Ø 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 ionic compounds  atom may give up electrons

 a t o m may share electrons molecular compounds 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 + - Lewis Dot Diagram Na + Cl [Na] [Cl]

Ex 2: potassium and nitrogen Lewis Dot Diagram K + N

K 3[K]+[N]3-

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 H C H C H H H H

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.

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

PHYSICAL IONIC MOLECULAR PROPERTIES OF COMPOUND COMPOUND COMPOUNDS ______with non- ______with non-metal 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 oxygen d) sodium and flourine b) beryllium and oxygen e) 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 oxygen d) sulfur and bromine b) nitrogen and hydrogen e) oxygen and fluorine c) phosphorus and chlorine

3. In your notebook, do textbook questions page 134 #1-7

4. Define “electrolyte”.

5. Fill out the following table using the resource of your choice. PHYSICAL PROPERTIES PHYSICAL IONIC MOLECULAR PROPERTIES OF COMPOUND COMPOUND COMPOUNDS ______with non- ______with non-metal metal

Melting point

Conductivity when dissolved in water Conductivity as molten/liquid Conductivity as solid