1. Atomic Model

2. Matter Anything that has mass and volume –Mass the amount of particles making up a substance –Volume is the amount of space taken up by the particles The basic unit of matter is the atom, which is made up of protons, neutrons and electrons

3. Proton Positively charged (+) Located in the nucleus Mass number of 1 Atomic Number = Number of Protons –Atomic number on the periodic table –Gives the identity of the atom

4. Neutron No charge (neutral) Located in the nucleus Mass number of 1 Mass of atom = protons + neutrons –Must have a whole number of neutrons –Average mass can be found on the periodic table Neutron number may be different to form an isotope

5. Electron Negatively charged (-) Constantly, randomly moving around the nucleus in energy levels Mass number of 0 If the atom is neutral (has a charge of zero) then: –Proton number = electron number Electron number may change to form an ion –An atom with a + or - charge

6. Determining amount: How many protons, neutron and electrons are in an atom of Lead: 82 Pb Lead 207.2 Atomic Number Element Symbol Element Name Atomic Mass

7. Determining amount How many protons, neutron and electrons are in an atom of Lead: Number of protons = atomic number –Atomic number = 82 = # of protons Number of electrons = number of protons –82 = # of electrons Atomic mass = protons + neutrons 207.2 = 82 + x x = 125.2 must be a whole number 125 = number of neutrons

8. Try one on your own How many protons, neutrons and electrons are in an atom of silver: 47 Ag Silver 107.9 Atomic Number Element Symbol Element Name Atomic Mass

9. Model of atom Nucleus 2nd energy level _____ (can hold 8 electrons) 4th energy level _____ (can hold 8 electrons) 3rd energy level _____ (can hold 8 electrons) 1st energy level _____ (can hold only 2 electrons) An atom can only be represented by a model since the electrons are in constant random motion.

10. Model: Atom of Sulfur (S) Nucleus 2nd 8e - 4th ____ 3rd 6e - 1st 2e - Atomic number = 16 Determine total number of electrons

11. Electrons The number of electrons in the highest energy level determines the behavior and characteristics of the element Electrons in the highest energy level are valence electrons