Question

An element A atomic number 7 mass number 14

B electronic configuration 2, 8, 8

C electrons 13, neutrons 14

D Protons 18 neutrons 22

E electronic configuration 2, 8, 8, 1

State (i) valency of each element (ii) which one is a metal (iii) which is a non-metal (iv) which is an inert gas.

Answer 1

• Element A
  Atomic number = 7 = Number of electrons = 2, 5
  Valency of A =- 3 (Nonmetal)
• 
  Element B
  Electronic configuration 2, 8, 8
  Valency of B = Zero (Inert gas)
• 
  Element C has 13 electrons
  Electronic configuration = 2, 8, 3
  Valency of C = +3 (metal)
• 
  Element D
  Protons = 18 = Electrons = 2, 8, 8
  Valency of D = Zero (inert gas)
• 
  Element E
  Electronic configuration = 2, 8, 8, 1
  Valency of E = +1 (Metal)
• C and E are metals.
• A is a non-metal.
• B and D are inert gases