Ncea level 2 - Structure and Bonding

ionic solids

have high melting point, strong intermolecular forces, can only conduct electricity in liquid state.

Molecular solids

have low melting points, weak inter-molecular forces (Van der Waals) but strong intra-molecular forces, can only conduct electricity in liquid state.

Metallic solids

have very high melting/ boiling points, strong inter-molecular forces between particles, always conducts electricity.

Covalent network

very high melting points, strong inter molecular forces, does not conduct electricity except graphite

Graphite

can conduct electricity due to the vast electron delocalization within the carbon layers these valence electrons are free to move, so are able to conduct electricity. However, the electricity is primarily conducted within the plane of the layers.

Graphite

Is soft unlike it's allotrope diamond because of it's structure, although it has strong intramolecular forces in the layers of carbon, there is only weak forces between the layers this allows the layers of carbon to slide over each other.

Lewis diagram

in drawing this all the valence electrons are drawn, the first written atom in the formula is usually the middle atom.

Inter-molecular forces

are weak between molecule forces e.g H20-H20 can easily be overcome.

Intra-molecular forces

are strong within forces e.g H-20 it takes a lot more energy to overcome these bonds

Ionic bond

The bonding electrons spend almost all their time with the more electronegative element (electrons are transferred)

Electronegativity

describes how strongly an atom of an element can attract or hold onto another atoms electrons.. (0.5-4.0)

Pure covalent Bond

The electronegativities are the same (same element) or when the difference of electronegativities is small, the electrons are shared evenly between the 2 atoms.

Electrical dipole (polar bond)

When one atom is more strongly attractive but the other is still somewhat attractive- electrons are shared between the 2 atoms but spend most of their time with the more attractive atom, since the electrons are unequally distributed- each atom ends up with a slight electrostatic charge.