EPSC201 - Lecture 11 Notes
We established that minerals are chemical com-
pounds that occur naturally. Minerals are expressed
as crystals. Minerals have a set of arranged atomic
arrangement which makes them different from just
random atomic arrangement
• Anion is a negative charged atom
• Cation is a positive charged atom
The size of an ion has a big effect on the geometry of
• Ionic Bonds – the transfer of electrons from
one atom to another, which forms charged ions.
• Covalent Bonds – the bond shares electrons
between the atoms, to fill the outer shell of each atom, making it stable. The bonds are much
stronger then ionic bonds.
Taking halite as an example, the ionic bond created between sodium and chlorine allows for the transfer
of one electron which helps make sodium and chlorine charged ions but also stable. There is an equal
number of sodium and chloride in halite which through ionic bonds, starts building up its molecular struc-
ture by organizing atoms through relative sizes.
Relative Sizes of Ions:
Cations with a high charge are small, if they have
a small charge, they are larger in size.
For anions, there are variation in sizes.
In ionic bonding, we want to pack the anions in
and around the cations, based on the size of both
the cation and anion. We refer to this as ion coordination.
We started talking about diamonds last class; are purely carbon. Every carbon atom is bonding to every
other carbon atom. They are short and strong bonds (homogenous), which results in a super hard struc-
ture. When we say it’s hard, it’s not that we cannot break it with a hammer (we will smash it), what it
means is that it cannot scratch easily. What makes diamond super strong is the fact that the carbons are cova-
lently bonded which makes it super hard.
Diamonds are ONLY formed under high temperature and high pressure
(need depth of at 150-200km). If diamonds were formed on shallow depths,
it would be graphite instead and not diamond. Diamonds reach the surface
of the earth through volcanos; specifically magma liq