Understanding the Properties of Compounds Chapter 6

6.1 Ionic Compound Where one or more electrons of one atom are transferred to another atom Linked by ionic bond which is formed by the attraction between oppositely charged ions Usually composed of a metal and one or more non metals

Properties of Ionic Compounds Mostly exist in crystal lattice arrangement (regular repeating pattern of ions) Often solid with high melting points Often soluble in water Often conduct electricity when melted

Examples 1. Sodium Chloride (NaCl) Also known as salt used to flavour food Also used to de-ice roads in winter (lowers the freezing point of water) 2. Sodium Fluoride (NaF) Found in toothpaste used to strengthen tooth enamel

Examples 3. Calcium Carbonate (CaCO3) Also known as chalk 4. Magnesium Carbonate (MgCO3) Also known as scum (hard, white scales on bath tub, water kettle)

How Ions Dissolve Water separates the negative and positive ions from each other and break the ionic bonds Each ion is attracted to the water molecules and is able to move about Water molecules have partial negative and positive charges that allow them to attract other charged particles

How Ions Form Solids Each ion is strongly attracted to the ions around it Solid state is a result of large attractive forces Also result to high melting points

How Ions Conduct Ions have to be unlocked from their crystal structure (meaning: dissolved) Ions in liquid state are free to move around and can conduct well Example: Pure water is a poor conductor but tap water with dissolved minerals is a good conductor.

6.2 Molecular Compound Forms when atoms share a pair of electrons Bond formed between these atoms is called covalent bond Usually between non metal and non metal

Molecules with Electron Sharing

Ball and Stick Model

Properties of Molecular Compounds Exist as solids, liquids or gases Many are not soluble in water Often do not conduct electricity Have a weaker attraction between molecules (compared to ionic compounds) Have low melting and boiling points

Examples 1. Dihydrogen monoxide (H2O or water) Considered the universal solvent 2. Carbon Dioxide (CO2) Involved in respiration and photosynthesis A greenhouse gas

Examples 3. Carbon Monoxide (CO) A poisonous gas that is colourless and odourless 4. Hydrogen Peroxide (H2O2) Used as a disinfectant

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