Metallic Bonding

Question 1

Which particles are free to move in metallic bonding?

Accepted Answer

Delocalised electrons — In a metal the outer electrons become delocalised and move freely; the positive ions stay fixed in the lattice.

Question 2

Metallic bonding is best described as the attraction between:

Accepted Answer

Positive ions and a sea of delocalised electrons — Metallic bonding is the electrostatic attraction between the lattice of positive ions and the delocalised electron sea.

Question 3

Why do metals conduct electricity?

Accepted Answer

Delocalised electrons carry charge through the metal — The free-moving delocalised electrons transport charge, so the metal conducts.

Question 4

Why are metals malleable?

Accepted Answer

Layers of ions slide while the electron sea keeps attracting them — Layers of positive ions can slide over each other; the delocalised electrons continue to hold the structure together, so it does not shatter.

Question 5

Which ion does a magnesium atom form in metallic magnesium?

Accepted Answer

Mg²⁺ — Magnesium loses its two outer electrons to form Mg²⁺, releasing two electrons into the electron sea.

Question 6

Why does magnesium have a higher melting point than sodium?

Accepted Answer

Mg²⁺ ions and more electrons give stronger attraction than Na⁺ — Mg²⁺ has a higher charge and contributes two electrons, giving a stronger electrostatic attraction, so more energy is needed to melt it.

Question 7

Metals generally have high melting points because:

Accepted Answer

Strong attraction between ions and electrons needs much energy to overcome — The strong metallic bond throughout the lattice requires large amounts of energy to break, giving high melting points.

Question 8

Why is an alloy usually harder than the pure metal?

Accepted Answer

Different-sized atoms stop the layers sliding easily — Atoms of a different size disrupt the regular layers, making it harder for them to slide, so the alloy is stronger and harder.

Question 9

In a metallic structure the positive ions are arranged in a:

Accepted Answer

Regular lattice — Metal ions form a regular, closely-packed lattice surrounded by delocalised electrons.

Question 10

Which property is NOT explained by delocalised electrons?

Accepted Answer

Low density of every metal — Delocalised electrons explain conduction and lustre, but density depends on ion mass and packing, and not all metals have low density (e.g. iron, gold are dense).

What is metallic bonding?

Explaining the properties