Question

inner transition elements in the first period​

Answer 1

Answer:

• The first of the inner transition series includes the elements from cerium (symbol Ce, atomic number 58) to lutetium (symbol Lu, atomic number 71).
• These elements are called the lanthanoids (or lanthanides) because the chemistry of each closely resembles that of lanthanum.

Answer 2

Answer:

Explanation:

(i) Elements placed in two separate rows at the

bottom of the periodic table are called inner

transition elements.

(ii) They include two series of elements: Lanthanide

series and Actinide series. They belong to f-block

elements of Modern Periodic table.

(iii) 14 elements with atomic number 58 to 71

(Cerium to Lutetium) are called lanthanides.

These elements are placed along with lanthanum

(La = 57) in group 3 and period 6 because of very

close resemblance in properties between them.

(iv) 14 elements with atomic number 90 to 103

(Thorium to Lawrencium) are called actinides.

These elements are placed along with actinium

(Ac = 89) in group 3 and period 7 because of very

close resemblance in their properties.

(v) They have last three shells incompletely filled.