Atomic StructureNucleus – contains protons and neutrons

Electron Cloud – area where electrons are found

Neutron – particle with no charge

Proton – positively charged particle

Quarks – particles that make up protons and neutrons

6

C12.0Carbon

Atomic Number- the number of protons

- usually the smallest number

Chemical Symbol

Element Name

Atomic Mass- usually the largest number

Atomic Number – the number of protons in an individual atom◦examples:

Hydrogen : 1 proton Oxygen : 8 protons

Mass number – the total of protons and neutrons in an atom◦# of neutrons = mass number – atomic

number◦examples:

Carbon-12 - 6 protons, 6 neutrons Oxygen-17 – 8 protons, 9 neutrons

Isotopes – atoms of the same element that have different numbers of neutrons◦For example,

Atomic Mass – the weighted average of the masses of all the naturally occurring isotopes of an element◦amu – atomic mass unit – unit for atomic

mass Each proton and neutron has a mass of

approximately 1 amu

◦example – Chlorine-35 makes up 76% of all chlorine in nature, and chlorine-37 makes up the other 24%:

(35 x 0.76) = 26.60(37 x 0.24) = 8.88

35.48 amu