Physical Geology

Chapter 4

Matter

• Anything that has mass and volume

• Elements = simplest stable form of matter

• Made of atoms

• Compounds = chemically combined elements

• Made of molecules

• Elements:atoms::compounds:molecules

98% of crust is 8 elements and their compounds

Atomic Structure

• Small electrons in cloud (- charge)

• Much larger protons in nucleus (+ charge)

• Slightly larger neutrons

in nucleus (0 charge)• Every element unique

• Common units of mass, such as grams, are much too large to conveniently describe the mass of an atomic nucleus or any of its constituent parts. To solve this problem a new unit was defined: the atomic mass unit (amu). The atomic mass unit is a relative unit defined arbitrarily by assigning a mass of 12 amu to the neutral atom carbon-12, the common isotope of carbon. One atomic mass unit equals 1.66 X 10-24 grams. Employing this value, the masses of the fundamental particles of an atom have been determined to be:

• (1) Proton mass: 1.00727 amu. • (2) Neutron mass: 1.00867 amu. • (3) Electron mass: 0.00055 amu.

= atomic number

= atomic mass

• Forms of the same element

• Differ in # of neutrons

• Same atomic number but different atomic mass (heavier)

• Similar behavior with some different properties

• Leads to average atomic mass

• H = 1.00794 amu

Ions

Valence electrons create behaviors/properties and establish

periodic groups on table

• Metals have 1-3 valence electrons and lose them easily

• Non-metals have 4-7 electrons and tend to gather more

Mendeleev’s Table

2 and 8 electrons create unreactive state (Happy) Is this important?

How do they become “happy”?Chemical bonding!

Ionic bond – giving/taking e-

Covalent bond – sharing e-

Polar covalent molecule

+

_

Mixtures

• Unlike a compound, the components are not chemically combined, just physically combined

• Heterogenous – not equally mixed

• Homogenous – “solution” and equally mixed