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Physical Science Notes 416-436
Bohr Model
Tips and Tricks
Chemical and Physical Changes and properties
Periodic Table of the Elements: Properties of Elements
Atomic Theories and discoveries
Bohr Model
The Naming of Binary Compounds
Octet Rule/Elemental Happiness
Balancing Chemical Equations
pH Math
Acid Rain
Review Questions
Review tests
Testing for H2, CO2 and O2 Lab
Conductivity Lab
Colour your world Lab
pH Lab
Isn't it Ionic Lab
Titration Lab 1 and 2
How to write a lab report
Tutoring Schedule
Fun Facts
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Niels Bohr- How to draw Bohr Models


Bohr Models


What to know first:

                -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

-There 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-

-Atomic Number (#): number of Protons (p+) and Electrons (e-)

-Atomic 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 number:

            Atomic Number              Atomic Mass

                      12                               24

-Then write down which group and period it is in using your Periodic Table of the Elements:

            Gr. 2(IIA)                       Per. 3

-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)


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