Topic 2: Bonding & Structure 1️⃣&2️⃣

• High melting temps • Good electrical conductivity • Good thermal conductivity • Malleability • Ductility

The electrostatic force of attraction between the nuclei of metal cations and delocalised electrons

The number of delocalised electrons per cation plays a role in determining the melting temp : Group 1 have lower melting points than group 2 Size of cation also affects melting temp : Smaller the cation the smaller the atomic radii = increasing in melting temp

When a potential difference is applied across the ends of a metal the delocalised electrons will be attracted to and move towards the positive terminal of the cell - movement of electrical charge constitutes as an electric current

2 factors: Delocalised electrons are free moving - can pass KE along the metal Cations are closely packed - can pass KE from one cation to another

When stress is applied to a metal the layers of cations may slide over one another Since the delocalised are free moving, they move with the cations and prevent strong forces of repulsion forming between cations in different layers

Solid materials consisting of a regular array of oppositely charged ions extending throughout a giant lattice network

Size of the ions : smaller= stronger Charge on ions : larger = stronger

High melting temperatures Brittleness Poor electrical conductivity when solid but good when molten Often soluble in water

Many ions in a lattice and the combined electrostatic forces of attraction among all of the ions is large so a large amount of energy is required to overcome those forces sufficiently for the ions to break free from the lattice and be able to slide past eachother

If stress is applied to a crystal if an ionic solid then the layers of ions may slide over eachother Ions of the same charge are now side by side and repel one another so the crystals break apart

No delocalised electrons & ions are not free to move under the influence of an applied potential difference Molten ionic compounds will conduct since the ions are now mobile and will migrate to the electrodes of the opposite charge

• Energy required to break apart the lattice structure and separate the ions can in some instances be supplied by the hydration of the separated ions produced. • Both positive and negative ions are attracted to water molecules because of the polarity that water molecules possess.

Ability if an ionic compound to conduct electricity and undergo electrolysis when either molten or in aqueous solution - positive ions will migrate towards the negative electrode where they gain electrons and become atoms - negative ions will migrate to wards the positive electrode where they lose electrons and become molecules

The strong electrostatic attraction between the nuclei of two atoms and the bonding pair of electrons

A sigma bond

A sigma bond

A pi bond - can’t be formed until an sigma bond has been formed which means pi bonds only exist between atoms that are joined by double/triple bonding

The pi bond in ethene is weaker than the sigma bond

The distance between nuclei of the two atoms that are covalently bonded together

The shorter the bond length the greater the bond strength. This is a result of an increase in electrostatic attraction between the 2 nuclei and the electrons in the overlapping atomic orbitals

The ability of an atom to attract a bonding pair of electrons

Decreased down the periodic table Increases from left to right along the periodic table

• If two atoms of the same element are bonded together by the overlap of atomic orbitals, the distribution of electron density will be symmetrical because their electronegativities are identical • However if the two bonded atoms have different electronegativities the distribution won’t be symmetrical - the end of the molecule with the higher electron density will have a slightly negative charge