The electronic configuration of Gadolinium (Z=64) is?

1. The electronic configuration of Gadolinium (Z = 64) is? +

Answer

[Xe] 4f⁷ 5d¹ 6s²

Detailed Explanation

Gadolinium (Gd) has atomic number Z = 64, so a neutral Gd atom contains 64 electrons.

Gd: [Xe] 4f⁷ 5d¹ 6s²

The xenon core accounts for 54 electrons:

[Xe] = 54 electrons

Remaining electrons:

64 − 54 = 10 electrons

These are arranged as:

4f⁷ + 5d¹ + 6s² = 7 + 1 + 2 = 10

Therefore: [Xe] 4f⁷ 5d¹ 6s²

Important: Gadolinium is an important exception in the lanthanoid series. The half-filled 4f⁷ subshell is particularly stable, so one electron occupies the 5d orbital rather than giving the commonly expected 4f⁸ arrangement.

Electron Distribution

4f⁷ Half-filled
7 electrons

5d¹ One electron
in d-orbital

6s² Two electrons
in s-orbital

Z = 64 Total
64 electrons

Quick Exam Trick

For Gd:

Z = 64 = 54 + 10

Remember the special stable arrangement:

Gd → [Xe] 4f⁷ 5d¹ 6s²

The key point is the half-filled 4f⁷ subshell.

30 Related MCQs with Solutions

1. The electronic configuration of Gadolinium (Z = 64) is:

A. [Xe] 4f⁸ 6s²

B. [Xe] 4f⁷ 5d¹ 6s²

C. [Xe] 4f⁶ 5d² 6s²

D. [Xe] 4f⁷ 6s³

Answer: B
Gd has the stable configuration [Xe] 4f⁷ 5d¹ 6s².

2. The atomic number of Gadolinium is:

A. 62

B. 63

C. 64

D. 65

Answer: C. 64

3. Gadolinium belongs to which series?

A. Actinoids

B. Lanthanoids

C. Transition metals only

D. Noble gases

Answer: B. Lanthanoids

4. How many electrons are present in the [Xe] core?

A. 36

B. 46

C. 54

D. 64

Answer: C. 54

5. How many electrons remain outside the xenon core in Gd?

A. 8

B. 9

C. 10

D. 11

Answer: C. 10
64 − 54 = 10.

6. Which subshell is half-filled in Gadolinium?

A. 5d

B. 4f

C. 6s

D. 5p

Answer: B. 4f⁷

7. The maximum number of electrons in an f-subshell is:

A. 6

B. 10

C. 14

D. 18

Answer: C. 14

8. The half-filled f-subshell contains:

A. 5 electrons

B. 6 electrons

C. 7 electrons

D. 8 electrons

Answer: C. 7 electrons

9. Which configuration represents the stable ground state of Gd?

A. [Xe] 4f⁸ 6s²

B. [Xe] 4f⁷ 5d¹ 6s²

C. [Xe] 4f⁶ 5d² 6s²

D. [Xe] 4f⁷ 5d² 6s

Answer: B

10. The exceptional configuration of Gd is mainly associated with:

A. Completely filled p-subshell

B. Half-filled 4f subshell

C. Empty 6s subshell

D. Filled 5d subshell

Answer: B

11. Gadolinium is placed in the:

A. s-block

B. p-block

C. d-block

D. f-block

Answer: D. f-block

12. Gadolinium is a member of the:

A. 3d series

B. 4d series

C. lanthanoid series

D. actinoid series

Answer: C

13. Which orbital receives the exceptional electron in Gd?

A. 4f

B. 5d

C. 6p

D. 5p

Answer: B. 5d

14. How many electrons occupy the 4f subshell of Gd?

A. 6

B. 7

C. 8

D. 14

Answer: B. 7

15. How many unpaired electrons are present in the 4f⁷ subshell of Gd?

A. 0

B. 1

C. 5

D. 7

Answer: D. 7
According to Hund's rule, the seven f orbitals each contain one electron.

16. Which principle explains the maximum stability of half-filled subshells?

A. Aufbau principle

B. Hund's rule

C. Heisenberg principle

D. Pauli principle only

Answer: B. Hund's rule
Hund's rule helps explain the stability associated with maximum unpaired-electron arrangement, although exchange energy is the deeper energetic explanation.

17. Which noble gas core is used for Gadolinium?

A. Kr

B. Xe

C. Rn

D. Ar

Answer: B. Xe

18. The atomic number of Xenon is:

A. 36

B. 48

C. 54

D. 56

Answer: C. 54

19. Which pair has exceptional electronic configurations?

A. Gd and Lu

B. Na and Mg

C. Ne and Ar

D. Cl and Br

Answer: A
Gd and Lu are notable lanthanoid configuration exceptions.

20. Gd has how many electrons in its 6s orbital?

A. 0

B. 1

C. 2

D. 3

Answer: C. 2

21. Which is the correct electron count for [Xe] 4f⁷ 5d¹ 6s²?

A. 62

B. 63

C. 64

D. 65

Answer: C. 64

22. Gadolinium belongs to which period?

A. 4

B. 5

C. 6

D. 7

Answer: C. Period 6

23. Which subshell has seven orbitals?

A. s

B. p

C. d

D. f

Answer: D. f

24. The value of l for an f-subshell is:

A. 0

B. 1

C. 2

D. 3

Answer: D. 3

25. How many orbitals are present in a 4f subshell?

A. 3

B. 5

C. 7

D. 9

Answer: C. 7

26. The maximum number of electrons in each orbital is:

A. 1

B. 2

C. 6

D. 14

Answer: B. 2

27. Which configuration would incorrectly represent Gd?

A. [Xe] 4f⁷ 5d¹ 6s²

B. [Xe] 4f⁸ 6s²

C. Both A and B are ground-state descriptions

D. None

Answer: B
The commonly expected Aufbau arrangement is not the actual ground-state configuration; Gd has [Xe] 4f⁷5d¹6s².

28. The stability of 4f⁷ is associated with:

A. Exchange energy

B. Pairing energy only

C. Zero nuclear charge

D. Absence of electrons

Answer: A. Exchange energy

29. Gadolinium is best classified as:

A. Alkali metal

B. Alkaline earth metal

C. Lanthanoid

D. Halogen

Answer: C. Lanthanoid

30. Which statement about Gd is correct?

A. It has a completely filled 4f subshell

B. It has a half-filled 4f⁷ subshell and one 5d electron

C. It belongs to the actinoid series

D. It has no unpaired electrons

Answer: B
Gadolinium has the exceptional ground-state configuration [Xe] 4f⁷5d¹6s².

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