s- and p-Block Elements — Part 2: Groups 13 and 14: visual lesson, CBSE Class 11 Chemistry

Lesson

Groups 13 and 14: boron and carbon families

Part 2 — the p-block elements B, Al, Ga, In, Tl and C, Si, Ge, Sn, Pb. As in Part 1, this chapter is formative assessment only and is taught at textbook depth for school tests.

In this lesson you will

Describe the trends in radius, ionisation enthalpy and electronegativity in groups 13 and 14 and explain the irregularities
Explain the inert pair effect and the oxidation states of the heavier elements
Explain the anomalous behaviour of boron and carbon, and the catenation of carbon
Describe diamond, graphite and fullerene at a general level

Table of some elements of groups 13 and 14 with valence configuration and uses
Element	Group	Valence configuration	Where you meet it
Boron	13	2s² 2p¹	Borax, glass
Aluminium	13	3s² 3p¹	Foil, cooking vessels
Carbon	14	2s² 2p²	Diamond, graphite, all organic compounds
Silicon	14	3s² 3p²	Sand, chips
Lead	14	6s² 6p²	Batteries

Concept

Group 13: configuration and data

Valence configuration ns² np¹. The metallic character increases from B (a metalloid) to Tl, but the data are irregular because of the poor shielding by inner d electrons from Ga onwards.

Table of atomic radius, M three plus radius, first ionisation enthalpy and electronegativity for boron to thallium
Element	B	Al	Ga	In	Tl
Atomic radius / pm	85	143	135	167	170
M³⁺ radius / pm	27	53.5	62	80	88.5
IE₁ / kJ mol⁻¹	801	577	579	558	589
Electronegativity	2.0	1.5	1.6	1.7	1.8

Diagram

Group 13 trends as plots

Group 13 breaks the smooth trend: gallium is smaller than aluminium and the ionisation enthalpies are irregular.

Unlike group 1, Ga < Al in size, and IE₁ rises again at Ga and at Tl. Cause: the ten 3d electrons (and, for Tl, the 4f electrons) shield the extra nuclear charge poorly.

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