Chemical Bonding Ionic and Covalent Bonds

What is a chemical bond? An attractive force that holds two atoms together Can form by – The attraction of positive ion to a negative ion or – The attraction of the positive nucleus of one atom and the negative electrons of another atom

Bond the interaction between two or more atoms that allows them to form a substance different from the independent atoms. involves the outer (valence) electrons of the atoms. These electrons are – transferred from one atom to another or shared between them.

Bonding Chemical compounds are formed by the joining of two or more atoms. A stable compound occurs when the total energy of the combination has lower energy than the separated atoms. The bound state implies a net attractive force between the atoms... a chemical bond.

Chemical Bonds In chemical bonds, atoms can either transfer or share their valence electrons.

When atoms transfer electrons Ionic Bonds When one or more atoms lose electrons and other atoms gain them in order to produce a noble gas electron configuration, the bond is called an ionic bond.

Ionic Bonding metallic atoms tend to lose electrons When they do so, they become positively charged ions which are called cations. Nonmetallic atoms tend to gain electrons to become negatively charged ions which are called anions. These oppositely charged cations and anions are attracted to one another because of their opposite charges. That attraction is called an ionic bond. We often refer to the charge on the ion as the oxidation state of that element.

Ionic bonding Lewis dot

Ionic Solids Ionic solids are solids composed of ionic particles (ions). These ions are held together in a regular array by ionic bonding. Ionic bonding results from attractive interactions from oppositely charged ions. In a typical ionic solid, positively charged ions are surrounded by negatively charged ions and vice-versa. The close distance between these oppositely charged particles results in very strong attractive forces. The alternating pattern of positive and negative ions continues in three dimensions. The regular repeating pattern is analogous to the tiles on a floor or bricks on a wall. called the crystal lattice.

Ionic Compounds Crystalline solids (made of ions) High melting and boiling points Conduct electricity when melted or dissolved in water Many are soluble in water but not in non- polar liquid

Common Ionic Compounds – NaCl - sodium chloride - table salt – KCl - potassium chloride - present in "light" salt (mixed with NaCl) – CaCl 2 - calcium chloride - driveway salt – NaOH - sodium hydroxide - found in some surface cleaners as well as oven and drain cleaners – CaCO 3 - calcium carbonate - found in calcium supplements – NH 4 NO 3 - ammonium nitrate - found in some fertilizers

Covalent (Molecular) Compounds Gases, liquids, or solids (made of molecules) Low melting and boiling points Poor electrical conductors in all phases Many soluble in non- polar liquids but not in water

Covalent Network Solids Covalent because combinations of nonmetals Interconnected very hard and brittle Insoluble Extreme melting and boiling points Diamond

Covalent Bonds involve the sharing of a pair of valence electrons by two atoms Such bonds lead to stable molecules if they share electrons in such a way as to create a noble gas configuration for each atom

Covalent bonding Lewis Dot