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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