Topic-2 (Atomic structure, Periodic table trends, mass spectrometry) IAL Chemistry

describe the shapes of s and p orbitals

- s orbitals are spherical shaped

- p orbitals are dumbbell shaped.

B, because

Give the energy level of orbitals (the pyramid) until

5th quantum shell/ principle level .

1s

2s, 2p

3s, 3p, 3d

4s, 4p, 4d, 4f

5s, 5p, 5d

State how many orbitals and electrons are there in s,p,d,f subshell

s = 1 orbital (2 electrons)

p = 3 orbitals (3x2 = 6 electrons)

[px, py, pz]

d = 5 orbitals (5x2 = 10 electrons)

f = 7 orbitals (7x2 = 14 electrons)

Give the order of subshells in increasing energy

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

(note that 4s comes before 3d because it has lower energy. so its like 4s and 4p in between 3d.)

- Use the pyramid type diagram with arrows to help figure out energy levels

Give the electronic configuration of Ca atom (atomic no = 20)

1s2, 2s2, 2p6, 3s2, 3p6, 4s2

Give the electronic configuration of Fe 2+ ion (atomic no = 24)

step 1→ write Fe atom(26) configuration:

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d6

step 2 → Fe 2+ ion config:

remove the 2 electrons in 4s orbital to give final answer:

1s2, 2s2, 2p6, 3s2, 3p6, 3d6

(Because 4s orbital electrons are in the outermost shell & so they are removed first when forming +ve ions)

give configuration for cl- ion (18)

cl atom (17)

1s2, 2s2, 2p6, 3s2, 3p5

so cl- ion: 1s2, 2s2, 2p6, 3s2, 3p6 (1 more electron added)

Give electronic configuration for the 2 atoms that are exceptions:

1. Cr (24)

2. Cu (29)

box notation electronic configuration for copper

An OH- ion has 9 protons. State how many neutrons and electrons it has.

neutron number = 8

( oxygen has 8 neutrons & hydrogen has 0 neutrons)

electron number = 10

(9 protons = 9 electrons initially and then add 1 as its negatively charged, so 9+1 = 10)

Explain why first Ionization energy of oxygen is less than nitrogen (3marks)

- the electron being removed in oxygen is paired in the 2p orbital

(while the electron being removed in nitrogen is unpaired electron)

- less energy is needed to remove a paired electron compared to an unpaired electron

- because paired electrons repel each other

Nitrogen (7) --> 1s2, 2s2, 2p3

(p orbital has 1 pair of e- and 1 unpaired electron)

Oxygen (8) --> 1s2, 2s2, 2p4

(p orbital has 2 pairs of electron)

state the variation/trend in ionic radius down the group for the 7 groups:

groups 1 to 6, ionic radius increases down the group

[NOTE --> Down any group where ions are formed, ionic radius increases because:

more electron shells added

more shielding

outer electrons further from nucleus

(for group 7/0, since they are noble gases they dont form ions)

B

( biggest peak is at 28 but answer can't be 28.0 exactly, must be slightly higher as there are peaks at 29 and 30 also)

state the trend with IE and atomic radius across period 2 and 3

- IE increases across period 2 and 3

(so m.p also increases until Carbon for period 2 and Al for period 3, cuz after its gases and they have lower M.P)

- atomic radius decreases

( because across a period the nuclear charge increases, so the outer shell is pulled closerto the

nucleus)

state the trend for ionic radius of metal ions across Period 2 and 3

Metal ion radius decreases across the period (for period 2 and 3)

• Na⁺ is largest

• Mg²⁺ is smaller

• Al³⁺ is smallest

(Number of protons increases across the period → stronger nuclear attraction

• The ions have the same number of electron shells (isoelectronic)

• More protons pull the electrons closer to the nucleus)

state the trend for ionic radius gaseous ions across a period (like Period 2 and 3)

Ionic radius of gaseous ions decreases across the period

In mass spectrometry, the ion with the greatest deflection is the one with the smallest m/z ratio

m/z= mass of ion/ charge of ion​

out of F-, Na+, Mg2+ and O2-, which has smallest ionic radius?

notice they all have 10 electrons

For isoelectronic ions:
more positive charge → smaller radius

ans: Mg2+

State what is meant by the term orbital (2marks)

- a region within an atom

- where the probability of finding an electron is highest

Describe what can be deduced about the electronic structure of sodium from its successive ionisation energies.
[3 marks]