Pure Substances Containing Two Or More Elements in Fixed Proportions

Forming Compounds

Compounds:

pure substances containing two or more elements in fixed proportions

when atoms collide, valence electrons interact to make valence shells stable (like that of nearest noble gas)

There are two types of compounds:

atom may gain electrons
atom may give up electrons

atom may share electronsmolecularcompounds

Ionic Compounds:

usually formed by metal with non-metal

metals lose electrons forming cations
non-metals gain electrons forming anions
combine in a ratio to make a neutral compound
overall charge of the compound must be zero

Ionic Bond:

force of attraction between the oppositely-charged ions

Ex 1:sodium and chlorine

Na + Cl[Na]+[Cl]-

Ex 2:potassium and nitrogen

K + N

[K]+

K[K]+[N]3-

[K]+

Molecular Compounds:

formed by non-metal with non-metal

share electrons to fill valence shell
The nuclei of two different atoms are attracting the same electrons.
combine in a ratio to make stable atoms

Covalent Bond: force of attraction between atoms that share 1, 2, 3 pairs of electrons

Ex 1: methane CH4

H H

Lewis Dot DiagramStructural Diagram

Ex 2: chlorine gas Cl2

Ex 3: What about CO2?

Carbon does not follow the octet rule (8 electrons in outer shell) unless double bonds are formed(two atoms share 4 electrons).

Note: 7 elements exist naturally as diatomic molecules. This means they are always found as: O2 H2 N2 F2 Cl2 Br2 I2

PHYSICAL PROPERTIES OF COMPOUNDS / IONIC
COMPOUND
______with non-metal / MOLECULAR COMPOUND
______with non-metal
Melting point
Conductivity when dissolved in water
Conductivity as molten/liquid
Conductivity as solid

Electrolyte: substance that dissolves in water to produce a solution that conducts electricity.

Name:Date:

SNC 2D worksheet

IONIC AND COVALENT BONDING see p 148 for examples

1. In your notebook, draw Lewis Dot Diagrams showing the formation of ionic compounds from these elements.

a)lithium and oxygend) sodium and flourine

b)beryllium and oxygene) calcium and iodine

c)sodium and sulphur

2. In your notebook, draw Lewis Dot Diagrams showing the formation of molecular compounds from these elements.

a)silicon and oxygend) sulfur and bromine

b)nitrogen and hydrogene) oxygen and fluorine

c)phosphorus and chlorine

3. In your notebook, do textbook questions page 154 #1, 3- 6

4. Define “electrolyte”.

PHYSICAL PROPERTIES Complete using page 151 of text: