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Earth’s Materials - Atoms, Elements, and Compounds. Structure of an Atom. Uniqueness of Elements. An elements is defined by its Atomic Number (number of protons in the nucleus) i.e. Hydrogen’s Atomic Number is 1 Helium’s Atomic Number is 2
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Uniqueness of Elements An elements is defined by its Atomic Number (number of protons in the nucleus) i.e. Hydrogen’s Atomic Number is 1 Helium’s Atomic Number is 2 Mass Number (sum of protons and neutrons) i.e. Hydrogen’s Mass Number is 1 Helium’s Mass Number is 4
Ions - atoms with excess positive or negative charge (gain or loss of electrons from the outermost shell). Cations (positive charge, lose electrons) e + P P e Hydrogen atom Hydrogen ion ( H+) Electron + Anions (negative charge, gain electrons)
Compounds - combination of atoms of one or more elements in a specific ratio. • Examples: N2 - nitrogen gas • H2O - water • CaCO3 – calcite (a mineral) • Ions dissolved in water will combine to form compounds
Types of Bonds • Ionic - transfer of electrons between cations and anions. Moderate strength, Moderate hardness
Types of Bonds • Covalent - electrons are shared between atoms Strong bond/ Hard mineral
Questions -Which of the following are minerals? Explain! • Ice (H2O) • Water (H2O) • Oil (CxHyOz) • Salt (NaCl) • Synthetic (man-made) Diamond (C) It may be helpful to write out the definition of a mineral.
Crystal Form and Habit Cleavage Hardness Luster, Color, Streak Density Taste Feel Magnetism Reaction to Acid Properties of Minerals
Most Common Elements Oxygen Silicon Aluminum Iron Calcium Magnesium Sodium Potassium Percentage by Weight
Oxides O2 Carbonates (CO3)2- Sulfates (SO4)2- Sulfides S Phosphates (PO4)3 Halides (NaCl-salt) Native Elements (Gold) Silicates (SiO4)4- Common Mineral Families Which mineral family would be the most common at the Earth’s surface?
Silicon-Oxygen Tetrahedron • (SiO4)-4 – anion • Building Block of Silicates • Combination of ionic and covalent bonds • Combines with other tetrahedrons and/or cations
Combination of Tetrahedron and cations form minerals i.e. Olivine Mineral Formation
Silicate Structures Si:O 1:2.5 Si:O 1:3 Si:O 1:2.75
Silicon:Oxygen 1:4 1:3 • Silicon content increases with complexity of Structure 1:2.75 1:2.5 1:2
Ferromagnesium (Mafic) Silicates Composed of Iron (Fe) and Magnesium (Mg) Dark in Color Nonferromagnesium (Felsic) Silicates Composed of Potassium (K), Sodium (Na), Calcium (Ca), etc. no Fe and Mg Lower density Light in Color Hornblende Orthoclase Chemical Classification