Structure, Bonding and Properties (copy)

Atoms

Ionic Bonding

Ionic Bonding

Ionic bonding occurs between a metal and a non-metal. Metals lose electrons to become positively charged.

Ionic compounds form structures called giant lattices.

E.G. Sodium Chloride

Na has 1 electron in its outer shell Cl has 7 electrons in its outer shell. When an atom loses/gains an electron it becomes an ion (charged atom)

Na loses one electron, and Cl gains one electron

Na forms a Na + ion

Cl forms a Cl- ion

NaCl

Properties

Ionic compounds are solid at room temperature because they are arranged in a giant lattice structure that is held together with strong electrostatic attraction. It takes a lot of energy to break the bonds so they have a high melting point ( are solids)

Ionic compounds are brittle (they shatter break when they are hit)

Solid ionic compounds cannot conduct electricity unless they are molten or dissolved in water

Covalent Bonding

Covalent bonding occurs between non-metals only, the atoms share a pair of electrons so they can both have a full outer shell. Simple covalent molecules have a low boiling point this is because weak intermolecular forces hold together the molecules and they don’t require much energy to break. The covalent bonds that hold the atoms together are strong. They do not conduct electricity because they do not have any delocalized electrons.

Dot and cross diagrams are useful to show the bonding in simple molecules. However, it only shows the electrons on the outer shell

Stick diagrams are easy to draw however they don’t show any electrons or the shape of the atoms

3D diagrams are difficult to draw and don’t show electrons however they do show the shape well

Giant covalent structures

Diamond

Each carbon atom is bonded to four other carbon atoms making a diamond very hard. Large amounts of energy are needed to break the strong covalent bonds therefore it has a high melting point

Silicon dioxide

Silicon dioxide has a similar structure to diamond - there are four bonds for each silicon atom and 2 bonds for each oxygen has a high melting and boiling point

Graphite

Graphite is made up of layers of carbon arranged in hexagons. Each carbon is bonded to three other carbons and has a delocalized electron that is able to move around and carry a charge. The layers of carbon can slide over each other easily as they are held together by weak intermolecular forces, this gives it a slippery texture.