2.2.1 - Electronic Structure

Question 1

What was an early model of the atom?

Answer 1

The Bohr model (GCSE model) with electrons in spherical orbits.

Question 2

How are electrons arranged in the Bohr model?

Answer 2

In shells: 2 in the first shell, 8 in the second, 8 in the third, 8 in the fourth

Question 3

What did early models predict about noble gas electron arrangements

Answer 3

That atoms and ions with noble gas configurations should be stable.

Question 4

What does the A-level model of the atom include?

Answer 4

Principle energy levels, sub energy levels (s, p, d, f), and orbitals

Question 5

What are principal energy levels?

Answer 5

Energy levels numbered 1, 2, 3, 4… with 1 being closest to the nucleus

Question 6

What does the principal quantum number indicate?

Answer 6

The shell occupied by the electrons

Question 7

What are sub-energy levels?

Answer 7

s, p, d, f – they are within each principal energy level.

Question 8

How many electrons can each sub-level hold?

Answer 8

s: 2 electrons
p: 6 electrons
d: 10 electrons
f: 14 electrons.

Question 9

How many orbitals can each sub-shell hold?

Answer 9

S: 1 orbital
P: 3 orbitals
D: 5 orbitals
F: 7 orbitals

Question 10

What is a shell?

Answer 10

A group of orbitals with the same principal quantum number.

Question 11

How many electrons can an orbital hold?

Answer 11

Up to 2 electrons of opposite spin.

Question 12

How many electrons can the 1st shell hold?

Answer 12

2 electrons

Question 13

How many electrons can the 2nd shell hold?

Answer 13

8 electrons

Question 14

How many electrons can the 3rd shell hold?

Answer 14

18 electrons

Question 15

How many electrons can the 4th shell hold?

Answer 15

32 electrons

Question 16

Why must electrons in the same orbital have opposite spin?

Answer 16

To obey the Pauli exclusion principle — no two electrons can have the same set of quantum numbers.

Question 17

How are orbitals visualized?

Answer 17

As three-dimensional shapes based on mathematical probability distributions.

Question 18

Can orbital shapes be drawn exactly?

Answer 18

No, they are approximations.

Question 19

What orbitals are found in each principal energy level?

Answer 19

Level 1: 1s
Level 2: 2s, 2p
Level 3: 3s, 3p, 3d
Level 4: 4s, 4p, 4d, 4f.

Question 20

What is the correct order of sub-level energy for filling orbitals?

Answer 20

1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p → 5s → 4d → 5p

Question 21

Why is 4s filled before 3d?

Answer 21

Because 4s is lower in energy than 3d.

Question 22

How is electronic structure written using numbers and letters?

Answer 22

By writing principal energy level, sub-level, and number of electrons. E.g., Oxygen: 1s² 2s² 2p⁴

Question 23

In the configuration “2p⁴”, what does each part mean?

Answer 23

2 = energy level, p = sub-level type, 4 = number of electrons in that sub-level.

Question 24

What do arrows in a spin diagram represent?

Answer 24

Electrons.

Question 25

What does opposite arrow direction in a spin diagram mean?

Answer 25

Opposite electron spins.

Question 26

What does each box in a spin diagram represent?

Answer 26

One orbital.

Question 27

What shape are s orbitals?

Answer 27

Spherical.

Question 28

What shape are p orbitals?

Answer 28

Dumbbell-shaped.

Question 29

How should electrons be filled into orbitals within the same sub-level?

Answer 29

Each orbital should be singly filled before pairing (Hund’s Rule).

Question 30

How is the periodic table divided by orbital filling? Pull up a periodic table and point it out?

Answer 30

Into blocks: s-block, p-block, d-block, and f-block.

Question 31

What defines an s-block element?

Answer 31

Its outer electron is filling an s sub-shell.

Question 32

What happens to electrons during the formation of positive ions?

Answer 32

Electrons are lost.

Question 33

What is the electronic configuration of Mg and Mg²⁺?

Answer 33

Mg: 1s² 2s² 2p⁶ 3s² Mg²⁺: 1s² 2s² 2p⁶

Question 34

What happens to electrons during the formation of negative ions?

Answer 34

Electrons are gained.

Question 35

What is the electronic configuration of O and O²⁻?

Answer 35

O: 1s² 2s² 2p⁴ O²⁻: 1s² 2s² 2p⁶

Question 36

Why do ions often form noble gas configurations?

Answer 36

Because they are more stable.

Question 37

Where do electrons go when sub-levels are being filled?

Answer 37

Into orbitals within sub-levels in order of increasing energy.

Question 38

When using ‘electrons in box’ representation, what shape is used to represent the electrons?

Answer 38

Arrows.

Question 39

What are the rules by which electrons are arranged in a shell? (5)

Answer 39

* Electrons are added one at a time. * Lowest available energy level is filled first. * Each energy level must be filled before the next one can fill. * Each orbital is filled singly before pairing. * 4s is filled before 3d.

Question 40

What is the electron configuration of krypton?

Answer 40

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6