Chem Unit 1

Democritus

Greek Philospher, first to suggest atoms, not widely excepted

John Dalton

studied gases, based on expiremental evidence, indivisible

J.J. Thomxon

English Physicst, sphere positively charged matter and electrons

Earnest Rutherford

chemist, nucleus, protons neutrons electrons

Atomic number

number of protons, all of element have same, different elements different

Atoms are neutral so

each + is balanced by a - charge

protons equals the number of

electrons

Mass number

protons + neutrons in nucleus

neutrons is the difference between

mass number - atomic number

Shorthand the atomic number is

subscript (below)

The mass number is

superscript (above)

isotopes have the same number of

protons

isotopes have different numbers of

neutrons

isotopes have different atomic number or mass

mass number

Weighted average=

(realtive abundance of A)(mass of A) +(realtive abundance of B)(mass of B)

Neils Bohr

focuses on electron arrangement, electron orbits and energy jumps

electrons have a fixed amount of