Chapter 5: Atoms to Minerals

1. Chapter 5: Atoms to Minerals

2. Chapter 5.1

3. Matter and Atoms

4. Matter • Anything that has mass (amount of material) and volume (amount of space an object takes up) • Ordinary matter is composed of elements (a substance that cannot be broken into a simpler substance by ordinary chemical means) • 200 years ago, John Dalton stated that “each element is made up of tiny particles, all alike, called atoms” • Dalton describes an atom as the smallest part of an element that has all the elements properties.

5. Structure of an atom • In its normal state, a neutral atom as an equal number of electrons and protons • Atomic # tells how many protons are in the nucleus and is equal to the # of electrons in the electron cloud • The nucleus has 99.9% of the atoms mass • Energy levels of electrons represents how many electrons each level can hold 2, 8, 18, 32, 21, 9, and 2

6. Classifying Atoms • Periodic table of elements p. 698 • Rows represent the increasing number of protons • Vertical columns group these elements that have similar chemical properties • Mass #; sum of protons and neutrons

7. Isotope – an atom with a different # of neutrons • Potassium • Atomic Number • 19 • Symbol • K • Atomic Mass • 39.10 amu • K has 19 protons (atomic number) • 20 neutrons (atomic mass – atomic # [39 – 19]) • 19 electrons; always equals the of protons

8. Bonding of Atoms • Most substances on earth are not pure they are compounds – contains atoms of 2 or more elements. • For a substance to be stable it likes its last electron level to be filled so they fill it by losing or gaining electrons • Covalent Bonds – share electrons

9. Ionic Bonds – when atoms loose or gain an electron they became charged. • Gained; [-] Charge • Lost; [+] Charge • The opposite charge will then attract • Ion – a charged atom • A metal looses electrons easily to form positive ions. Therefore they can not join with other metals. • Nonmetals gain electrons easily to form negative ions. This makes them want to bond to the positive metals.

10. Metallic Bonds – The bonds that form between metals cause the electrons to move around all the positive ions.

11. Compounds and Mixtures • Compounds can have properties entirely unlike those of the elements of which it is made. • Salt NaCl Sodium and Chlorine are both poisonous to humans when separated • Compounds can only be separated by chemical means. • Mixtures – elements keep their own properties • Salt water – water can be separated by boiling

12. Sodium Metal + Chlorine Gas Halite (Table Salt) =

13. Chapter 5.2

14. Composition and Structure of Minerals

15. What is a mineral? • A mineral must be • Naturally occurring • Solid • Definite chemical composition • Orderly arrangement of atoms • Inorganic (never alive) • Most minerals are compounds • Quartz SiO2; Silicon and Oxygen • Native elements – minerals with a single element • Gold (Au), silver (Ag), copper (Cu), Sulfur (S), diamond (C) • Rock – different types of minerals and native elements mixed together

16. Diamond (C) Silver (Ag) Copper (Cu) Gold (Au) Sulfur (S) Native Elements

17. How minerals form • Many minerals form from molten rock in which the atoms can move freely. Once it begins to cool the ions move closer together to form chemical bonds • Many different minerals will form. The composition of the magma will control what type form. • The slower the magma cools the larger the grains. • Can also form from evaporating water – salt • New minerals will form when existing minerals are exposed to more heat and pressure.

18. Structure of Minerals • Crystal Structures • The orderly arrangement of atoms in a mineral often seen as the minerals shape • Salt p. 98 • Crystal is a regular geometrical solid with smooth surfaces called crystal faces. • Each mineral has its own crystal form • There are six basic shapes p. 99

19. Silicates – minerals that are compounds including silicon and oxygen • They also may contain a metal atom • Silica tetrahedron – 4 oxygen surrounding 1 silicon

20. Crystal Structures and Physical Properties • Cleavage – tendency to split along definite planes • Hardness – resistance to scratch. Sometimes the same element can have different hardness based on its internal structure • Diamond – pure carbon very hard • Graphite – pure carbon very soft

21. Chapter 5.3

22. Identifying Minerals • Mineralogy – study of minerals and their properties

23. Rock Forming Minerals

24. Identifying Minerals by Inspection • Very rarely are minerals Id. by one property • Types of Properties • Color – easily observed but, least useful • Luster – how a mineral reflects light • 2 basic types • Metallic • Nonmetallic • Crystal shape

25. Streak – color of a powdered mineral • Metallic minerals streak is at least as dark as a specimen • Nonmetallic – colorless or white • Cleavage – minerals splits along flat surfaces

26. Fracture – breaks in directions other than cleavage planes • Conchoidial - shell like fracture • Splintery – jagged surface • Uneven – rough surface • Hardness – resistance to scratch • Mesh’s hardness scale 1- 10

27. Chapter 5.4

28. Mineral Groups

29. Major Silicates • 90% of the minerals in earth’s crust are silicates • Quartz – used in watch movements, prisms, heart lamps, lenses, glass and paints. Crystals are considered semiprecious • Feldspars – used aluminum atoms in place of some of the silicon which become balanced by other metals. It is used in glass and ceramics • Micas (biotite and muscovite) used as electronic insulators, paints, plastics, rubber and roofing.

30. Biotite Quartz Feldspar Silicates

31. Ferromagnesium Silicates • Olivine – gem quality is known as peridote • Kaolinite – is pure white, a clay compound used in ceramics, paint and fiberglass also known as china clay

32. Carbonates – negative carbonate ions bonded to positive metal ions which are used construction. Calcite and Dolomite give us rock like limestone and marble.

33. Oxides – Iron bonded with oxygen of sulfur (sulfide) • Hematite – iron oxide used to make steel medicine, cosmetics, plastics and paints

34. Hematite Iron Oxide Fe O 2 3