Metallic bonding

The diagram below shows part of a giant metallic structure.

a. Use this diagram to explain the main features of metallic bonding.

b. Explain why metals are good conductors of electricity.

c. Explain why, in general, metals have high melting points.

a. Metallic bonding is strong. This is because the ions are held together by the strong electrostatic attraction between their positive charges and the negative charges of the delocalised electrons.

This electrostatic attraction acts in all directions. The strength of metallic bonding increases with: 

• increasing positive charge on the ions in the metal lattice 
• decreasing size of metal ions in the lattice
• increasing number of mobile electrons per atom.

b. When a voltage is applied to a piece of metal, an electric current flows in it because the delocalised electrons (mobile electrons) are free to move, leading to metal being good conductors of electricity

c. It takes a lot of energy to weaken the strong attractive forces between the metal ions and the delocalised electrons. These attractive forces can only be overcome at high temperatures.

Explain why molten sodium iodide conducts electricity but molten iodine does not.

In contrast, sodium ions (Na⁺) and iodide ions (I⁻) combine to generate sodium iodide, an ionic molecule. When sodium iodide is solid, it creates a crystalline lattice in which the ions are fixed and unable to move freely. Solid sodium iodide does not conduct electricity because of this fixed location. On the other hand, conductivity is made possible when the ions are melted since the ionic bonds are broken. Whereas molten iodine does not because it does not have any free electrons which is required for electricity to flow through it.

Explain why magnesium has a considerably higher boiling point than sodium.

Magnesium forms an Mg²⁺ ion and sodium forms an Na⁺ ion. That leads the electrostatic forces of attraction in magnesium to be stronger than that of sodium. As a result, this will be required more energy to break the attraction in magnesium than sodium.

State two factors that affect the strength of metallic bonding in metals.

• The number of valence electrons in the metal atoms
• The size of the metal ions
• The arrangement of atoms in the metallic lattice

Which of the following materials only contain one type of bond in solid form?

A. Ammonium chloride

B. Brass (an alloy of zinc and copper)

C. Ice

D. Iodine crystals

The answer is B.

Metallic bonding is formed when the ions are held together by the strong electrostatic attraction between their positive charges and the negative charges of the delocalised electrons. in Brass both atoms present are metals and will undergo the same type of bonding with each other.

A is incorrect because ammonium chloride haves covalent bonds and ionic bonds

C is incorrect because ice has covalent and hydrogen bonds

D is incorrect because iodine has covalent bonds and dipole forces between molecules

Why can copper conduct electricity?

A. Positive ions can move through the structure

B. Delocalised electrons can move through the structure

C. There is an electrostatic attraction between positive ions and delocalised electrons

D. The layers of ions can slide over each other

The answer is B.

When a voltage is applied to a piece of metal, an electric current flows in it because the delocalised electrons (mobile electrons) are free to move, leading to metal being good conductors of electricity.

A is incorrect because the delocalised electrons move instead

C is incorrect because this is a description of a metallic bond

D is incorrect because this is a property of malleability of a metal

Which factor contributes to the high thermal conductivity of metals? 

A. strong covalent bonds

B. weak metallic bonds

C. free movement of electrons

D. presence of ions

The answer is C.

The conduction of heat is partly due to the movement of the delocalised electrons and partly due to the vibrations passed on from one metal ion to the next.

A is incorrect because metals do not have covalent bonds

B is incorrect because metallic bonds are strong

D is incorrect because the presence of ions is not related to the thermal conductivity

Metallic bonding contributes to which of the following properties of metals? 

A. malleability and ductility

B. brittle nature 

C. low electrical conductivity

D. low melting and boiling points

The answer is A.

B is incorrect because metals are not brittle

C is incorrect because metals have high electrical conductivity

D is incorrect because more energy is required to break the attraction in metal, leading to have high meting and boiling points

Which one of the following is not true of metallic bonding? 

A. It gives rise to excellent electrical conductivity. 

B. Electrons are free to move throughout the structure. 

C. The strength of metallic bonds increases down a group. 

D. The strength of metallic bonding affects the boiling point of metal.

The answer is C.

A is correct because the delocalized electrons in metallic bonds are free to move, allowing metals to conduct electricity efficiently

B is correct because electrons are free to move throughout the structure and can flow freely, 

C is incorrect because the strength of metallic bonds increases down a group

D is correct because stronger metallic bonds lead to higher boiling points due to the additional energy required to break these bonds during the phase change from liquid to gas

Which of the following metals will have the greatest ability to conduct electricity?

A. Li

B. Mg

C. Na

D. Al

The answer is D.

When a voltage is applied to a piece of metal, an electric current flows in it because the delocalised electrons (mobile electrons) are free to move, leading to metal being good conductors of electricity. Thus, the number of valence electrons increases, the number of delocolised electrons increases as well.

Al has 3 valence electrons

Mg has 2 valence electrons

Li and Na have 1 valence electron