| 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 (amu) | 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 |
| 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, tiny) NEGATIVELY CHARGED particle found OUTSIDE the nucleus |
| Electron Configuration | 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 |
| 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 sum of the masses of protons and neutrons |
| Neutron | subatomic particle with a MASS of 1 amu (atomic mass unit), and a CHARGE of zero found WITHIN THE NUCLEUS; (NEUTRAL) |
| 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, POSITIVE, core of an atom |
| Orbit | set paths that electrons take around nucleus according to Planetary/Bohr Model |
| Orbital | a region where electrons of an atom can be found according to Wave-Mechanical Model |
| Planetary Model (aka :Bohr Model") | proposed that electrons are found in well-defined orbits/paths around nucleus |
| Proton | subatomic particle with a MASS of 1 amu (atomic mass unit), and a CHARGE of +1 found WITHIN THE NUCLEUS |
| Quantum Theory | used to describe the dual nature of matter; electrons behave like particles and energy |
| Valence electrons | 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 |
