Part II. How to build a planet (continued) Atoms, Compounds, and minerals:

Earth is made of minerals.

1. What is a mineral?

• Physical properties of minerals.
  (Crystal structure and composition are the 2 parameters that determine what mineral forms and control physical properties.)
  • Luster.
  • Cleavage.
  • Crystal faces
  • Hardness.
  • Color
  • Specific gravity (density).
  • Special properties (magnetism, taste, reaction with acid)

How to build a crystal.

1. Composition.

a. Atom: the smallest unit of an element. It is hard to imagine, but an individual atom of an element would exhibit the properties of the element.

i. Examples: hydrogen, carbon, iron, aluminum, sulfur, uranium.

ii. More than 106 elements known.

iii. 92 occur naturally on Earth.

iv. Structure:

• Nucleus (protons and neutrons)
  • most of the atom's mass.
  • The number of PROTONS identify/define the element.
  • The number of neutrons determines the isotope of the element.
• Electrons:
  • Found in a cloud around the nucleus.
  • Have almost no mass.
  • The number and their orbital energy determine the chemical characteristics of the atom / element.

Check out this article in National Geographic that shows a recently discovered cave in Mexico that has gypsum crystals up to 36 feet long! Here are some more photos from this cave.

Diamonds are the stable form of carbon in the Earth's mantle. Here is a story about how the composition of diamonds is being used to understand ancient plate movements.

Week 3: Study Questions

Atoms, Compounds, and minerals:

Practice questions:

1. Which of the following determines (or identifies) an element?

• The number of electrons.
• The number of protons and neutrons.
• The number of neutrons.
• The chemical bonds.
• The number of protons.

2. The following are examples of minerals EXCEPT:

• Halite.
• Iron.
• Diamond.
• Gold.
• Coal.

3. Sulfur is a major component of which mineral listed below?

• Quartz.
• Amphibole.
• Micas.
• Diamond.
• Galena.

Answers:

Part II. Atoms, Compounds, and Minerals

1. = The number of protons.
2. = coal.
3. = galena.

In addition to your lecture notes and textbook check out: this web page that has everything you ever wanted to know about your favorite mineral.