1. Chapter 2.1

2.  Why do we care about chemistry in Earth Science?  The earth is made up of rocks and minerals.  Rocks and minerals are made of elements.  An element is a substance that cannot be broken down into a simpler substance by chemical or physical means.

3.  Elements are made up of atoms.  An atom is the smallest particle of matter that contains the characteristics of an element.  The center of an atom is called the nucleus.  The nucleus is made up of particles called protons and neutrons.  Particles called electrons surround the nucleus.

4.  Protons are positively charged and weigh approximately 1 atomic mass unit or (amu).  Neutrons have no charge and weigh approximately 1 atomic mass unit or (amu).  Electrons are negatively charged but they have hardly any mass at all.

6.  Atoms of any element always have a specific number of protons that doesn’t change.  The number of neutrons however, can vary.  An atom that has the same number of protons but a different number of neutrons is referred to as an isotope.

7.  A compound is a substance that consists of two or more elements that are chemically combined in specific proportions.

8.  Atoms have energy levels (sometimes called shells) that contain electrons.  The first energy level can hold 2 electrons.  The outer energy levels hold 8 electrons.  If an atom’s outer energy levels are not full, they will chemically combine or react with other atoms to make their shells full.  After the reaction is complete, the atoms are combined to form compounds.

9.  When elements chemically combine to form a compound it is called bonding.  Ionic bonds form between positive and negative ions, when one ion gives up an electron and another ion receives an electron.  An ion is an atom that has an electrical charge because of a gain or loss of one or more electrons.

10.  Sodium (Na + ) and Chlorine (Cl - ) are both ions that form an ionic bond to make Sodium Chloride (NaCl).  Sodium has one electron in its outer shell that it loses to become positively charged. Chlorine has seven electrons so it gains an electron from sodium to become negatively charged.

11.  When atoms do not give up or receive atoms, another way to chemically combine is to share electrons.  When atoms share rather than give or receive electrons it is referred to as a covalent bond.  Water is a good example of a covalent bond.

12.  And lastly, another common type of chemical bond that occurs with earth’s rocks and minerals are metallic bonds.  Metallic bonds are similar to covalent bonds in that the electrons are shared, but unlike the electrons in a covalent bond, electrons in a metallic bond can move freely through a metal.  This gives metals their unusual properties like having the ability to conduct electricity, and being malleable and ductile.