Ionic Compounds and Metals Chapter 7

Ion Formation Ions are charged atoms. An neutral atom becomes an ion when it either gains or loses electrons. The imbalance between the number of protons and the number of electrons results in a charge on the atom. An ion with a positive charge is called a cation. An ion with a negative charge is called an anion.

The Octet Rule The octet rule states that atoms tend to lose, gain, or share electrons in order to acquire a full set of eight valence electrons.

Formation of Ionic Bonds The electrostatic force that holds two ions together is called an ionic bonds. compounds that contain ionic bonds are called ionic compounds. Na + Cl  Na+ + Cl- [Ne] 3s1 + [Ne] 3s23p5  [Ne] + [Ar]

Structure of Ionic Compounds Most ionic compounds have a crystal like structure. This structure is known as a crystal lattice.

Dissolved Ionic Compounds When ionic compounds are dissolved in water they break apart into a cation and an anion. Not all ionic compounds dissolve in water. Ones that do are called electrolytes.

Names and Formulas of Ionic Compounds The chemical formula for an ionic compound, called a formula unit, represents the simplest ratio of ions involved. MgCl2 A monatomic ion is a one-atom ion.

Common Ions and their charges Representative elements of the same groups usually have the same ionic charges. Group 1: H+, Li+, Na+ Group 2: Be2+, Mg2+, Ca2+ Group 15: N3-, P3-, As3- Group 16: O2-, S2-, Se2- Group 17: F-, Cl-, Br- Transition elements can usually have more than one charge. Example Fe2+ and Fe3+

Transition Metal Ions Most transition metals can have a few different charges. Example: Fe2+, Fe3+ Fe2O3 FeO

Polyatomic Ions Polyatomic ions are ions that are made up of more than one atom. There are a few you need to memorize….sorry. Ammonium: NH4+ Nitrite: NO2- Nitrate: NO3- Hydroxide: OH- Hypochlorite: ClO-

Chlorite: ClO2- Chlorate: ClO3- Perchlorate: ClO4- Carbonate: CO32- Sulfite: SO32- Sulfate: SO42- Peroxide: O22- PO43-

Naming Ionic Compounds The cation comes first in the name then the anion. If the anion is a monatomic ion we give it the ending –ide. NaCl – Sodium Chloride When the formula unit contains two or more of the same polyatomic ion we put it in parentheses with a subscript to show how many ions are present. Ba(NO3)2 – Barium Nitrate If the cation is a transition element the charge of the cation is written as roman numerals in parentheses. Co(SO4) – Cobalt (II) Sulfate

Practice NH4Cl Fe(NO3)3 TiBr3 Pb(SO4)2 Chromium (VI) Phosphate Tin (II) Nitrate Cobalt (III) Oxide Chromium (III) Hydroxide