Atoms to Minerals CH 5.1

Transcription

1 Atoms to Minerals CH 5.1

2 Objectives Identify the characteristics of matter Compare the particles that make up atoms of elements Describe the three types of chemical bonds Identify the characteristics of minerals Explain how minerals form List the physical characteristics of minerals that are influenced by their crystalline structure Identify rock-forming minerals by inspection, using physical properties such as color, luster and crystal shape Identify rock-forming minerals using simple tests that identify both physical and chemical properties, for example streak, specific gravity, and the acid test Describe the properties of the most common minerals, silicates and carbonates Describe tests used to identify mineral groups

3 Matter & Atoms Matter: anything that has mass + volume Mass-measure of amount of material in an object Not same as weight! Weight-measurement of force of gravity acting on an object or substance. Volume-amount of space taken up by an object or substance

4 Matter is Composed of Elements elements: a substance that cannot be broken into simpler substances by ordinary chemical means Made of tiny particles atoms (smallest part of element that has all the element s properties composed of charged particles (electron) high speeds about nucleus Nucleus contains protons (+) & neutrons (⁰) Neutral state-same # + (protons) and - (electrons) Atomic number-number of protons in nucleus of element (equal to # electrons)

5 Common Atoms Hydrogen- simplest + lightest of all atoms Most common form has 1 proton + no neutron Helium Next lightest element 2 protons, 2 neutrons, 2 electrons Carbon * very common & special Most common form-6 protons, 6 neutrons, 6 electrons

6 Energy Levels Atoms w/ > 2 electrons, e-cloud is divided into energy levels. Each level can only hold a certain number of electrons For our purposes-first energy level holds 2 electrons; others hold 8 electrons

7 Periodic Table 92 naturally occurring elements Each row (period)-left to right-increasing # protons (increasing atomic #) Vertical columns (groups) elements w/ similar chemical properties Location on PT allows us to predict how it will react w/ other elements

8 Isotopes Identity of an atom depends only on # of protons, not on the # of neutrons Isotopes: atoms w/ same # of protons, different number of neutrons different masses Mass number: the sum of numbers of protons & neutrons

9 Practice Potassium (K) protons (how found? ) electrons (how found? ) neutrons (how found? )

10 Common Isotopes Hydrogen-3 isotopes (deuterium, tritium) Carbon (12, 14-Carbon Dating) Uranium (238, 235) Radioactive, Nuclear weapons.

11 Compounds Compound: substance that contains atoms of 2/more elements that are chemically combined Atoms tend to be more stable when their outermost (valence) energy level is full Noble Gases Atoms fill outer shell by gaining, losing or sharing electrons Forms a chemical bond

12 3 Types of Bonds Covalent, Ionic, Metallic Covalent: -share electrons (to fill valence shells for both atoms) 2/more atoms held together by covalent bonds form molecule Ex. water, CO₂ Atoms of same element also form covalent bonds w/ each other to form molecules Ex. N₂ ; O₂

13 Ionic Bonds Compounds held together by force of electrical attraction b/w atoms that have lost or gained electrons (ions) If atom gains 1/more e-becomes charged If atom loses 1/more e-becomes + charged Charged atom = ion Opposite charged attract each other; ions bond to form compounds Force of attraction holds atoms together Ex. NaCl(Na +; Cl -)

14 NaCl(drawn out)

15 Metals & Nonmetals Metal-an element that loses e-easily to form + ions = cations Ionic compounds do not form between metals Nonmetal-gains e-easily to form a ion = anion Ionic Compounds form b/w a metal + nonmetal

16 Metallic Bonds Bonds formed b/w metals In pure metallic minerals such as Iron exist as + ions Rather than moving distinctly around nucleus, outer e-move freely around all positive ions aka sea of electrons Free movement of e-around metal ions accounts for some typical properties of pure metals, such as high conductivity

17 Mixtures & Compounds Mixture: individual elements or compounds keep their own properties + can be present in any proportion. Can be separated by physical means Ex salt water Can be separated by evaporating H₂O Elements in compound separated by chemical means Ex. H₂O Separated by breaking chemical bonds w/ strong electric current