Question

Diagonal relationships in the periodic table exist as well as vertical relationships. For example, Be and Al are similar in some of their properties, as are B and Si. Rationalize why these diagonal relationships hold for properties such as size ionization energy, and electron affinity.

Short answer

Answer

The similarity in properties observed between two elements placed diagonally from left to right in two adjacent groups in the periodic table is known as a diagonal relationship. The pair of elements with a diagonal relationship exhibit similar chemical properties.

Step-by-step solution

Step1:

(Discussing about the diagonal relationship between elements on the basis of atomic radii as a periodic trend)

Since atomic radius decreases along a period from left to right and increases down a group in the periodic table of elements.

For example, let us consider the element Be. If we move one element to the right and one element down, we get Al. Considering the trend of atomic radius, we can state that diagonal pairs result in similar atomic radii.

Step 2:

(Discussing about the diagonal relationship between elements on the basis of ionization energy and electron affinity as periodic properties)

Since the ionization energy trend opposes the atomic radius trend, it results in similar ionization energies in diagonal pairs. Since electron affinity has a general trend, although quite a few exceptions, we can state that elements with similar atomic radii and ionization energies have similar electron affinities as well.