1. Minerals Chapter 2

2. Matter Section 1

3. Elements and the Periodic Table Everything in the universe is made of matter. Matter is anything that has mass and volume The building blocks of all types of matter are called elements. An element is a substance that cannot be broken down into simpler substances The simplest unit of an element is called an atom Elements are arranged on the periodic table

4. The Periodic Table

5. The periodic table is a model that arranges the elements based on physical and chemical properties A column on the periodic table is called a group. Groups are arranged so that elements within a group have similar chemical properties A row on the periodic table is called a period. A period shows increasing numbers of protons. It also shows how an atoms electrons are arranged.

6. There are 118 known elements Of these, only 8 (oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium) make up 98.7% of earths crust. The other 110 elements make up 1.7% combined New elements are discovered every now and then

7. Again, an atom is the smallest particle of an element that retains the properties of that element Atoms can be broken down into smaller substances called protons, neutrons, and electrons Atoms

8. Diagram of an atom

9. Protons are subatomic particles that reside in the central region of the atom, called the nucleus. They have a positive charge and have a relatively large mass Neutrons are subatomic particles that also reside in the nucleus. The have no charge and roughly the same mass as a proton Together, protons and neutrons account for well over 99% of the mass of an atom

10. Every atom of each element has a unique number of protons, which is called that elements atomic number In general, atoms have the same number of protons as they do electrons. However the number of electrons can be changed. The number of protons cannot change The number of neutrons can also be changed in an atom

11. An electron is a small, negatively charged subatomic particle that has almost no mass. Electrons reside in the area surrounding the nucleus Electrons move very fast around the nucleus Electrons have specific areas they can exist, called energy levels Atoms form bonds with one another because the outer level of electrons interact with one another Electrons

12. Isotopes As we said earlier, the number of protons CANNOT change within atoms of an element However, the number of neutrons can change, creating isotopes - atoms of the same element with differing numbers of neutrons If an atom has too many neutrons, it may become unstable and disintegrate through a process called radioactive decay

13. Isotopes of Carbon

14. Why Atoms Bond Most elements exist in nature combined with other elements A group of two or more combined elements is called a compound Compounds form in order to become more stable The most stable elements will have 8 electrons on their outer energy level There are 3 types of bonds: ionic, covalent, and metallic

15. Ionic Bond An ionic bond forms when one atom loses an electron (forming a positive charge) and another atom gains an electron (forming a negative charge) The positive charge and negative charge attract each other and stick together

16. Ionic Bond

17. Covalent Bonds A covalent bond forms when two atoms share a pair of electrons Covalently bonded compounds are called molecules

18. Covalent bond

19. Metallic Bond A metallic bond is formed when all atoms in a compound share all electrons

20. Metallic Bond

21. Minerals Section 2

22. Minerals A mineral is 1)naturally occurring 2)inorganic 3) solid 4) orderly crystalline structure 5) definite chemical composition

23. How Minerals Form There are four major processes through which minerals form: crystallization from magma, precipitation, changes in pressure and temperature, and formation from hydrothermal solutions

24. Crystallization from Magma Magma is molten rock. It is lava that has not come above the surface. As magma cools, it hardens to form different minerals Different minerals will crystallize at different temperatures as magma cools

25. Precipitation Ever been in a cave? Stalactites and stalagmites were formed through the process of precipitation Precipitation occurs as minerals that are dissolved in water solidify (precipitate) as the water undergoes changes or evaporates

26. Pressure and Temperature Some minerals form when other, existing, minerals undergo large changes in either pressure, temperature, or both This process rearranges the order in which the atoms are arranged, creating a new mineral

27. Hydrothermal Solutions A hydrothermal solution is a very hot water solution of dissolved minerals. When this solution comes in contact with other minerals, a chemical reaction occurs and creates new minerals

28. Mineral Groups There are over 3800 known minerals, with new ones being identified each year However most minerals belong to one of the major groups based on composition: silicates, carbonates, oxides, sulfates and sulfides, halides, native elements

29. Silicates Silicates are a group in which silicon and oxygen combine to form a shape called a tetrahedron A silicon-oxygen tetrahedron is composed of one silicon and four oxygen atoms Silicates are the largest, most common mineral group Quartz - a common silicate

30. A silicon-oxygen tetrahedron

31. Silicate Structures

32. Carbonates Carbonates are the second most common mineral group Carbonates are minerals that contain carbon, oxygen, and one other, metallic, element (like magnesium, or iron)

33. Dolomite - a carbonate that contains carbon, oxygen, and magnesium

34. Oxides An oxide is a mineral that contains oxygen and one or more other elements (usually metals)

35. Rutile, an oxide composed of titanium and oxygen

36. Sulfates and Sulfides Sulfates and sulfides are minerals that contain the element sulfur

37. Fool’s Gold (Iron Pyrite) is a sulfide, FeS 2

38. Halides A halide is a mineral that contains a halogen (halogens are in group VIIA on the periodic table) and one other element An example is table salt (NaCl)

39. Fluorite, an example of a halide with the composition CaF 2

40. Native Elements Native elements are minerals that exist in a relatively pure form Examples include gold, silver, copper, etc.

41. Gold, silver, and copper wire

42. Properties of Minerals Section 3

43. Color Probably one of the easiest properties to identify Color can be a clue to the identity of a mineral, but colors are not unique to specific elements Different elements can be the same color, while the same mineral can be different colors

44. These diamonds have different colors

45. These earrings are made of both purple fluorite and amethyst (a purple variation of quartz). Can you tell which is amethyst and which is fluorite?

46. Streak Streak is the color of a mineral in its powdered form While samples of the same mineral might differ in color, their streak is usually the same Streak is usually a good indicator

47. The streak of two different minerals

48. Luster Luster refers to how light reflects off a minerals surface In other words, how shiny is it?

49. Galena has a metallic luster

50. Diamonds have an adamantine luster

51. Crystal Form The visible shape that indicates the minerals internal arrangement of atoms Crystal form is best when minerals are allowed to form slowly without space restrictions

52. Quartz has a hexagonal crystal structure

53. Fluorite has a cubic structure

54. Hardness Hardness is a measure of how easily a mineral is scratched Mohs hardness scale is set up on a scale of 1 to 10, 1 being the softest and 10 being the hardest Talc is the softest mineral. You can scratch it with your fingernail. Diamond is the hardest mineral A mineral can scratch all other minerals below it on the hardness scale. A mineral cannot scratch other minerals above it (e.g. Diamond can scratch talc, but talc cannot scratch diamond)

55. Mohs hardness scale

56. Cleavage Cleavage is the tendency for a mineral to break along flat, even surfaces

57. Cleavage of mica

58. Fracture If a mineral does not show cleavage when broken, it is said to fracture Fracture is the uneven breakage of a mineral

59. Obsidian shows fracture

60. Density Density shows the ratio of an objects mass to its volume Density = mass/volume Every substance has a unique density that stays the same for every sample of that substance

61. Fools gold and real gold look very similar. The easiest way to tell the difference is to calculate the density. Real gold has a density of 19.3g/cm 3 while fools gold has a density of 5.02g/cm 3

62. When properties are used to identify minerals, it is best to use two or three different properties before identification is made Using Properties to Identify Minerals

63. Unique Properties of Minerals Some minerals have very specific unique properties that identify them Example: talc feels soapy, graphite feels greasy, carbonates react with hydrochloric acid