Question

(i) The unpaired electrons in Al and Si are present in 3p orbital. Which electrons will experience more effective nuclear charge from the nucleus? 

(ii) Indicate the number of unpaired electrons in: (a) P, (b) Si, (c) Cr, (d) Fe 

Answer 1

(i) the electrons in the 3p orbital of silicon will experience a more effective nuclear charge than aluminium. 

(ii) (a) Phosphorus (P): Atomic number = 15 The electronic configuration of P is: 1s² 2s² 2p⁶ 3s² 3p³ 

The orbital picture of P can be represented as: 

From the orbital picture, phosphorus has three unpaired electrons. 

(b) Silicon (Si): Atomic number = 14

The electronic configuration of Si is: 1s² 2s² 2p⁶ 3s² 3p² 

The orbital picture of Si can be represented as:

From the orbital picture, silicon has two unpaired electrons. 

(c) Chromium (Cr): Atomic number = 24

The electronic configuration of Cr is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵ 

The orbital picture of chromium is:

From the orbital picture, chromium has six unpaired electrons. 

(d) Iron (Fe): Atomic number = 26 

The electronic configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶ 

The orbital picture of chromium is:

From the orbital picture, iron has four unpaired electrons.