Chemical Bonds

Electrical in nature- responsible for most mineral properties1) Ionic Na: low 1st IP e- Na+ (Ne config)

Cl: high e-neg takes e- & = Cl- (Ar config)Now they have opposite charges & attract bond

Poor electrical conductors.Bonding is strong (high melting point)disrupted by polarized solvents (water)Bonding is non-directional, symmetry of atomic arrangement is high

Chemical Bonds2) Covalent

Sharing electrons such as in Si-O, S-O, P-O, C-O and C-C

Double bonds when 2 orbitals shared, e.g.

V=O, U=O, C=O

Triple bonds when 3 orbitals shared;

e.g. N=N

Chemical BondsHybrid orbitals

Carbon: | | | 1s 2s 2p 1s 2(sp3)

C-C-C angle = 109o 28’

Fig 8-8 of Bloss, Crystallography and Crystal Chemistry. © MSA

Chemical BondsHybrid orbitals

Alternatively:

Carbon: | | | | 1s 2s 2p 1s 2(sp2) 2p

The 3 2(sp2) orbitals are coplanar & 120o apart

Chemical Bonds

Fig 8-8 of Bloss, Crystallography and Crystal Chemistry. © MSA

Graphite structure

Covalent structures

diamond 4 x 2(sp)3 Hybrids Graphite 3 x 2(sp2) Hybrids

Chemical properties Chemical properties of minerals of minerals containing only one containing only one type of bonds listed type of bonds listed in Table 3.9 of text in Table 3.9 of text bookbook

3) Metallic Bonding

Atoms are closely packed in metal structures.

"touching" nearest neighbors

A high density of valence e- around any given atom & also a high density of neighbor atoms around the loose valence e-

The effect is to show such a general attraction for these e- that they become free to maintain an electrical neutrality:

Electron gas = good conductivityFurther good ductility

Chemical Bonds

Chemical Bonds4) Van der Waals Bonds

Weakest bond

Usually between neutral molecules (even large ones like graphite sheets)

Produced by polar or partial polar covalent bonds or polar atoms

Weakness of the bond is apparent in graphite cleavage

Condensed ClCondensed Cl22

cov VdWcov VdW

Hydrogen bonds

Stronger bond that VAN DER WAALS bond

Occurs between polar groups of atoms in liquids and solids

e.g. H2O

-

+

-- -

- -

-

+

+++

++

Water and Ice