Atomic Models Withrow High School Chemistry

3 basic sub-atomic particles

Subatomic particles include the protons which have a positive charge and neutrons which have no charge

Both of these (the proton and the neutron) are both found in the center of the atom which is called its nucleus

Protons and neutrons in the nucleus have an overall positive charge

Outer layers are filled with electrons which have a negative charge

Electrons must equal protons so the overall charge on the atom is 0

Atoms that have a different number of neutrons in the nucleus are called ISOTOPES All carbon has 6 protons and 6 electrons Carbon with 6 protons and 5 neutrons is C-11 Carbon with 6 protons and 7 neutrons is C-13 Isotope Half Life C minutes C-12Stable C-13Stable C years C seconds

2. The number of protons and neutrons in the nucleus is called the ATOMIC MASS. This number is an average of all of the isotopes of that element and therefore contains a decimal. Isotope Half Life Be days Be-9Stable Be years Atomic Mass: amu

3. The atomic number refers to the number of protons in the nucleus which must also always be equal to the number of electrons.

4. The identity of the element and its physical properties is determined by the number of protons Symbol: Fe Atomic Number: 26

5. The chemical properties of an element are determined by the number and layers of the electrons. This is called the electron configuration of the element.

6. The energy levels of an atom’s electrons are determined by the row of periodic table

7. Only the OUTER electrons are ever involved in a chemical reaction. Third Energy Level: 3

8. The first energy level has one (1) sublevel called S. It can hold a maximum of 2 electrons.

9. The second energy level has 2 sublevels called s (which can hold 2 electrons) and the p which can hold 6 electrons. Between them they can hold a maximum of 8 electrons.

10. The third energy level has 3 sublevels called the s with 2 electrons, the p with 6 and the d with 10 for a total of 18 electrons.

11. The fourth energy level has 4 sublevels called the s with 2 electrons, the p with 6, the d with 10 and f with 14 for a total 32 electrons.

12. S sublevels are spherical shaped and have 1 orbital which can hold 2 electrons spinning in opposite directions. The s sublevel must fill before the p can have any electrons.

13. P sublevels are dumb-bell shaped and have 3 orbitals which can hold 2 electrons spinning in opposite directions. Each orbital must have one electron in it before any of them can have 2 electrons. Usually the p sublevel must be full before the d gets any electrons.

14. D sublevels are p + doughnut shaped and have 5 orbitals which can each hold 2 electrons spinning in opposite directions. Each orbital must have one electron in it before any of them can have 2 electrons.

ATOMIC ORGANIZATION ElementSymbolAtomic Mass with decimal Atomic Mass rounded Atomic Number neutrons = mass- number hydrogen Helium Lithium Beryllium Boron carbon