---

Atoms

Atom - the smallest particle of an element which can enter into a chemical combination.
Periodic Table of Elements - list of all known elements.
- NIST Periodic Table of Elements (PDF file)
Atoms can be broken down into smaller parts.
Requires nuclear reactions or electromagnetic interactions to breakdown an atom.

Atomic Structure

Three particles:
Proton - particles with a positive charge - located in nucleus.
Neutrons - particles with a neutral charge - located in nucleus.
Electrons - particles with a negative charge.
Located in a roughly spherical zone around the nucleus.

Atomic Number and Symbol

Atomic number is the number of protons in the nucleus.
All atoms of same element will have same number of protons.
Atomic symbol is the letter designation for a given element:
C - Carbon
O - Oxygen
Cl - Chlorine
Na - Sodium (natrium)
Fe - Iron (ferrum)
Au - gold (aurum)

Atomic Mass

Atomic Mass is sum of masses of all atomic particles.
proton - 1.6 x 10^-27 kg
neutron - 1.6 x 10^-27 kg
electron - 1 x 10^-30 kg
Atomic Mass Number is based on each proton and neutron having a mass of 1.
Oxygen has 8 protons and 8 neutrons - atomic mass of 16.

Isotopes

Atomic mass number for Oxygen on the Periodic Table of Elements?
Every oxygen atom must have 8 protons.
The number of neutrons in the nucleus can change.
O¹⁶ - 8 protons, 8 neutrons
O¹⁷ - 8 protons, 9 neutrons
O¹⁸ - 8 protons, 10 neutrons
O¹⁷ and O¹⁸ are isotopes of oxygen.

Chemical Bonding

Atoms are normally grouped in molecules.
Bonding of atoms occurs because of interactions between electrons of neighboring atoms.
Most free atoms have too many or too few electrons.
This results in an atom that is either negatively or positively charged - an ion.
Ionic Bonds result when one atom gives up an electron to another atom - weak bonds.
Covalent Bonds result when two atoms share an electron - very strong bonds.
Metallic Bonds result when electrons are shared by a large number of atoms - electrons are free to move.
Van der Waals Bonds develop because the zone around an atom in which the electrons are found is not spherical - electrical charges develop

Minerals

Mineral - A naturally occurring, inorganic solid with a definite chemical composition and a regular internal crystalline structure.

Naturally Occurring

Inorganic

Solid

Chemical Composition

Some minerals contain only certain elements:
Halite - NaCl
Quartz - SiO₂
Orthoclase - KAlSi₃O₈
Some minerals have a range of compositions:
Olivine - (Mg,Fe)₂SiO₄
Hornblende - (Ca,Na,K)_2-3(Mg,Fe,Al)₅(Si,Al)₈O₂₂(OH)₂

Regular Internal Crystalline Structure

Atoms and molecules are arranged in a regular, repeating pattern.
• Example 1
• Example 2
Crystal structures form because the arrangement is the most stable for those atoms or compounds.

 

---