What are the properties of the atom?

What are the properties of the atom?

Aug 26, 2022, 16:45 IST

Atomic Properties:

1) Electronic configuration:

The elements of group IVA or 14 have a general configuration of ns ² np ² with a total of 4 electrons in their valence shell.

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2) Atomic Radii:

Atomic radii increase from carbon to lead. The increase from carbon to silicon is abnormally high followed by a continuous small increase as usual.

Their radii are smaller in comparison to the corresponding group 13 elements.

Increase in the size down the group is due to addition of a new shell with every new period. The decrease in comparison to group 13 is accounted for the increase in the effective nuclear charge.

• The abnormal increase from C to Si is due to presence of 8 penultimate, which produce greater shielding and thereby comparatively less attraction of the nucleus.

3) Ionization Enthalpy:

The first ionization enthalpy of group 14 decreases down the group from carbon to silicon. The decrease is much pronounced from carbon to silicon thereafter it decreases upto Sn followed by a slight increase for Pb.

The values of I.E., are greater than that of group 13.

On moving down, size increases and the screening effect of inner electrons decrease. However, the over all effect is that the electron can be pulled off more easily. The increased value of IE of Pb in comp. to Sn is due to poor shielding of 4f electrons making a slightly tightly bound e ^- which need just a bit more energy to pull them off.

The values for 2 ^nd , 3 ^rd and 4 ^th I.E. are even higher and correspond to the order:

IE ₁ < IE ₂ < IE ₃ < IE ₄

The reason behind increasing value of IE is the increasing charge on atom from IE ₂ to IE ₄ which attracts the electron with more strength towards them (coulomb attraction); hence more energy will be required.

4) Electronegativity:

Electronegativity decreases from carbon to lead because of increasing size. Carbon has comparatively higher value i.e., 2.5; the rest have almost same value with very little decrease for further elements.

Small sized carbon has a control over its valence e ^- and can attract further e ^- to complete its octet. The capacity to attract an electron decreases down due to increasing size and shielding effect, which in turn gets almost forfeited by increasing nuclear charge.

The value, is however greater than group 13 for the first 3 elements and almost equal for the last 2. The increase for the first three elements is due to smaller size and increasing nuclear charge, but this charge becomes very less effective when size increases. So the nucleus can attract an e ^- almost same extent.

5) Density: Initially there is gradual increase C _graphite to Si followed by rapid increase for higher members.

6) MP & BP: The mp and bp of this group are higher than group 13 and decrease down the group with only exception observed in mp of Pb (600 ⁰ K) which is higher than that of Sn (503).

The much higher values of mp & bp for C and Si are based on their strongly covalent network structure. Considerable decrease after germanium is due to weak metal-metal or metallic bonds.

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