Prentice Hall Chemistry Chapter 4

atom

the smallest particle of an element that retains its identity in a chemical formula

Democritus

believed that atoms were indivisible and and indestructible

Dalton

Atomic Theory - Atoms of the same element are identical. atoms can be combined into whole number ratios

electrons

negatively charged, floating around nucleus. number is the same as protons

protons

positively charged. inside the nucleus, same number as atomic number

neutrons

no charge, inside nucleus. atomic mass - proton = # of neutrons

nucleus

tiny central core of an atom composed of protons and neutrons. positively charged

Rutherford

gold foil experiment - atoms are made up if mostly empty space with a small dense nucleus in the center

Thomson

cathode ray, discovered that electrons have a negative charge.

Bohr

proposed that an electron is found only in orbits, around nucleus

period

the horizontal rows on a periodic table

group

each vertical column of the periodic table

atomic mass unit

(AMU) unit used when finding relative abundance

Isotopes

atoms that have the same number of protons but different number of neutrons