Q31 P - Chemistry: Molecular Nature Of Matter And Change

Question

Give the electron configuration of (a) Pm  (b) Lu³⁺ (c) Th  (d) Fm³⁺

Step-by-Step Solution

Answer

(a) Electron configuration of Pm 

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f⁵

(b) Electron configuration of Lu³⁺ 

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹²

(c) Electron configuration of Th 

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f²

(d) Electron configuration of Fm³⁺

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f⁹

Step 1: Electron configuration

The electron configuration is that the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals.

Step 2: Electron configuration of each elements.

(a) Based on the periodic table, Pm has the atomic number of  61, therefore it has 61 electrons with electron configuration:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f⁵

Instead of being in the 4f orbital, the lone electron went to the d-orbital.

 

(b) Based on the periodic table, Lu has the atomic number of 71, therefore it has 71 electrons.

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹

When it gains a charge of 3⁺, it loses 3 electrons, and will have only 68 electrons with electron configuration:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹²

 

(c) Based on the periodic table, Th has the atomic number of 90, therefore it has 90 electrons with electron configuration:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f²

 

(d) Based on the periodic table, Fe has the atomic number of 100, therefore it has 100 electrons.

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f¹²

When it gains a charge of 3⁺, it loses 3 electrons, and will have only 88 electrons with electron configuration:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f⁹