Question

2. The atomic numbers of three elements A, B and C are 12, 18 and 20 respectively. State, giving
reason, which two elements will show similar properties

Answer 1

The elements are,
A-(Atomic number 12) = Magnesium
B-(Atomic number 18) = Argon
C-(Atomic number 20) = Calcium

Element Calcium and magnesium will show similar properties as they belong to the same group (Group II) of the periodic table. They have the same number of valence electrons and they both are metals. While argon is a noble gas.

Answer 2

first do electronic configuration
A-2,8,2
B-2,8,8
C-2,8,8,2
so A and C have equal valency lies in similar group so they how similar properties