SK015 | MeKa | Chapter 2.0 | Atomic Structure

CHEMISTRY SK015
2021/2022

SUGGESTED ANSWER TOPIC 2: ATOMIC STRUCTURE

MEKA
2.1: Bohr’s Atomic Model
1.

• When energy is absorbed, the electron at the ground state will absorb the energy and
excited to higher energy level.

• This excited electron is unstable. So it will fall back to lower energy level (n=1) and emit
certain amount of energy with certain wavelength and frequency.

2. (a) n=5 to n=1

(b) Ultraviolet region

(c) ni= 4, nf = 1

∆ = ( 1 2 − 1 )
2

= 2.18 × 10−18 (412 − 1 )
12

= -2.04 x 10-18 J

(d) ∆E = hc

λ

2.04 x 10-18 J = (6.63 x 10-34 Js-1)(3.00 x 108 ms-1)
λ

λ = 9.73 x 10-8 m
∆E = hѵ

2.04 x 10-18 J = (6.63 x 10-34 Js-1) ѵ
ѵ = 3.08 x 1015 s-1

3. ni = 6, nf = 2

1 = ( 1 12 − 1 ) , 1 < 2
22

= 1.097 × 107 −1 (212 − 612)

λ = 4.102 x 10-7 m

CHEMISTRY SK015
2021/2022

SUGGESTED ANSWER TOPIC 2: ATOMIC STRUCTURE

2.2: Quantum Mechanical Model & 2.3: Electronic Configuration

1 (a) n=3, l=0, m=0, s=+1/2 n=3, l=0, m=0, s=-1/2

n=3, l=1, m=0, s=+1/2 n=3, l=1, m=-1, s=+1/2

(b) 1s22s22p63s23p2

(c)

zz z

x yx yx y
3s
3px 3py
2. (a) V2+:

1s 2s 2p 3s 3p 3d
V3+:

1s 2s 2p 3s 3p 3d

(b) n=3, l=2, m=-2, s=+1/2 or n=3, l=2, m=-2, s=-1/2 or

n=3, l=2, m=-1, s=+1/2 or n=3, l=2, m=-1, s=-1/2 or

n=3, l=2, m=0, s=+1/2 or n=3, l=2, m=0, s=-1/2 or

n=3, l=2, m=+1, s=+1/2 or n=3, l=2, m=+1, s=-1/2 or

n=3, l=2, m=+2, s=+1/2 or n=3, l=2, m=+2, s=-1/2

choose 1 only.

3. (a) Chromium
Expected: 1s22s22p63s23p64s23d4
Actual: 1s22s22p63s23p64s13d5

Copper
Expected: 1s22s22p63s23p64s23d9
Actual: 1s22s22p63s23p64s13d10

CHEMISTRY SK015
2021/2022

SUGGESTED ANSWER TOPIC 2: ATOMIC STRUCTURE

(b) Chromium: half-filled 3d orbital is more stable than partially-filled 3d orbital.
Copper: completely-filled 3d orbital is more stable than partially-filled 3d orbital.