Question

Covalent radius of oxygen is \[0.74\text{A}{}^\circ \] and it’s A.R. electronegativity is 3.5. What is an effective nuclear charge experienced by oxygen? (Round-off to the nearest integer).

Answer 1

Hint: Allred and Rochow gave the relationship between electronegativity, effective nuclear charge and radius i.e $X\text{ = }\dfrac{O.359\text{ }{{\text{Z}}_{\text{eff}}}}{{{r}^{2}}}\text{ }+\text{ 0}\text{.744}$. Here, X is the electronegativity difference between two elements, ${{\text{Z}}_{\text{eff}}}$ is the effective nuclear charge and r is the radius of the atom.

Complete answer:
- In the given question, we have to find the effective nuclear charge that is experienced by the oxygen.
- As we know that the effective nuclear charge is the attractive force that is experienced by the outermost electron from the nucleus.
- Now, it is given that the value of the covalent radius is \[0.74\text{A}{}^\circ \] and A.R. electronegativity is 3.5. Here, A.R. is Allred-Rochow.
- Allred-Rochow gave the relationship between electronegativity, effective nuclear charge and atomic radius i.e
$X\text{ = }\dfrac{O.359\text{ }{{\text{Z}}_{\text{eff}}}}{{{r}^{2}}}\text{ }+\text{ 0}\text{.744}$
- So, by putting all the values in the above formula we can calculate the value of the effective nuclear charge.
$\text{3}\text{.5 = }\dfrac{O.359\text{ }{{\text{Z}}_{\text{eff}}}}{{{(0.74)}^{2}}}\text{ }+\text{ 0}\text{.744}$
$\text{3}\text{.5 - 0}\text{.744 = }\dfrac{O.359\text{ }{{\text{Z}}_{\text{eff}}}}{{{(0.74)}^{2}}}$
${{\text{Z}}_{\text{eff}}}\ =\text{ 4}\text{.2039}$
- So, the energy experienced by the outermost electron of the oxygen from the centre of the atom will be 4.2039.
- Moreover, as the atomic radius of an atom increases the distance between the centre and the outermost shell will increase due to which the value of effective nuclear charge will decrease.
Therefore, the effective nuclear charge experienced by the oxygen will be 4.2039.

Note:
According to Allred and Rochow, higher is the charge present on the surface of an atom the greater is the tendency of the atom to attract the outermost electron. There are many methods to calculate the electronegativity such as Pauling scale, Mulliken scale, etc.