bonding

Ionic bonding

-electrons are transferred from one atom to another

-the resulting ions ae held together in a crystal lattice by strong electrostatic attraction between opp charged ions

Positive ions

-cations, electrons removed

Negative ions

-anions

-larger than original- electron repulsion in outer shell

-energy released as the nucleus pulls in an electron

-this energy is electron affinity

Electron affinity

The energy change when one mole of gaseous atoms acquires one mole of electrons to form one mole of gaseous negative ions. The greater the effective nucleuar charge, the easier an electron is pulled in

Strength of ionic compounds

-brittle

-if you move a layer of ions you get ions of the same charge net to each other, layers repel each ther and crystal breaks up

How does ion size affect ionic strength

For ions of the same charge, the smaller the size the more energy required to break the bond because the lattice is more tightly packed

Ionic radius

Measure of size of ion

Increase with increase negative charge, decrease with increasing positive charge

Neg ions and ionic radius

Formed by gaining electrons so increases ionic radius

Pos ions and ionic radius

Losing elections so decreases ionic radius

Isoelectronic

Same electron configuration

Ionic radius decreases as number of protons increases as the electrons are attracted more strongly

Covalent bonding- octet

-some dont achieve an octet- not enough electrons

-others only share some as if thy share all they’ll exceed octet

-from 3rd period onwards, they can exceed octet and are nit restricted to 8 in outer shell

Orbital theory

A covalent bond is an overlap of orbitals which can contain a pair of electrons

-the greater thee overlap the stronger the bond

Dative covalent bonding

Both electrons of the shared pair are provided by one species

NH4+

Empty 1s orbital of H+ overlaps with orbital pf N which contains lone pair

Al2cl6

Lewis base

A lone pair donor

Lewis acid

A lone pair acceptor

Silica

High melting point- many bonds

Strong- each silicon atom joined o 4 oxygens

-non conductor