Unit 2

a pure substance that cannot be broken down by chemical means into other substances Think periodic table

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elements that comprise the cast majority of every living cell

essential elements other than C,H, O, or N.

elements that are required in small amounts

the smallest possible piece of an element that retains the characteristics of the element; a particle of mater

proton, neutron, electron

subatomic particle that carries a positive charge (+)

subatomic particle that carries no charge

subatomic particle that carries a negative charge (-)

protons and neutrons that form the center of an atom (makes up most of the mass, but very little of the volume)

the number of protons in the nucleus

an atom that has gained or lost electrons and has either a positive or negative charge

the total number of protons and neutrons in its nucleus

an of the forms of an element,, each having a different number of neutrons

the average mass of all the isotopes

when unstable isotopes emit energy as rays or particles when they break down into more stable forms

two or more chemically joined atoms

a molecule composed of two or more different elements (i.e. Na (sodium) + Cl (Chlorine) = NaCl (sodium chloride [table salt])

volume of space where a particular electron is likely to be

a group of orbitals that share the same level

the outermost occupied energy shell of an atom

the attractive force that holds atoms together

chemical bond in which two atoms share electrons