Beta Decay

a radioactive process in which a beta particle is emitted from the nucleus of an atom, raising the atomic number of the atom by one if the particle is negatively charged, lowering it by one if positively charged.

Atomic Mass Number

The weighted average mass of the isotopes of that element

Dalton’s Atomic Theory

A theory proposed by John Dalton in 1808, based on numerous scientific experiments, that marked the beginning of the development of modern atomic theory

Element

A pure substance that cannot be broken down into simpler substances by physical or chemical means

Compound

A chemical combination of two or more different elements; can be broken down into simpler substances by chemical means and has properties different from those of its component elements

Heterogeneous Mixture

One that does not have a uniform composition and in which the individual substances remain distinct

Physical Change

A type of change that alters the physical properties of a substance but does not change its composition

Chemical property

The ability or inability of a substance to combine with or change into one or more new substances