181.

What is the basic difference between the terms electron gain enthalpy and electronegativity?

The first  and the second  ionization enthalpies (in  kJ mol^-1) and the  electron gain enthalpy (in kJ mol^-1) of a few elements are given below:
Elements                                            
I                        520                    7300                    -60
II                       419                     3051                   -48
III                      1681                    3374                  -328
IV                       1008                    1846                 -295
V                         2372                    5251                 +48
VI                        738                      1451                -40  
Which of the above elements is likely to be:
(a) the least reactive element.
(b) the most reactive metal.
(c) the most reactive non-metal.
(d) the least reactive non-metal.
(e) the metal which can form a stable binary halide of the formula MX₂(X =halogen).
(f) the metal which can form a predominantly stable covalent halide of the formula MX(X= halogen)?

The plot of square root of frequency of X-ray emitted against atomic number led to suggestion of which law/rule?

• Periodic law

• Modern periodic law

• Hund's rule

• Newland's law

Which of the following atoms has the highest first ionisation energy?

• Na

• K

• Sc

• Sc

Which of the following represents the correct order of increasing first ionisation enthalpy for Ca, Ba, S, Se and Ar?

• Ca <S<Ba<Se<Ar

• S< Se<Ca<Ba< Ar

• Ba< Ca<Se< S< Ar

• Ba< Ca<Se< S< Ar

The first ionisation potential of Na is 5.1 eV. The value of electron gain enthalpy of Na⁺ will be

• -2.55 eV

• -5.1 eV

• -10.2 eV

• -10.2 eV

The increasing order of the ionic radii of the given isoelectronic species is 

• Cl-, Ca²⁺, K⁺, S^2-

• S^2-, Cl^-, Ca²⁺,K⁺

• Ca²⁺, K⁺, Cl^-, S^2-

• Ca²⁺, K⁺, Cl^-, S^2-

The outer electron configuration of Gd (Atomic No : 64) is

• 4f³ 5d⁵ 6s²

• 4f⁸ 5d⁰ 6s²

• 4f⁴ 5d⁴ 6s²

• 4f⁴ 5d⁴ 6s²

The correct sequence which shows decreasing order of the ionic radii of the elements is

• Al³⁺ > Mg²⁺ > Na⁺ > F^- > O^2-

• Na⁺ > Mg²⁺ > Al³⁺ > O^2- > F^-

• Na⁺ > F^- > Mg²⁺ > O^2- > Al³⁺

• Na⁺ > F^- > Mg²⁺ > O^2- > Al³⁺

The set representing the correct order of ionic radius is

• Li⁺> Be²⁺> Na⁺> Mg²⁺

• Na⁺>Li⁺>Mg²⁺> Be²⁺

• Li⁺>Na⁺ > Mg²⁺ > Be²⁺

• Li⁺>Na⁺ > Mg²⁺ > Be²⁺