chem

significant figures

come from the measurement process; they include the certain digit(s) plus the estimated digit.

Variability

is a measure of how spread out (or "scattered") the numbers are in a set of numbers.

Accuracy

is how close an experimental measurement is to the accepted value.

percent error formula

a metric commonly used to quantify accuracy. In my class the formula is:100 x (experimental value - accepted value) / accepted value

matter

is anything that has mass and occupies three-dimensional space.

mass number

the total number of protons and neutrons in the nucleus of that atom.

isotope

are atoms of the same element that have different numbers of neutrons.

relative abundance

is the percentage of a particular isotope that would be found in a representative sample of the element in nature.

atomic mass

is the weighted-average of the isotopic masses of the stable isotopes of an element.

atom

is the smallest unit of matter that retains the chemical properties of that element.

molecule

A discrete collection of two or more atoms held together by chemical bonds.

compound

is a substance composed of two or more elements that can only be broken down into simpler substances using chemical means (i.e., not by physical means).

Mixture

is a form of matter composed of two or more substances. The component substances can be separated from one another using physical means.

ion

is an atom, or group of atoms, that has a net charge.

Cation

positive ion

anion

negative ion

monoatomic ion

an ion formed from a single atom

polyatomic ion

an ion made of two or more atoms

molar mass

the mass of one mole of a substance

Avogrado's number (mole)

6.022 x 10^23