What to know
-Columns, groups or families:
how many valance electrons (electrons in last energy level) present
-Rows or periods: how many energy levels there are
e.g-If you are in gr.3 you will have: 3 valence electrons
e.g-If you are in per. 4 you will have: 4 energy levels
are limits to the amount of electrons that an energy level can hold these are them:
EL #1(floor) = 2e-
EL #2 (floor) = 8e-
EL #3 (floor) = 18e-
EL #4 (floor) = 32e-
Number (#): number of Protons (p+) and Electrons (e-)
Mass(Mass number):Atomic Mass Atomic Number = number of neutrons
How to do
a Bohr Model:
-Pick an element, in
this case Magnesium (Mg)
-Then draw a nucleus:
-Round off your atomic mass to the nearest whole number and write it down next to the atomic
-Then write down which group and period it is in using your Periodic Table of the Elements:
-Knowing the Period you are in, in this case Per. 3, draw the necessary number of energy levels.
Using the group number it is in write down how many valence electrons you will have.
-Using the Atomic number, 12 for Mg, write
down inside the nucleus how many p+s you will have. Then fill in your first two energy levels with the remaining e-s, but
respect their maximum amount. Remember that Atomic number tells you how many protons AND electrons you have.
-Finally, subtract you Atomic number, 12 in this case, from your Atomic mass, 24, to tell you how
many neutrons you will have in your nucleus. Then write it in your nucleus.
24-12 = 12 (neutrons)