Introduction to minerals

-Orbiting electrons: High-speed nearly “massless” particles of negative charge which orbit the nucleus.. electrons Orbiting the nucleus are electrons having essentially no mass ands a

Earth Materials: Minerals

Chapter 5 Patterns in Nature: Minerals

 1 Minerals: Why care?

 2 Atoms, ions &

isotopes of the elements

 3 Atomic bonding and the formation of

chemical compounds

 4 Minerals: the building blocks of rocks

 Internal structure in relationship to physical properties

 5 Introduction to rocks.

Today’s Lecture:

Minerals: Why care?

Examples:

➨ Aluminum: Soft drink cans

➨ Graphite (Carbon): Pencil lead and lubricant

➨ Copper: Electrical components and wire

➨ Talc: Baby powder

➨ Silver, gold, gemstones: Jewelry

➨ Silicon: Computer chips

Raw materials for nearly all of the

manufactured products we use are obtained

from minerals.

Malachite: Ore of copper and a gemstone.

Quartz: Source of silicon used

in making computer chips

Galena: Ore of lead

Gemstones!

Other reasons:

Minerals: Why Care?

➨ Rocks inform us about geologic hazards, such

as volcanic eruptions, earthquakes etc.,

enabling us to make better decisions about how

we interact with the Earth and use its resources (e.g siting and designing buildings).

➨ Rocks hold important clues for understanding

processes of weathering and erosion This

information can help us use the Earth’s

resources more effectively (e.g extraction of

mineral and petroleum resources, soil

conservation, degradation of concrete

structures, etc.)

➨ Rocks enable us to understand our past &

place our lives in proper evolutionary context

To understand minerals we need to understand matter and how it is

Solids-Atoms and molecules organized into fixed

structures with a defined shape (crystals, glass,

plastics) Atoms move (vibrate) even in a solid! Just limited in a solid

Liquids-Fluid mixtures of atoms and molecules

existing as charged atoms or molecules (e.g “ions”) Atoms in solutions can form loose associations with each through transient electronic “bonds” However, the liquid lacks a fixed structure, like that seen in

•Elements: Different types of atoms that, in their pure form, cannot be divided into other smaller

units without changing their properties

•Atom: Smallest division of an element, that still possesses the chemical properties unique

to the element

•Compounds: Two or more atoms bonded

together May be composed of atoms of the same element, or combinations of several different

elements

Bulding blocks of minerals

Atoms, elements and compounds:

Building blocks of minerals

(See Science Toolbox 5.1, page 112 of text)

What is an atom?

An atom is made up of:

-A nucleus: Central region of atom where most of

the mass resides Comprised of protons and neutrons

-Orbiting electrons: High-speed nearly “massless”

particles of negative charge which orbit the nucleus

electrons nucleus

Understanding Matter…

Nucleus contains:

Protons = Particles with a mass of 1.0 and a

positive electrical charge

Neutrons = “ “ a mass of 1.0 and a

neutral electrical charge Neutrons may

be thought of as a proton bound to an electron

electrons Orbiting the

nucleus are electrons having essentially no

mass ands a negative charge.

A simple “ Bohr” model for a single atom:

T&L: Figure 2.4 A

Understanding Matter…

Number of protons in the nucleus of an element is called Its atomic number.

Elements are distinguished from each other by their atomic

Types of Atoms and Elements

Mass Variations in Elements:

● The number of protons plus the number of neutrons

in the nucleus defines the atomic mass of the element.

● However, most elements come in different “species”- versions that differ slightly in mass because of having different numbers of neutrons in the nucleus

● These “species”of elements are called isotopes

Isotopes: Same element, different mass

Example: Carbon-14

Again… mass variations of the same element are

called “isotopes”.

Many isotopes are unstable, and disintegrate

through a process called radioactive decay

where particles and/or energy are emitted

from the nucleus

C

14

is unstable

The rate of radioactive disintegration is constant, so

they can be used as a kind of clock for dating rocks!

Isotopes: Atoms that vary in the number of neutrons in the nucleus

●Number of protons determines the type of atom

6 protons = carbon

● Number of neutrons in an atom can vary.

● Number of neutrons plus the number of protons equals the

atomic “mass”

●Here are the three isotopes of Carbon:

6 protons & 6 neutrons: mass number = 12

6 protons & 7 neutrons: mass number = 13

6 protons & 8 neutrons: mass number = 14

13C

12C

14C

How we write it

Let’s review using Carbon as an example:

Classifying the Elements

equals # of protons

6 => 6 protons

Periodic table of the elements

Elements are classified by the number of protons

in the nucleus (I.e., their atomic number)

Calcium

Oxygen Aluminum

Gold

Helium

Iron Titanium

You’ve heard of many of these elements, for example:

Classifying the Elements

When atoms give away or gain electrons, they

are no longer electrically neutral In other words, They take on an electrical charge.

Any atom possessing a charge is called an “ion”.

Atoms with a positive charge are called “cations”.

Those with a negative charge are called “anions”.

Ions: Charged Atoms

Atoms that lose or gain electrons develop a charge.

● Different elements combine to make chemical

compounds…

Example 1: water (2 hydrogen atoms + 1 oxygen atom = H2O)

Example 2: salt (1 sodium atom + 1 chlorine atom = NaCl)

~ 4000 minerals on Earth!

Making Minerals

Minerals are naturally-occurring

compounds that are classified by their:

◆ Chemical composition

◆ Internal (“atomic”) structure

-> To be considered a mineral, it must:

1 Occur naturally

What are minerals?

2 Be inorganic

3 Be a solid

5 Have a defined chemical composition

4 Possess an orderly internal structure

Definition of a mineral:

✦ Atomic Bonding

How do different elements combine to form compounds?

=> By bonding between atoms!

3 main ways:

“Ionic bonding” - loaning electrons

“Covalent bonding” - sharing electrons

“Metallic bonding” - electrons are free to move about from atom to atom

Making Compounds

Example: Sodium (Na) and Chlorine (Cl)

Atoms arrange in orderly fashion: w/ alternating sodium and chlorine

atoms, so each negative ion is surrounded by positive ions, and visa versa.

Ionic Bonding

Example: Sodium (Na) and Chlorine (Cl)

Such orderly arrangement at the atomic level produces specific shapes

in crystals at the macroscopic level that reflect the atomic structure

Crystal Form Reflects Internal Structure

The structure of minerals depends on:

◆ Size of the ions involved

◆ Electrical charge of the ions involved

Crystal Form Reflects the Internal Arrangement of Atoms