3.) Account for each of the following in terms of principles of atom structure,

Question

3.) Account for each of the following in terms of principles of atom structure, including the number, properties, and arrangement of subatomic particles.

a.) the second Ionization energy of sodium is about three times greater than the second ionization energy of magnesium.

b.) The difference between the atomic radii of Na and K is relatively large compared to the difference between the atomic radii of Rb and Cs.

c.) A sample of Nickel Chloride is attracted to a magnetic field, whereas a sample of solid zinc chloride is not.

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Explanation / Answer

a) Atomic number of sodium = 11 (1s2,2s2p6,3p1)

For 1st ionization enthalpy (removel of 1st electron) = 1s2, 2s2p6 (Na+1)

For 2nd ionization enthalpy (removel of 2nd electron) = 1s2, 2s2p5 (Na+2)

Atomic number of magnesium = 12 (1s2,2s2p6,3p2)

For 1st ionization enthalpy (removel of 1st electron) = 1s2, 2s2p6, 3p1(Mg+1)

For 2nd ionization enthalpy (removel of 2nd electron) = 1s2, 2s2p6 (Mg+2)

Valence shell configuration 2s2p6 (for Mg+2) is most stable and preferred configuration. In this case magnesium has complete octat and also the configuration of Neon (1s2, 2s2p6), which is an inert gas.

Second ionization energy of sodium is: 4560 kj/mol

Second ionization energy of magnesium : 1450 kj/mol

Sodium becomes stable after first ionization (complete octat), but magnesium becomes stable after 2nd ionization. Hence, 2nd ionization energy of sodium is about three times more tham second ionization energy of magnesium.

b) Electronic configurations of Na, K, Rb, Cs are:

Na11 = 1s2, 2s2p6, 3s1 (no d electron) (atomic radii = 154 pm)

K19 = 1s2, 2s2p6, 3s2p6, 4s1 (no d electron) (atomic radii = 196 pm)

Rb37 = 1s2, 2s2p6, 3s2p6, 4s2, 3d10, 4p6, 5s1 (d electrons are present= 10) (atomic radii = 211pm)

Cs55 = 1s2, 2s2p6, 3s2p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s1 (d electrons are present= 20) (atomic radii = 225pm)

Presence of d-electron decreases the attraction between nucleus and valence shell, which increases the atomic radii and atom becomes larger in size.

c) Electronic configuration of nickle (atomic no 28) = 1s2, 2s2p6, 3s2p6, 4s2, 3d8

   Electronic configuration of zinc (atomic no 30) = 1s2, 2s2p6, 3s2p6, 4s2, 3d10

Nickle has 2 unpaired electrons, hence it is attracted to magnetic field (paramagnetic).

zinc has no unpaired electron (filled d-orbital), hence it is not attracted to magnetic field (dimagnetic).

For attraction in the magnetic field, atleast one unpaired electron should be present.

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