Properties of Ionic and Covalent Compounds (+ Metallic) Matter and Chemical Bonding: Properties of Ionic and Covalent Compounds (+ Metallic)

Vocabulary Crystal Lattice Polar Non-polar Dipole-dipole force STP Melting Point Boiling Point Solubility Electrical Conductivity Malleable Ductile

Chemical Bonds Chemical Bonds - attractive force that holds atoms or ions together - 3 types ionic, covalent, metallic - determines the structure of compound - structure affects properties - melting/boiling pts, conductivity, solubility, etc.

Ionic Bonds / Ionic Compounds Definition: - bond formed by the attraction between oppositely charged ions cation: positive: lost e-’s anion: negative: gained e-’s - oppositely charged ions attract each other and form an ionic bond ex. Na+ + Cl- = NaCl - electrons are transferred from one atom to another - negative ions attract more positive ions, and soon a network is formed

Networks / Crystal Lattices - repeating pattern of multiple ions ex. NaCl - every Na ion is next to 6 Cl ions - strong attraction between ions creates a rigid framework, or lattice structure: aka: crystals

Covalent Bonds Definition - chemical bond in which two atoms share a pair of valence electrons - can be a single, double, or triple bond single, 2e-’s (-); double, 4e-’s (=); triple, 6e-’s( ) - always formed between nonmetals - mostly low melting/boiling points 2 types of bonds - polar - non polar

Covalent Bonds Non Polar - bonded atoms that share e-’s equally - same atoms bonded ex. Cl – Cl: Cl2 Polar - bonded atoms that do not share e-’s equally - different atoms bonded H ex. H – N – H NH3

Metallic Bonds Definition - a bond formed by the attraction between positively charged metal ion (cation) and the shared electrons that surround it (sea of electrons) ex. Cu

Predicting Bond Type

PROPERTY 1: Melting/Boiling Points The melting point of a compound is the temperature at which it changes from a solid to a liquid at STP. The boiling point of a compound is the temperature at which it changes from a liquid to a gas at STP.

PROPERTY 1: Melting/Boiling Points A low melting or boiling point means small amounts of kinetic energy are enough for a particle to break away from its neighbours. the forces between the particles are weak. A very high melting or boiling point means the particles must have a very large amount of kinetic energy to break away  the forces between the particles are strong

Consider the following: COMPOUND BOILING POINT ( °C) ethanol +78.3 ammonia +33.3 cesium bromide +1300 hydrogen gas -253 magnesium oxide +3600 methane -161 nitrogen gas -196 sodium chloride +1465 water +100 Sort the compounds according to their boiling points. What do you notice?

High Melting and Boiling Points = IONIC COMPOUNDS This means that the attractive electrostatic forces between oppositely charged particles create very strong bonds. The crystal lattice arrangement of ionic compounds means that multiple ions are involved in this interaction simultaneously, which results in a great force.

Medium Melting and Boiling Points = COVALENT COMPOUNDS with POLARITY The medium strength of the polar covalent bonds is a result of the dipole-dipole force. This is the attractive force between the positive end of one molecule and the negative end of another molecule.

Low Melting and Boiling Points = NON-POLAR COVALENT COMPOUNDS Although non-polar molecules have no distinct separation of charge, it is still possible for the positive nuclei of atoms in one molecule to attract the electrons of a neighbouring molecule.  These forces are very weak!

PROPERTY 2: Water solubility The partially positive H in water is attracted to negative ions of an ionic compound or the partially negative atom of a polar compound. The partially negative O in water is attracted to the positive ions of an ionic compound or the partially positive atom of a polar compound. IONIC AND POLAR COVALENT COMPOUNDS ARE WATER SOLUBLE. NON-POLAR COVALENT COMPOUNDS ARE NOT WATER SOLUBLE.

PROPERTY 3: Electrical Conductivity Electrical conductivity is the ability of a substance to allow an electric current to pass. A substance is conductive if charges can move independently of one another. This is only possible for ionic compounds in the liquid state or dissolved in water. For this reason they are called electrolytes Since in covalent compounds , electrons do not leave an atom completely these compounds do not conduct electricity when in liquid state. They are called non-electrolytes.