The increasing order of the first ionisation enthalpies of the elements B, P, S and F is
B < S < P < F
F < S < P < B
P < S < B < F
B < P < S < F
A.
B < S < P < F
In general,
(i) First ionisation energy (IE1) or enthalpy increases along the period from left to right but due to half-filled configuration of P-atom, it has higher IE1 than of S-atom.
(ii) IE1 decreases as we move down the group from top to bttom.
(iii) More be the size of atom, less be the IE1.
Hence, the correct order of IE1 is B < S < P < F.
The equation used to represents the electron gain enthalpy is
X(g) + e- → X-(g)
X(s) + e- → X-(g)
X(g) → X+(g) + e-
X(s) → X+(g) + e-
The electronic configuration of Eu (Atomic no.63), Gd (Atomic no. 64) and Tb (Atomic no. 65) are
[Xe]4f6 5d1 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2
[Xe] 4f6 5d1 6s2 , [Xe] 4f7 5d1 6s2 and [Xe] 4f8 5d1 6s2
[Xe] 4f7 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2
[Xe] 4f7 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2
An element in +2 oxidation state has 24 electrons. The atomic number of the element and the number of unpaired electrons in it respectively are
24 and 4
26 and 4
24 and 2
26 and 5
The element having greatest difference between its first and second ionization energies, is
K
Ca
Ba
Sc
Among the following, the isoelectronic specie (s) is/are
(i) O2-, F-, Na+, Mg2+
(ii) Na+, Mg+, Al3+, F-
(iii) N3-, O2-, F-, Ne
(i) and (ii)
(i), (ii) and (iii)
(ii) and (iii)
(i) and (iii)
The electronic configuration of 59Pr ( praseodimium) is
[54Xe] 4f25d16s2
[54Xe] 4f15d16s2
[54Xe] 4f36s2
[54Xe] 4f35d2
The size of the iso-electronic species Cl-, Ar and Ca2+ is affected by:
nuclear charge
Prinicpal quantum number of valence shell
azimuthal quantum number of valence shell
electron-electron interaction in the outer orbitals