Don t Panic Only 20 of the Earth s 92 naturally occuring

1
Chapter 2 Some Basic Chemistry

• Dont Panic

2
Elements of the Human Body

• Only 20 of the Earths 92 naturally occuring
  elements are found in the body.
• Each element is unique size and composition.
• Each element is represented by a symbol, H is
  for hydrogen, O is for oxygen, and Na is for
  sodium????

3
The elements

• Know the names and chemical symbols for the 18
  elements in Table 2-1, page 24.
• Note the symbol may be
• 1 letter, capitalized or
• 2 letters, the first capitalized and the second
  always lower case.

4
Atoms

• An element is made up of only one type of atom,
  i.e. each atom is unique.
• Parts of an atom, fig 2-1
• Nucleus protons () and neutrons (no charge)
• Electron cloud electrons (-) spinning in shells
  or orbits around the nucleus.

5
Atoms

• If an atom is stable the protons () the
  electrons (-) and the overall charge is 0.
• Most atoms are not stable and tend to lose, gain
  or share one or more electrons.
• Atoms that lose one or more electrons become
  positive ions, example Na .
• Atoms that gain one or more electrons become
  negative ions, example Cl- .