Give reason-`Na^(23)` and `Na^(24)` show the similar chemical proper- ties.

Li and Mg are found in different groups of the periodic table, yet they show similar chemical properties. Explain.

Although zirconium belongs to 4d transition series and hafnium to 5d transition series even then they show similar physical and chemical properties because -

A hydrocarbon (X) discharges the colour of cold alkaline KMnO_4 solution and reacts with warm dilute sulphuric acid containing HgSO_4 to form another compound (Y). (Y) gives positive iodoform test but does not react with Tollens' reagent. (Y), when distilled with 80% H_2SO_4 , gives sym-trimethylbenzene. Identify the compounds (X) and (Y) and write the reactions involved with proper reasons.

What are representative elements? Give the reason for their chemical reactivity?

X-ray diffraction studies show that edge length of a unit cell of NaCl is 0.56 nm. Density of NaCl was found to be 2.16g//"cc". What type of defect is found in the solid? Calculate the percentage of Na^(+) and Cl^(-) ions that are missing.

Examine whether the follwing sentences are statements or not . Give reasons for your answers . x^(2)-11|x|+24=0 has four real roots .

Give a comparative study of the structures of diamond and graphite. Explain with proper reason.

Why are sodium (Na) and potassium (K) placed in the same group of the pariodic table? Give any two reaons?

Give reason : Sc^(3+) is colourless in aqueous solution whereas Ti^(3+) is coloured.