concept 2.1: matter consists of chemical elements in pure form and in combinations called compounds

define matter

makes up anything that takes up space and has mass

element

a substance that cannot be broken down to other substances by chemical reactions

compound

a substance consisting of two or more elements in a fixed ratio

what are the 4 most important elements of life

carbon, oxygen, hydrogen , nitrogen

charge of neutrons, protons, and electrons

neutrons- no charge

protons- positive charge

electrons- negative charge

isotope

two atoms of an element that differ in the number of neutrons

redioactive tracers

radioactive isotopes often used as diagnostic tools in medicine

radiometric dating

a "parent" isotope decays into its "daughter" isotope at a fixed rate, expressed as the half-life of the isotope

define energy

the capacity to cause change

the lower the shell for an electron results in what

lower potential energy of electrons

what does it mean for an element to have a full valence

the element is non reactive

how many electrons can occupy a single orbital

no more than two

define potential energy

the energy that matter possesses because of its location or structure