Octet rule Chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet (8) of electrons in it’s highest energy level.

Electron dot notation Electron dot notation is a configuration notation that only shows the valence electrons of an atom, using dots and the element symbol (on board)

Lewis Structure Lewis structures use element symbols, dots, and dashes to represent atoms, valence electrons and bonds On board

Multiple covalent bonds A dash between element symbols represents and bond a single dash is a single bond, two dashes in a double bond, three dashes is a triple bond On board

An ionic formula indicates the relative numbers of ions of each kind in a chemical compound by using atomic symbols and numerical subscripts. NaCl MgCl2 Al2O3

Chapter 8 Covalent bonding Molecular compounds

A chemical formula indicates the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts.

A molecule is a neutral group of atoms that are held together by a covalent bond A molecular compound is a chemical compound whose simplest units are molecules

A molecular formula show the types and numbers of atoms combined in a single molecule of a molecular compound. A chemical formula indicates the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts.

electronegativity Is the ability of an element’s atom to attract electrons. We can use the difference in electronegativity to predict how atoms will bond together, ionic bonds or covalent (also called molecular) bonds.

Two H atoms bond with one O atom to form H2O if we look at the difference in electronegativity, we see that H is 2.1 and O is 3.5. 3.5 – 2.1 = 1.4 so the bond between H and O is a polar covalent bond. By definition a neutral group of atoms held together by covalent bonds is a molecule. So, the H2O particle is a molecule H2O is a molecule which makes H2O a molecular compound and a molecular formula. But H2O is also a chemical formula because we use atomic symbols and subscripts to describe it.

Formation of a covalent bond

Bond energy is the energy required to break a chemical bond and form neutral isolated atoms.

Diatomic molecule A diatomic molecule is a molecule containing only two atoms of the same element. There are seven elements that exist as diatomic molecules in nature Ex: H2 N2 O2 F2 Cl2 I2 Br2

Resonance Structures

Resonance Structures Resonance structures refers to bonding in molecules or ions that cannot be correctly represented by a single Lewis structure

Resonance Structures But some structures have more than one Lewis Structure; O3 - Ozone O O O or O O O

Resonance Structures