Protons are postively charged and are inside the nucleus. (the # of protons = the atomic number)
Neutrons are neutral and are also in the nucleus.
The # of protons + # of neutrons = Mass Number (the number below the atomic symbol)
Electons have a negative charge and are found outside the nucleus!
  • Over 100 elements, 92 are naturally occuring.
  • Each element has a unique name and symbol.

  • The periodic table of elements
  • horizontal rows are called periods.
  • vertical columns are called groups.

  • isotopes are when you have an unexpected number of neutrons
  • atoms have the same element that have the same number of protons and electrons but have a diffrent number of neutrons.
  • carbon 14 is used for carbon dating.

  • when a nuclues breaks apart, it gives off radiation that can be detected and used for many applications.
  • RADIOACTIVE ISOTOPES ^^^

USES IN BIOLOGY :
  • determine the age of rocks and fossils
  • irradiation of food to kill bacteria
  • radiation treatment for cancer
  • tracers and labels to detect disorders


COMPOUNDS:
  • when two or more elements are combined
  • from a specific combination of elements in a fixed ratio
  • cannot be broken down into simpler compounds or elements by physical means.
EX. carbohydrates C1;H2;O1
(gluclose is C6;H12;O6)


CHEMICAL BONDS;
  • covalent bonds are chemical bonds that form when electons are shared.
  • a molecule is a compound in which the atoms are held together by covalent bonds.

IONIC BONDS:
  • electrical attraction between two atoms or groups of atoms.
  • water has two polar covalent bonds. So water is called a "polar" molecule.
  • when slightly positive and negative regions pull on the molecules and hold them together.
  • depends on the size of the molecule, its shape, and its ability to attract electrons.
(van der waals forces)
  • diffrent atoms do not have the same ability to attreact electrons.
  • some atoms have a stronger attraction for electrons than others.
  • therefore, the sharing of electrons between two atoms in a covalent bond is not always equal (like Tommy's X-box isn't shared equally with his little brother)