Ch. 3.2 Chemical Composition of Minerals

E. Sci 11 Ch. 3.2 – Chemical Composition of Minerals What is a Mineral?  All matter (rocks, earth’s crust, even you) is made up of elements.  Several things must be true for a material to be called a mineral. A mineral: 1. occurs naturally, 2. is a solid, 3. has a definite chemical composition, 4. has its atoms arranged in an orderly pattern, and 5. is inorganic (not formed by any process involving living organisms).  A substance that fits ALL these criteria is considered a mineral.  Examples of common minerals: quartz, halite (rock salt), mica, gold, and diamond  Some common substances that are NOT minerals:  Water – not a solid  Glass – does no occur naturally and particles are not arranged in an orderly way  Pearl – formed by an oyster  Coal – formed by plant matter, lacks definite composition, and atoms are not arranged in an orderly way  Of all the elements in the Earth’s crust, 8 elements make up a whopping 98.5% of the crust’s total mass. They are:  Oxygen  Calcium  Silicon  Sodium  Aluminum  Potassium  Iron  Magnesium  Oxygen, by mass, makes up 46.6% and 93.8% of its volume.  Silicon, by mass, makes up 27.7% and 0.9% of its volume.  Most minerals are compounds, but some are composed of single elements. These are called native minerals.  Examples: gold, silver, copper, sulphur, and diamond.   How Minerals Form  Atoms in compounds stay together because of bonds. There are 2 types of bonds: 1. Ionic bond  Occurs between metals and non-metals E. Sci 11  Electrons are transferred from metals to non-metals  If an atom gains or loses electrons, it becomes an ion (negatively or positively charged)  Oppositely charged ions attract one another 2. Covalent bond  Occurs between non-metals  Electrons are shared between atoms  Minerals can form in many different ways.  Many minerals form out of molten earth material, or magma. As magma cools, its atoms move closer together and form minerals. The kinds of mineral that form depend on (1) which elements are present, (2) the amounts of those elements, and (3) the rate which the magma cools.  Some minerals form when water containing dissolved ions evaporate.  Minerals can also change into different minerals by heat, pressure, or the chemical action of water.   Naming Covalent Compounds

 Number  Prefix  1  mono-  2  di-  3  tri-  4  tetra-  5  penta-  6  hexa-  7  hepta-  8  octa-  9  nona-  10  deca-  The first non-metal is just given the name as found on the periodic table.  The second non-metal ending is changed to –ide.  Use numerical prefixes to show how many of each non-metal are present.

 Example 1: Si3N4  There are 3 silicon atoms and 4 nitrogen atoms.  It is trisilicon tetranitride

 Example 2: N2O E. Sci 11  There are 2 nitrogen atoms and 1 oxygen atom.  It is dinitrogen monoxide  The only time you do not use a prefix is when there is only one of the first non-metal; mono is never written in front of the first word

 Example 3: CCl4  There are 1 carbon atom and 4 chlorine atoms.  It is carbon tetrachloride.