Q10.1P - Chemistry: Molecular Nature Of Matter And Change

Question

Which of these atoms cannot serve as a central atom in a Lewis structure?

1. O;
2. He;
3. F;
4. H; 
5. P?

Explain.

Step-by-Step Solution

Answer

In the Lewis structure,

 

1. O can serve as a central atom.
2. He cannot serve as a central atom.
3. F cannot serve as a central atom.
4. H cannot serve as a central atom.
5. P can serve as a central atom.

Step 1: Lewis Structure

A Lewis structure can be defined as the basic structure of a molecule which used the valence electron of each atom involved.

In the Lewis structure, the least electronegative atom will be the central atom.

Step 2: Subpart (a) Explanation for Oxygen.

Oxygen belongs to Group 16 of the periodic table. The noble gas configuration can be achieved by O-atom after accepting two electrons as it has 6 electrons in the valence shell. Hence, it can bond to two other atoms.

Thus, oxygen can serve as a central atom in the Lewis structure.

Step 3: Subpart (b) Clarification for Helium.

Helium belongs to Group 18 of the periodic table. Helium cannot serve as a central atom in Lewis’s structure as it has only two valence electrons.

It is a noble gas and doesn’t require bonding for completing octet, to get stabilized configuration.

Step 4: Subpart (c) Simplification for Florine atom.

The fluorine atom has 7 electrons in the valence shell as it belongs to the Group 17 of the periodic table.

There are no d-orbitals to extend the valence shell. Therefore, it can only be bonded to one other atom.

Thus, it cannot act as a central atom in the Lewis structure.

Step 5: Subpart (d) Description of the Hydrogen atom.

Hydrogen cannot function as the central atom of the Lewis structure. It has only one electron in the valence shell, so it can bond to only one atom.

 

Step 6: Subpart (e) Interpretation for Phosphorus.

Phosphorus is a Group 15 element; it has 5 valence electrons. It needs three more electrons to have eight electrons in its valence level; it has vacant d-orbitals to expand its valence level.

It can bond to three other atoms. Therefore, it can function as the central atom of the Lewis structure.