Question

Explain why the decrease in atomic radius from sodium to chloride is greater than that from
scandium to copper

Answer 1

Atomic radius is inversely proportional to the effective nuclear charge. As we move from left to right in a period the effective nuclear charge increases. This decreases the radius of an atom. At the same time, in transition elements the number of electrons in the 3d sub-shell will increase. This will repel the already present 4s electrons and will increase the atomic radius. In Fe, Co, Ni & Cu both the effects nearly balance each other keeping the atomic radius same.

Answer 2

Let us answer it

Explanation:

Atomic radii

It is the distance of outermost shell from center of nucleus .

Along group : General trend

It increases : Because as we move down every time a new shell is being added  due to which nuclear charge increases and size decreases .

Along Period : General trend

It decreases : Because every time we move in period , a new electron is added to the same shell  due to which nuclear charge increases and size decreases .

This general trend is observed as we move in a period from Na to Cl as electronic configurations for both are :

Na ---------------------------------------Cl

2,8,1                                             2,8,7

But this decrease is not much seen when we move from Sc to Cu .

The reason being : As we move from Sc to Cu , the filling of d orbital occurs that show screening effect .

Now let us understand about screening or shielding effect

The property of certain orbitals that do not allow the actual nuclear charge to reach till end of atomic shell because of their shape .As a result the outer electrons do not experience  nuclear charge , they experience effective nuclear charge which is less than the actual nuclear charge .