Valence Electrons Valence electrons are the electrons in the highest occupied energy level of an element’s atoms. Electron dot structures are diagrams that show valence electrons as dots.

Valence Electrons

The Octet Rule The octet rule states that in forming compounds, atoms tend to achieve the electron configuration of a noble gas.

Formation of Cations

Formation of Anions

Formation of Ionic Compounds Compounds composed of cations and anions are called ionic compounds.

Formation of Ionic Compounds A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance. A formula unit is the lowest whole-number ratio of ions in an ionic compound.

Molecules and Molecular Compounds Atoms held together by sharing electrons are joined by a covalent bond. A molecule is a neutral group of atoms joined together by covalent bonds. A diatomic molecule is a molecule consisting of two atoms of the same type.

Molecules and Molecular Compounds A compound composed of molecules is called a molecular compound.

Molecular Formulas

Single Covalent Bonds Two atoms held together by sharing one pair of electrons are joined by a single covalent bond.

Single Covalent Bonds A pair of valence electrons that is not shared between atoms is called an unshared pair.

Single Covalent Bonds

Double and Triple Covalent Bonds A bond that involves two shared pairs of electrons is a double covalent bond. A bond that involves three shared pairs of electrons is a triple covalent bond.

Binary Ionic Compounds A binary compound is composed of two elements and can be either ionic or molecular. To name any binary ionic compound, place the cation name first, followed by the anion name. SnF 2 = tin(II) fluoride SnS 2 = tin(IV) sulfide Fe 2 O 3 = iron(III) oxide MgO = magnesium oxide NaCl = sodium chloride Al 2 S 3 = aluminum sulfide

Compounds with Polyatomic ions To write formulas for compounds with polyatomic ions, write the symbol for the cation followed by the formula for the polyatomic ion and balance the charges. To name a compound containing a polyatomic ion, state the cation first and then the anion just as you did in naming binary ionic compounds.

Naming Binary Molecular Compounds A prefix in the name of a binary molecular compound tells how many atoms of an element are present in each molecule of the compound.

Naming Binary Molecular Compounds 1. Confirm the compound is binary molecular – a compound composed of two nonmetals. 2. Name the elements in the order listed in the formula. Use prefixes to indicate the number of each kind of atom. 3. The end of the name of the second element is always changed to –ide.

Writing Formulas for Binary Molecular Compounds Use the prefixes in the name to tell you the subscript of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts.