Question

Identify the symbol for the missing element in each period.

Ba

La

Hf

Answer 1

• The atomic number of Barium is 56.
• Electrons per shell are 2, 8, 8, 18, 18, 2
• Number of shells = Period number.
• Number of shells = 6.
• So, the elements belong to period 6.
• The elements belonging to period 6 are Caesium, barium, lanthanum, hafnium, etc.
• Hence, the missing element is Caesium.