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 charge Protons 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 H 2 O & C 2 H 3 O 2

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