Topic 4.5: Metallic bonding

Question 1

Definition of metallic bond

Answer 1

Electrostatic attraction between the positive metal ions in a lattice and the delocalized electrons

Question 2

Definition of delocalized electrons

Answer 2

E- that do not belong to any atom but are able to move throughout the structure

Question 3

Factors that affect the strength of metallic bond

Answer 3

a) Charge of the ions
b) Radius of the metal ion
c) # of delocalized e-

Question 4

Strength of metallic and charge of the ions

Answer 4

Mg forms a 2+ ion and Na forms a 1+ ion. Then, the electrostatic attraction between the ions and the delocalized electrons is stronger in Mg

Question 5

Strength of metallic bond and radius of the metal ion

Answer 5

Mg+2 ion is smaller than Na+ ion. Then, the delocalized electrons are closer to the nucleus and more strongly attracted.

Question 6

Strength of metallic and # delocalized electrons

Answer 6

There are one and two delocalized electrons per atom respectively in Na and Mg. Then, there will be stronger electrostatic attractions between the ions and the delocalized electrons in Mg.

Question 7

Properties of metals

Answer 7

a) Good electrical conductivity
b) Malleable, can be shaped under pressure
c) Ductile, can be drawn out into threads
d) High melting points

Question 8

Explanation of the good electrical conductivity of metals

Answer 8

Delocalized electrons are highly mobile, so they can move through the metal structure in response to an applied voltage.

Question 9

Explanation of the malleability and ductility of metals

Answer 9

The closed-packed layers of cations can slide over each other without breaking more bonds that are formed.

Question 10

Explanation of the melting point of metals

Answer 10

A lot of energy is required to break the strong metallic bonds and separate the atoms.

Question 11

Explanation of the exception of the trends of melting points in metals

Answer 11

Sn and Pb due to the way in which their ions are packed

Question 12

Definition of alloys

Answer 12

Solid solutions containing more than one metal and held together by metallic bonding

Question 13

How is it possible the production of alloys?

Answer 13

Due to the non-directional nature of delocalized e-, and the fact that a lattice can accommodate ions of different size

Question 14

Enhanced properties of alloys

Answer 14

Greater strength

Question 15

Explanation of the enhanced properties of alloys

Answer 15

a) Since the added metal has a different radius, it distort the lattice structure of the metal making the bonding less directional
b) The distorted lattice prevents the layers to slide over each other

Question 16

Examples of alloys

Answer 16

a) Brass (Cu + Zn)
b) Steel (Fe + C)
c) Bronze (Cu + Sn)