Atomic theory 8

Question 1

Define electronegativity (L.C)

Answer 1

The relative power of attraction an atom of an element has for the shared pair of electrons in a covalent bond.

Question 2

Why is there an increase in electronegativity value moving from gallium to germanium in the periodic table? (L.C)

Answer 2

• Nuclear charge increasing

- Atomic radius decreasing

Question 3

Mendeleev predicted the properties of the elements gallium and germanium years before either of them discovered. Explain the basis for his predictions. (L.C)

Answer 3

Predicted the properties of known elements

Question 4

Write the molecular formula for the simplest compound formed between germanium and hydrogen. (L.C)

Answer 4

GeH₄

Question 5

Would you expect GeH₄ to be water soluble? Justify your answer. (L.C)

Answer 5

• No

- GeH₄ is a non-polar solute

Question 6

Define electronegativity (L.C)

Answer 6

The relative power of attraction an atom of an element has for the shared pair of electrons in a covalent bond.

Question 7

State and explain the trend in electronegativity values down the first group in the periodic table of elements. (L.C)

Answer 7

• Decrease

- Increasing atomic radius and increased screening offsets increased nuclear charge

Question 8

Use electronegativity values to predict the types of bonding (i) in water, (ii) in methane, (iii) in magnesium chloride. (L.C)

Answer 8

Water - polar covalent
Methane - covalent
Magnesium chloride - ionic

Question 9

Use your knowledge of intermolecular forces to explain why methane has a very low boiling point. (L.C)

Answer 9

Very weak intermolecular forces.

Question 10

The relative molecular mass of methane is only slightly lower than that of water but the boiling point of water is much higher. Suggest a reason for this (L.C)

Answer 10

Much stronger hydrogen bonds between water molecules.