5. The atomic number and mass number of atoms of five elements are given below:
Element
Atomic Number
Mass Number
A
3
7
7
14
C C
8
18
IT o
D
9
19
17
37
(a) What is the valency of each of these five atoms?
(b) Which of these contains the greatest number of neutrons?
(c) Which of these contains the least number of electrons?
(d) Which of these contains equal number of electrons and neutrons?
Answers
Answer:
1.The sulphur atom has 6 electrons in the outermost shell, and its valency could be 6. But it is easier for sulphur to gain two electrons instead of losing six electrons. Hence, its valency is determined by subtracting six electrons from the octet and this gives a valency of two for sulphur.
2.The atom with the largest number of neutrons is a tie between livermorium and tennessine. Each of these atoms contain 177 neutrons
3.The number of neutrons is the difference between the mass number and atomic number.
92
235
U contains the least number of neutrons
The number of neutrons in
92
235
U =235−92=143
The number of neutrons in
92
238
U =238−92=146
The number of neutrons in
93
239
Np =239−93=146
The number of neutrons in
93
240
Np =240−93=147
Answer:
a) Valency of A: 1
Valency of B:- 3
Valency of C: 2
Valency of D: 1
Valency of E: 1