Question

"Middle row anomaly" is related with: This question has multiple correct options
A. Stability of transition metal oxides
B. Stability of alkali metal oxides
C. Instability of halogen oxides
D. Stability of alkaline earth metal oxides

Answer 1

Hint: In the periodic table of the elements the phase middle row anomaly refers to the relative instability of bromide oxides. This concept helps us to answer the question.

Complete step-by-step answer:
The bromide ions are the least stable halogen oxide as compared to the chloride ions and iodine and exist only at low temperature due to transition metal contraction.
The cause behind the middle row anomaly is because all 10 electrons in the bromine atom’s third orbital that is 3d are comparatively close to the nuclear and exert comparatively less repulsion on the five electrons in its fourth orbital 4p.
Therefore the bonds between bromine and oxygen’s outer orbital are easier to break, rendering the bromine oxides quite powerful as oxidising agents.

The force which is equal to increased effective nuclear charge till Cobalt so that size remains same but after Nickel this repulsion exceeds then increase in effective nuclear charge due to increase in electrons subshell which results in increase in size. This is known as transitional contraction.

By transition metal oxides we mean the compounds which are composed of oxygen atoms bound to transition metals.

So we can say that the middle low anomaly is related to the stability of transition metal oxides and instability of halogen oxides.
Therefore, the correct options are Option A and Option C.

Note: We should know that because of the mentioned reasoning one might assume the astatine oxides to be similarly unstable, the anomaly has more to do with the shielding effect of the transition orbital than the location of the element in the middle row of the periodic table.