5.1 Electron Structure

Question 1

What is an electron shell?

Answer 1

• A group of atomic orbitals with the same principal quantum number (n)
• It is also called an energy level

Question 2

What is an orbital?

Answer 2

• A region around the nucleus that can hold up to 2 electrons with opposite spins

Question 3

List 4 types of orbitals.

Answer 3

• s
• p
• d
• f

Question 4

Describe s-orbitals.

Answer 4

• They are the shape of a sphere
• Every shell has 1 s-orbital

Question 5

Describe p-orbitals.

Answer 5

• They are the shape of a dumb-bell
• Each shell from n=2 and onwards contains 3 p-orbitals

Question 6

How many d-orbitals are there in each shell?

Answer 6

• From n=3 and onwards, there are 5 d-orbitals in each shell

Question 7

How many f-orbitals are in each shell?

Answer 7

• Each shell from n=4 and onwards contains 7 f-orbitals

Question 8

What is a sub-shell?

Answer 8

• A group of orbitals of the same type within a shell

Question 9

How do sub-shells compare in terms of energy?

Answer 9

• Each new sub-shell added has more energy than the previous one

Question 10

How do the relative energy levels of the sub-shells of different shells compare?

Answer 10

• The sub-shells making up the first 4 shells generally stay in order from the s-orbital in n=1 having the least energy, and so on
• However, the 3d sub-shell is at a higher energy level than the 4s sub-shell

Question 11

How does the amount of energy each sub-shell has affect the order sub-shells are filled in?

Answer 11

• Sub-shells are filled in in order of ascending energy (so 1s first, and so on)
• 4s is at a lower energy level than 3d, so it it is filled first

Question 12

What do electrons-in-box models show?

Answer 12

• Electrons are represented by arrows that the either face up or down, which indicate its spin
• The 2 electrons in the same box must have opposite spins

Question 13

Why do 2 electrons in the same orbital have opposite spins?

Answer 13

• This helps to counteract their repulsion

Question 14

How do orbitals fill, and why?

Answer 14

• All orbitals within a sub-shell have the same energy
• 1 electron therefore occupies each orbital before they start to pair up (also prevents repulsion between paired electrons)

Question 15

What order are sub-shells written in for electronic configuration?

Answer 15

• In order of shell order rather than filling order (so 3d is written before 4s)

Question 16

How does the shorthand notation for electronic figurations work?

Answer 16

• You put the name of the previous noble gas in square brackets
• You then write the rest of the electronic configuration (if it has the same configuration as a noble gas, use the noble gas before this)

Question 17

Which sub-shells are affected when atoms lose or gain electrons?

Answer 17

• The one with the most energy
• The 3d energy level falls below the 4s energy level when it is (even partially) filled
• The 4s energy level therefore loses electrons (as well as filling) before the 3d energy level

Question 18

How is the periodic table divided into blocks?

Answer 18

• The blocks correspond to the elements’ highest energy sub-shell

Question 19

What are the different blocks in the periodic table?

Answer 19

• s-block is groups 1 and 2
• p-block is groups 3 to 0
• d-block is the centre block of 10 groups