Title: Lesson 4 Full Electron Configuration

Learning Objectives:

• Know how to write full electron configurations using ideas of subshells

1. 1s22s22p4 = Oxygen 2. 1s22s22s63s1 = Sodium

3. 1s22s22p63s23p64s2 = Calcium

Below are examples of how you write electron configurations in HL chemistry. Try and figure out the

method used to produce them. Use your periodic table.

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• nth energy level is divided into n sub levels

• s, p, d and f identify the different sub levels

• Each main level can hold a maximum of 2n2 electrons

Why?

Shows the existence of sub levels within an energy level. This explains the behaviour of

elements.

Draw out the sublevels in each main energy level. Starting at 1s, follow the arrows to give the order of the sublevels!

1s2

2s2

3s2

4s2

5s2

6s2

7s2

2p6

3p6

4p6

5p6

6p6

3d10

4d10

5d10

6d10

4f14

5f14

1

2

3

4

5

6

7

So, the pattern for reading the electron configurations right off the periodic table is this:

If you are wanting to write the electron configuration for any element, just follow this pattern and remember to stop at the element you’re representing.

1s2

2s2

3s2

2p6

3p5

1

2

3

4

5

6

7

For example, Cl (#17) which is right here on the table:

So the answer would be 1s2 2s2 2p6 3s2 3p5

The short cut would be: [Ne]3s2 3p5

1s2

2s2

3s2

4s2

2p6

3p6

3d8

4f14

5f14

1

2

3

4

5

6

7

Or how about Ni (#28)

1s2 2s2 2p6 3s2 3p6 4s2 3d8

Short cut: [Ar] 4s2 3d8

1s2

2s2

3s2

4s2

5s2

6s2

2p6

3p6

4p6

5p6

6p3

3d10

4d10

5d10

4f14

1

2

3

4

5

6

7

Let’s try Bi (#83)

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2

4f14 5d10 6p3 (don’t forget the 4f14!)Short cut: [Xe]6s2 4f14 5d10 6p3

Abbreviated electron Configurations

• Only outer electrons are shown• Inner electrons are represented as a noble gas

core.• After Argon (Ar), notation can be written like:

• Potassium = [Ar] 4s1

• [Ar] represents 1s22s22p63s23p6

The Uncertainty Principle• Bohr’s model assumes the electron’s trajectory can be

precisely described = Not true.

• Any attempted measure of an electron’s position will disturb the motion.

• Focusing radiation to locate an electron will give it a ‘kick’ throwing it into a random direction.

• We cannot know where an electron would be at any given time – all we can give is a probability picture of where the electron is likely to be.

By the way, the orbitals are not really little empty boxes on a line:

2p

Instead, they are specific three-dimensional shapes called probability clouds that show where you are most likely to find the electron around the nucleus.

The s sublevels are all spherical in shape:And they just get larger and larger as you move to higher levels

1s2s3s

1s atomic orbital. Density of dots gives the probability of finding the electron in this region.

Atomic Orbitals

p OrbitalThe p orbitals are a bit more complicated - they are peanut shaped!

Within the 2p sublevel, the three orbitals are oriented at right angles to each other.

They are referred to as the 2px, 2py and 2pz orbitals.

And they fit together around the nucleus like this:

P Orbitals

Complete the Test Yourself Questions

Use the ‘Sub-levels of Electrons Table’ and ‘Electron Configuration Blocks’ to help you

• Page 69• Question 11 a-e• Check your answers on page 559

1.1s22s22s63s23p64s23d10

2.1s22s22p63s23p64s23d10

3.1s22s22p63s23p64s24d10

Which electronic configuration for Zn, Zinc, is correct?

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