C2 Chemical Bonding

C2 Chemical Bonding

“Welcome, folks, to the Atoms Administration.”

 

Ions are charged particles that have an excess or deficiency of electrons. Elements form ions by gaining or losing electrons in attempt to achieve a full outer shell. Metals form positively charged ions, cations and non metals negatively charged ions, anions.

 

Ionic bonding is the type of bonding between a metal and a non-metal including formation of ions and electrostatic attraction between them. They occur in lattice structure, a regular arrangement of alternating positive and negative ions, such as sodium chloride table salt. It is very strong. An ionic reaction is a redox reaction in that one compound gains electron and the other loses electrons.

 

Molecules and covalent bonds.

Non-metallic elements form covalent bonds with each other, in which electron is shared between atoms.

 

	Ionic	Covalent
Melting point	high	low
Volatility	higher	lower
Solubility	Generally soluble to form solutions that conducts electricity	Insoluble in water and solutions in other solvents will not conduct electricity
Electrical conductivity	Conducts when molten / liquid, when there is a sea of delocalized electrons	never
Structure	Solid: positive negative ions attracts together to form regular 3D ionic lattice. Strong, regular structure is produced, crystalline solid that has a high melting point. Liquid: contains free-moving ions that conducts electricity.	Solid: Atoms bond into molecules held together by weak forces of attraction, hence low melting point. Liquid: has free moving molecules and hence does not conduct electricity.

 

Giant structures

 

Giant covalent structures are massive networks of covalently bonded molecules that has a regular repeating pattern in which many lattice structures occur. Examples are diamonds and graphite, which are allotropes of carbon. Diamonds have 4 carbon bonds while graphite has 3.

 

Diamond is very hard and a hexagonal structure is created around each carbon atom. They have very strong covalent bonds.

 

Graphite occurs in layers and in each layer, each atom is bonded to 3 bonds and forms a hexagonal shape. There is a 1 free electron from each carbon atom. The bonds between the layers are not strong covalent bonds but weak intermolecular forces due to free electrons. Hence, graphite is used in pencils and lubricants since layers can slide off each other and it rubs off each other. Layers of graphite come onto the paper.

 

Silicon dioxide also makes hexagons, each silicon is bonded to 4 oxygen atoms covalently. Each oxygen atom is bonded to 2 silicon atoms. It is a giant covalent structure and it has strong bonds. It is a lattice structure that continues in 3D with regular patterns.

 

Structure of a substance determines its physical properties.

 

	Diamond	Graphite
Hardness	The hardest known substance	Soft and slippery
Melting point	>3500C
Appearance	Transparent, shiny and sparkly	Opaque, dull, black/silver
Conductivity	Does not conduct electricity	Conductor
Uses	Jewellery, cutting, drill heads	Lead in pencils, lubricant

 

Metallic bonding

 

Metals conduct electricity because there is a lattice of positive metal ions in a sea of delocalized electrons in a tightly packed regular structure, in which electricity can flow freely. Ions are held together by attraction to bonding electrons.

 

Malleability is due to non-directional metallic bonds since bonding electrons are free to move, making them easy to bend.