Why were the names eka-aluminium and eka-silicon given to gallium and germanium by Mendeleev?

Why do elements in the same group have similar physical and chemical properties?

A boy has reported the radii of Cu,Cu⁺ and Cu²⁺ as 0.096 nm,0.122 nm and 0.072 nm respectively.However, it has been noticed that he interchanged the values by mistake. Assign the correct values to different species.

Four elements have the following first ionisation enthalpies ( in kJ mol^-1); 869, 941, 1191 and 1142. The elements, in random order, are Se, Br, Te and I. Which element has an ionisation enthalphy of 869 kJ mol^-1 and 1142 kJmol^-1 respectively?

Explain why chlorine can be converted into chloride ion more easily as compared to fluoride ion from fluorine.

Electronegativity of F on Pauling scale is 4.0. What is the value on Mulliken's scale.

All transition elements are d-block elements, but all d-block elements are not transition elements. Explain.

How many elements can be accommodated in the present set up of the long form of the periodic table? Explain.

The amount of energy released when 1\(\times \)10¹⁰  atoms of chlorine in vapor state are converted to Cl^- ions according to the equation, Cl ( g ) +  e^- \(\longrightarrow\) Cl^- ( g ) is 57.86 \(\times\)10^-10 J
Calculate the electron gain enthalpy of the chlorine atom in terms of kJ mol^-1 and eV per atom.

Arrange the following as stated. 'Decreasing order of electropositive character of Cu, Fe Mg'

How does the metallic and non-metallic character vary on moving from left to right in a period?

The elements Z = 117 and 120 have not yet been discovered. In which family/group would you place these elements and also give the electronic configuration in each case.