Q30 P - Chemistry: Molecular Nature Of Matter And Change

Question

Give the electron configuration of (a) La; (b) Ce³⁺ (c) Es; (d) U⁴⁺.

Step-by-Step Solution

Answer

(a) Electron configuration of 

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f⁰5d¹

(b) Electron configuration of 

1s²2d²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s¹

(c) Electron configuration of 

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f⁴5d¹⁰6p⁶7s²5f¹¹

(d) Electron configuration of 

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²

Step 1: Electron configuration

The electron configuration is 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, La has the atomic number of 57, therefore it has 57 electrons with electron configuration:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f⁰5d¹

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

 

(b) Based on the periodic table, Ce has the atomic number of 58, therefore it has 58 electrons.

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹5d¹

When it gains a charge of 3⁺, it loses 3 electrons, and will have only 55 electrons with electron configuration:

1s²2d²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s¹

 

(c) Based on the periodic table, Es has the atomic number of 99, therefore it has 99 electrons with electron configuration:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f⁴5d¹⁰6p⁶7s²5f¹¹

 

(d) Based on the periodic table, U has the atomic number of 92, therefore it has 92 electrons. 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²5f⁴

When it gains a charge of 4⁺, it loses 4 electrons, and will have only 88 electrons with electron configuration:

1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²4f¹⁴5d¹⁰6p⁶7s²