Terms to Know

Valence Electrons

Electrons in the outermost shell of an atom that are involved in bonding

Covalent Bond

A bond where atoms share electrons

Single Bond

Two atoms share 1 pair of electrons (2 electrons total)

Double Bond

Two atoms share 2 pairs of electrons (4 electrons total)

Triple Bond

Two atoms share 3 pairs of electrons (6 electrons total)

Chemical Properties

How a substance reacts or behaves in chemical reactions

Ionic Bond

A bond where electrons are transferred from one atom to another, forming charged ions

Polar Covalent Bond

A covalent bond where electrons are shared unequally, creating partial charges

Nonpolar Covalent Bond

A covalent bond where electrons are shared equally

Metallic Bond

A bond between metal atoms where electrons move freely in a “sea of electrons

Homogeneous

A mixture that is evenly mixed throughout

Heterogeneous

A mixture that is not evenly mixed; you can see different parts

Neutral Atom

An atom with equal numbers of protons and electrons, so it has no overall charge

Lewis Symbol (Lewis Structure)

A diagram that shows an atom’s valence electrons as dots around its symbol

Period

A row on periodic table

Group

A column on the periodic table. Elements in a group have similar properties

Compound

A substance made of 2 or more different elements chemically bonded together

Protons

• Positively charged particles in the nucleus

• How to find: The atomic number = number of protons

Electrons

• Negatively charged particles outside the nucleus

• How to find (neutral atom): Electrons = atomic number
  (Because electrons = protons in a neutral atom)

• If it’s an ion:

  • Subtract electrons for a positive charge

  • Add electrons for a negative charge

  • Na⁺ → 11 protons, 10 electrons

  • Cl⁻ → 17 protons, 18 electrons

Neutrons

• Neutral particles in the nucleus

• How to find: Mass number − atomic number = neutrons

(Remember: mass number = protons + neutrons)