Ions

Chemists have found that metal atoms transfer electrons to nonmetal atoms when they form compounds. Ions are formed when electrons are removed from or added to an atom. The rest of the atom stays the same (protons, neutrons, mass).

• The charge on an ion is noted with a superscript.
• Cations are positively charged (lose electrons)- usually formed from metal atoms
• Anions are negatively charged (gain electrons)- usually formed from nonmetal atoms

When atoms gain or lose electrons, they form ions. Ions are atoms that carry a net positive or net negative charge. (When atoms lose electrons, they have a positive charge and are called cations. When atoms gain electrons, they have a negative charge and are called anions.) Ions have electron arrangements resembling those of the noble gas atoms. Atoms tend to lose or gain electrons to attain the electron arrangement of a noble gas.

Atoms become ions to achieve the electron configuration of their nearest noble gas. In that way, atoms become more stable (lower energy state)

Ionic Compounds:

Ionic compounds form between metal atoms and nonmetal atoms. Electrons are transferred from one atom to another, forming a cation (+) and an anion (-). Cations (+) and anions (-) are attracted by electrostatic force (opposites attract).

• eg. Metal + Non-metal

Every time a metal atom and a nonmetal atom bond, they form a compound with an overall zero charge. This is known as the rule of zero charge. A compound is always neutral. Because a compound needs to be neutral, you have to add the correct number of anions or cations to balance the compound to make it neutral.

To name an ionic compound:

1. Name the cation
2. Add the anion
   1. change the ending to "-ide"

Polyatomic Ions:

Polyatomic ions contain more than one atom,. They are composed of a group of atoms with an overall positive or negative charge.. Most polyatomic ions are anions, with negative charges. The rule of zero charge can be used to predict the formulas of compounds that contain polyatomic ions. 

Each polyatomic ion has its own name. Most polyatomics are indicated by the suffixes "-ite" and "-ate". Parenthesis indicate more than one polyatomic. When naming a compound, you insert the polyatomic ion name at either the beginning or ending of the chemical name. The cation is first and the anion is second.

Transition Metals

• Transition metals have more than one oxidation state
• Charge is indicated by roman numerals (eg. Copper (II) Oxide)
  • Except: Cd²⁺, Zn²⁺, and Ag⁺