Why are covalent network solids like diamond so hard?

In diamond, every carbon atom is bonded to four other carbons in a rigid 3D tetrahedral network of strong covalent bonds. There are no weak intermolecular forces, giving it extreme hardness and a high melting point.

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Core Study Guide

Non-Metals & Halogens

Properties and behaviors of non-metals.

Non-metals occupy the upper right section of the periodic table, characterized by high electronegativity and electron gain.

This unit covers properties of non-metals, the halogen group displacement reactions, and network covalent structures.

Key Takeaways

•Non-metals are poor conductors of heat and electricity due to localized electrons.
•Halogens (Group 17) exist as diatomic molecules and decrease in reactivity down the group.
•Noble gases (Group 18) are chemically inert.

Core Concepts & Definitions

1Properties of Non-Metals

Exist in various phases: solids (sulfur, carbon), liquid (bromine), and gases (nitrogen, oxygen).

•Brittle in solid state.

•Gain electrons to form negative anions in reactions.

Quick Revision Notes

•Non-metal oxides are acidic (e.g. CO2 forms carbonic acid in water).
•Halogen reactivity decreases down the group as atoms get larger and electron attraction weakens.