CH. 8 | Atoms and Periodic Properties

Atoms | Dalton’s Atomic Theory

Indivisible atoms

• Cannot be cut

• All matter = indivisible atoms

• An element is made up of identical atoms

• Different elements have atoms with different masses

• Chemical compounds are made of atoms in specific integer ratios

• Atoms are neither created nor destroyed in chemical reactions

Electron’s charge-to-mass ratio

Atomic Number

• # of protons in the nucleus

• Elements distinguished by atomic #

• # of protons = # of electrons in neutral atoms

Isotopes

Same # of protons, different # of neutrons

Nuclear Notation

Periodic Table Notation

Mass Number

Number of protons + neutrons

Atomic Mass Unit

1/12 of carbon - 12 isotope mass

Atomic Weight

Atomic mass of an element, averaged over naturally occurring isotopes

Quantum Mechanics

…

Electron Configuration

Arrangement of electrons into atomic orbitals

• When writing them, electrons fill available orbitals in order of increasing energy

Periodic Table (Understand / Take info from it)

• Periodic Chemical Properties
  → Rows = Periods
  ↓ Columns = Families or Groups

• Electrons in outer orbits determine chemical properties

• Valence electrons = Roman Numerals

• Alkali metals (IA)

• Alkaline earths (IIA)

• Halogens (VIIA)

• Noble gases (VIIIA)

Metals, Nonmetals, Semiconductors