Lecture 5

Question 1

Describe metallic bond

Answer 1

Packed closely together
Regular arrangement (lattice).
Lose their outer shell electrons and become positive ions.
free to move throughout the metal lattice.

Question 2

What are delocalized electrons?

Answer 2

Delocalized electrons are electrons that are not associated with any one particular atom or bond.

Question 3

Why are metallic bonds strong?

Answer 3

This is because the ions are held together by the strong electrostatic attraction between their positive charges and negative charges of the delocalised electrons. The electrostatic attraction acts in all directions.

Question 4

When does the strength of metallic bonding increase?

Answer 4

Increasing positive charge on the ions in the metal lattice and decreasing size of metal ions in the lattice.

Question 5

Why does sodium have a low melting point and why is it soft?

Answer 5

Can be explained by the relatively low number of electrons in the electron sea and the relatively small charge on the sodium cation.

Question 6

Why is the melting point of magnesium significantly higher than that of sodium?

Answer 6

Due to the greater magnitude of charge and the greater electron density in the sea.

Question 7

What are the key properties of metal?

Answer 7

High melting point, malleable, ductile, good conductors heat/electricity

Question 8

Why do metals have high melting points?

Answer 8

It takes a lot of heat energy to break up the lattice, with its strong metallic bonds.

Question 9

Why are metals malleable and ductile?

Answer 9

This is because the layers can slide over each other.

Question 10

Why are metals good conductors of heat?

Answer 10

The free electrons take in heat energy, which makes them move faster . They quickly transfer the heat through the metal structure.

Question 11

Why are metals good conductors of electricity?

Answer 11

The free electrons can move through the lattice carrying charge. Silver is the best conductor.

Question 12

Would you expect molten metals to conduct?

Answer 12

Yes, metals conduct electricity in their molten state. They form cations by losing electrons and these electrons are responsible for conducting electricity so efficiently.

Question 13

Why can metals be drawn out into wires without breaking?

Answer 13

Ductility is the property of metals that enable metals to be drawn into thin wires.

Question 14

What has the strongest type of intermolecular force?

Answer 14

Hydrogen bonding

Question 15

When is a hydrogen bond highly polarised?

Answer 15

When a hydrogen atom is covalently bonded to a very electronegative atom, the bond is very highly polarized.

Question 16

What angle gives a hydrogen bond its maximum strength?

Answer 16

The angle between the covalent bond to the hydrogen atom and the hydrogen bond is usually 180 degrees.

Question 17

What is hydrogen bond of water?

Answer 17

Water has two hydrogen atoms and two lone pairs per molecule.

Question 18

What are the properties of hydrogen bonds?

Answer 18

Soluble in water, less volatile and higher viscosity/ high surface tension

Question 19

What is an intramolecular hydrogen bond?

Answer 19

Hydrogen bonding which takes place within a molecule itself. It takes place in compounds containing two groups such that one group contains hydrogen atom linked to an electronegative atom and the other group contains a highly electronegative atom linked to a lesser electronegative atom of the other group.

Question 20

What is intermolecular hydrogen bonding?

Answer 20

When hydrogen bonding takes place between different molecules of the same or different compounds.

Question 21

What is the difference between covalent bonds and hydrogen bonds?

Answer 21

1. Covalent bonds are formed by sharing of electrons between the atoms. Hydrogen bonds are they type of attractive forces that is present between the two different molecules.
2. Covalent bonds formed are the interatomic bonds. Hydrogen bonds can be intramolecular or intermolecular.
3. Covalent bonds are formed in between two atoms. Hydrogen bonds are formed between two or more atoms of same or different molecules.

Question 22

How do you rank the strength of the hydrogen bonds between HF, H20 and NH3?

Answer 22

The extent of hydrogen bonding depends upon electronegativity and the number of hydrogen atoms available. HF>H2O>NH3.

Question 23

How do you find electronegativity on the periodic table?

Answer 23

Electronegativity increases from bottom to top in groups, and increases from left to right across periods.