Question

Identify correct set of atomic numbers belongs to transition elements series
1) 9,21,25,72
2) 21,25,29,57
3) 21,25,30,57
4) 29,48,57,72​

Answer 1

Answer:

21,25,29,57

Explanation:

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Answer 2

Answer:

• The correct set is 21, 25, 29, 57

Explanation:

$\rule{300}{1.5}$

Let's write the electronic configuration of each elements given to us,

Element having Atomic number 9:

• [He] 2s² 2p⁵

Element having Atomic number 21:

• [Ar] 4s² 3d¹

Element having Atomic number 25:

• [Ar] 4s² 3d⁵

Element having Atomic number 29:

• [Ar] 4s¹ 3d¹⁰

Element having Atomic number 30:

• [Ar] 4s² 3d¹⁰

Element having Atomic number 48:

• [Kr] 5s² 4d¹⁰

Element having Atomic number 57:

• [Xe] 6s² 5d¹

Element having Atomic number 72:

• [Xe] 6s² 5d² 4f¹⁴

And, from the definition of transition elements we know that they must have incompletely d orbitals in its ground state or in the most common oxidation state.

Therefore, Elements having atomic number 21, 25, 29, 57 and 72 are Transition elements.

So, Correct set is 21, 25, 29, 57  (Option - b).

$\rule{300}{1.5}$