Reading the Periodic Table:Element Squares

Atomic Structure

Nucleus

Electron Cloud

Atomic StructureElectrons

Protons

Neutrons

Protons• In the nucleus• A Positive(+)

charge• Mass = 1 a.m.u• Determine the

element• Determine the

atomic number

Protons

Protons and P. Table

Atomic # = a whole #

Atomic # = # protons

Electrons• In electron cloud• In Unbound atom

are equal in number to protons

• Negatively charged

• Mass=1/1800 amu

e

e

Electrons and P. Table

The atomic # = # protons

Atoms not involved in bondshave the same number ofelectrons as protons.

Atomic # can be used toInfer the number of electrons

Neutrons• In the nucleus• No charge

(neutral)• Mass = 1 a.m.u.• “glue” nucleus

together

Neutrons and P. Table

All the mass of an atomIs found in the nucleus

Only protons and neutronsconsidered to have mass

Calculate # neutrons from Atomic mass

Neutrons and P. TableAtomic mass - Atomic # = # neutrons

1. Round atomic mass to nearest whole number

Ex. # neutrons in helium

Atomic mass = 4.006 =4 Atomic # = 2

4 - 2 = 2 neutrons

Test yourself• Element name?

• Gold• # protons?

• 79• # electrons?

• 79• # neutrons?

• 118

Au196.979

FamiliesColumns = Families (or groups)

•Family members share common properties

Periods• Period = Row

• Row number = # energy levels ( shells)