Chapter 3.1 Chemistry of Life….

Atom – basic unit of matter It is the simplest unit of matter with its own physical and

chemical properties

Made up of sub atomic particles Neutrons (+/-) Protons (+) Electrons (-)

The number of electrons and protons are the same giving the atom a neutral charge

Atom’s Structure

1. Nucleus Contains Protons and Neutrons

Has a positive chargeProtons and Neutrons have the same mass

2. Electron Cloud Electrons are located here They are in constant motion Very small

Electrons

Very energetic Very small Move at high speeds

around the nucleus in random directions

Different energy levels in the electron cloud

Electrons (continued)

Energy levels The levels farther from

the nucleus have more energy

To make most atoms stable their outer energy level must be filled with eight electrons

Electrons can gain/lose energy by switching levels

Elements

Composed of entirely the same type of atoms More than 100 elements

90 % of living things are composed of Oxygen, Carbon, Hydrogen, and Nitrogen

Each element has a symbol

Arranged in the periodic table

Elements continued…

The amount of protons in an atom is its atomic number

Compounds

Most elements do not naturally exist by themselves

Compounds Pure substances that are made up of atoms of

two or more elements

Chemical Equations show the ratios H2O & C2H3O2

Compounds (continued)

When elements combine their physical properties change Sodium + Chlorine

Sodium in natural form is highly volatile

Chlorine is poisonous Together they form table

salt

Compounds (continued)

Most elements combine to fill outer energy levels with eight electrons

Elements with less than eight atoms in their energy levels tend to undergo chemical reactions Form new bonds with other atoms

Covalent Bonds

Def. – a bond that forms when two atoms share one or more pairs of electrons

SHARING OF ELECTRONS Molecules

A chemical structure composed of one or more atoms

Water – it is always one 2 hydrogen atoms and 1 oxygen atoms

Ionic Bonds

An ionic bond is formed when one atom gives up an electron to another. The positive ion is then attracted to a negative ion to form the ionic bond