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Electron Shells
Those crazy electrons, they’re always moving! They spin very quickly around the nucleus. As the electrons
spin, they can move in any direction, as long as they stay in their _____________. Any direction you can imagine
- upwards, downwards, or sideways - electrons can do it. The atomic shell, also called an _________________, is
the distance from the nucleus that the electron spins. If you
are an electron in the first shell, you are always closer to the
nucleus than the electrons in the second shell. Electrons can
spin around the nucleus of an atom in any direction.
There are a couple of ways that atomic orbitals are named. One method is
called the SPDF system. Another method uses specific letters (k, l, m, n,
o, p, and q) for each shell. For now, we’ll just worry about the first 3
shells & will call them the ________ shell, ________ shell, & ________ shell.
Each shell can only hold a certain number of electrons. The first shell can only
hold ____, the second can only hold ____, and the third can hold up to ______.
Shell
Number
1
2
3
Possible # of
Electrons
The outermost shell in an atom is called the valence shell. The outermost
electrons are called ______________ electrons. They’re super important, because
they are the only electrons that are allowed to _____________ with other atoms.
If I ask you how many valence electrons are in an atom, you’ll tell me how many electrons are found in the
outermost of all the shells.
Possible Test Question: How many valence electrons are in Lithium atom? Well, one way to solve this question
is by drawing what a Lithium atom looks like. We call these types of pictures Bohr Diagrams. Let’s practice.
Steps to Drawing an Atom
1. Find the element on the periodic table.
2. Determine how many protons, neutrons, and electrons it has
3. Draw a nucleus with protons & neutrons
4. Draw the electrons in their correct shells
•
•
Remember, only 2 electrons can go in the 1st shell, 8 in the 2nd , and 18 in the 3rd
Also, try to pair electrons & place them at the very top, bottom, left, or right (like a compass)
Example #1: _________________
Example #2: _________________
p+ = ___
p+ = ___
no = ___
no = ___
e- = ___
e- = ___
Draw the Bohr Diagrams for the following atoms:
Hydrogen
Boron
+
+
p = ___
o
n = ___
no = ___
e- = ___
e- = ___
p = ___
Nitrogen
Oxygen
p+ = ___
p+ = ___
no = ___
no = ___
e- = ___
e- = ___
Neon
Sodium
Sulfur
Argon