrons are where they would “normally” be |
| Ion | a charged atom; an atom that gains or loses an electron |
| Isotope | an atom of an element with the same number of protons (atomic #) but a different number of neutrons |
| Ex: Carbon-12 (6 protons | 6 neutrons) and Carbon-14 (6 protons |
| Kernel electron(s) | any electrons found inside the valence shell; the innermost electrons |
| Lewis Dot Diagram | representation of an atom or molecule using only the element symbol and the valence electron arrangement |
| Mass number | the mass of a given isotope of an element; the sum of the masses of protons and neutrons |
| Ex: The mass number for Carbon-12 is exactly 12 amu | even though the atomic mass (average mass) of all carbon isotopes is 12.0111 |
| Neutron | subatomic particle with a MASS of 1 amu (atomic mass unit) |
| Nuclear Charge | electric charge within the nucleus of an atom; equal to the # of protons (always positive!) |
| Nucleons | any (subatomic) particle found in the nucleus of an atom; a PROTON or a NEUTRON |
| Nucleus | the DENSE |
| Orbital | a region where electrons of an atom can be found |
| Proton | subatomic particle with a MASS of 1 amu (atomic mass unit) |
| Quantum Theory | used to describe the dual nature of matter; electrons behave like particles and energy |
| Valence electron(s) | the outermost electrons in an atom; there can NEVER be more than 8 valence electrons (OCTET RULE) |
| Wave-mechanical model | states that electrons don’t travel in fixed orbits |
