21. Why manyproperties of berylliumresemble aluminum, and boron resemblesilicon? This is due to

A.amphoteric property

C. allotropic relationship

B. diagonal relationship D. Isoelectronic

22. Which one of the following compoundsis called milk of magnesia?

A.MgOC. MgSO_{4}

B.Mg (OH) 2 D . MgCl_{2}

23. Which one of the following molecules cannot react with carbon atom?

A. H_{2}B S_{8}

C. N_{2} and O_{2}

D. None of the above

24. Which one of the following represents superoxide of rubidium?

A. Rb_{2}O

B. Rb_{2}O_{2}

C. RbO_{2}

D. RbO

25. Which one of the following metals does not form peroxide or superoxide?

A. Li

B. Na

C. Rb

D.Cs

The resemblance of beryllium to aluminum and boron to silicon is explained by the diagonal relationship. Elements that are diagonally positioned to each other in the periodic table often share similar chemical properties.

22. **Answer: B. Mg(OH)₂**

Milk of magnesia is magnesium hydroxide (Mg(OH)₂).

23. **Answer: C. N₂ and O₂**

Nitrogen (N₂) and oxygen (O₂) molecules are diatomic and do not react directly with carbon atoms.

24. **Answer: C. RbO₂**

The superoxide of rubidium is represented as RbO₂.

25. **Answer: A. Li**

Lithium (Li) does not form peroxide or superoxide. Sodium (Na), rubidium (Rb), and cesium (Cs) can form peroxides or superoxides.