## Chem – Quantum Numbers (Part 5)

What sections should I know before attempting to learn this section?

How do we use the 4 different types of quantum numbers together in one answer?

Now that we know what each quantum number means we also want to be able to put all the different quantum numbers together to answer one question.  You may have noticed that I have used the exact same elements as my example problems for all the different quantum categories. That is because for most questions asked about quantum numbers they usually go one of two ways. Tests tend to ask either what are the all the quantum numbers for the last electron in a certain element? Or they tend to ask what are the possible quantum numbers given in each of the quantum categories? We will go through each type of question below.

The first question, what are all the quantum numbers for the last electron in a certain element is answered by analyzing the energy level (n), orbital type (L), specific orbital (mL), and spin of the electron (ms). This is very similar to the practice problems we have had so far it is just combining them all into one.

Remember to use the periodic table links like your regular periodic table handy.  Also if you need it have the quantum periodic table and the energy level periodic table ready.

VIDEO Quantum Number Demonstrated Example 1: What are the quantum numbers for the last electron of phosphorus? Remember to use these periodic table links if you need them.

Step 1:

What energy level is phosphorus in?

Answer: The third energy level…..so n = 3

Step 2:

What orbital type is phosphorus in?

Answer: The p orbitals…..so L = 1

Step 3:

What specific orbital is phosphorus in?

Answer: The second p orbital…..so mL = 1

Step 4:

What is the spin of the last electron in phosphorus?

Step 5:

What are the quantum numbers for the last electron of phosphorus?

COMPLETE ANSWER: n = 3, L = 1, mL = 1, ms = -1/2

VIDEO Quantum Number Demonstrated Example 2: What are the quantum numbers for the last electron of yttrium?  Remember to use these periodic table links if you need them.

Step 1:

What energy level is yttrium in?

Answer: The fourth energy level…..so n = 4

Step 2:

What orbital type is yttrium in?

Answer: The d orbitals…..so L = 2

Step 3:

What specific orbital is yttrium in?

Answer: The first d orbital…..so mL = -2

Step 4:

What is the spin of the last electron in phosphorus?

Step 5:

What are the quantum numbers for the last electron of phosphorus?

COMPLETE ANSWER: n = 4, L = 2, mL = -2, ms = -1/2

Examples: What are the quantum numbers for the last electron of each element below?  Remember to have your regular periodic table handy.  Also if you need it have the quantum periodic table and the energy level periodic table ready.

 Ca n = 4, L = 0, mL = 0, ms = +1/2 Mo n = 4, L = 2, mL = 1, ms = -1/2 In n = 5, L = 1, mL = -1, ms = -1/2

PRACTICE PROBLEMS: What are the quantum numbers for the last electron of each element below?  Remember to have your regular periodic table handy.  Also if you need it have the quantum periodic table and the energy level periodic table ready.

 Si n = 3, L = 1, mL = -1, ms = -1/2 O n = 2, L = 1, mL = 0, ms = +1/2 Mn n = 3, L = 2, mL = 2, ms = -1/2 Rb n = 5, L = 0, mL = 0, ms = -1/2 Th n = 5, L = 3, mL = -2, ms = -1/2 Kr n = 4, L = 1, mL = 1, ms=+1/2  