Ions and Ionic Compounds

Simple Ions

Chemical Reactivity – How much an element reacts depends on the electron configuration of its atoms.› Ex: O and Ne

Noble gases are least reactive. Alkali metals and halogens are most

reactive. WHY?

Valence Electrons

Group number tells you how many electrons are in an element’s valence shell.

Atoms gain and lose electrons to become stable.

Characteristics of Stable Ions

An atom and its ion have different chemical properties. › Stable ion should not be confused with

noble gas Has a charge now and forms a compound.

Atoms and Ions

Atoms of metals & nonmetal elements form Ions differently.› Almost all metals form cations

Ex: Mg – 1s2 2s2 2p6 3s2 Takes less energy to lose 2 electrons, than gain 6.

Nonmetals form anions› Ex: O – 1s2 2s2 2p4› Gaining 2 electrons requires less energy than

losing 6.

Ionic Bonding & Salts

Form between ions of opposite charges (+ & -). › Compound becomes electrically neutral. › Ex: NaCl

Ionic Bonding & Salts

Ionization energy – energy needed to remove the outermost electron from an atom.

Endothermic – Needs energy to be put in the reaction in order for the reaction to occur.

Exothermic – Reaction releases energy (often heat).

Ionic Bonds

Strong Have high melting/boiling points Rarely gas at room temp. When dissolved conduct electric

current. Salts are hard and brittle.

Names and Formulas:

Simple Ions:› Cation borrows name of element: K is

potassium ion.› When element forms 2+ ions, roman

numerals are used: Ex: Cu+ : copper (I) ion

Cu 2+ : copper (II) ion

› Anion also uses element name but, add ide to end. Ex: chloride, oxide

Naming a compound

Cation name followed by anion› Ex: NaCl sodium chloride› Ex: Mg3N2 magnesium nitride› Ex: K2 potassium oxide

Writing ionic formulas

Must have no overall charge (neutral).› Ex: Mg 2+ and N3-

Naming Polyatomic Ions

Presence of Oxygen – ite and -ate. The one with less O is ite, while the one with more O is ate.› Ex: SO3

2- is sulfite SO42- is sufate

Naming of Polyatomic Ions

Presence of hydrogen indicated by using hydrogen.

Prefixes are used to indicate how many hydrogen› Ex: H2PO4

2- : dihydrogen phosphate.

MUST KNOW: CO32- , OH- , NO3

- , NO2- ,

phosphate, sulfate, sulfite.

Naming Compounds w/ Polyatomic Ions

K2 CO3

Name cation: name of the element. Name anion: what is the charge? Write it out Potassium carbonate