2012 Atoms, Bonds and Groups Jun

Question 1

Define relative atomic mass

Answer 1

• The (weighted) mean mass of an atom (of an element
• compared with 1/12th (the mass)
• of (one atom of) carbon-12

Question 2

Describe how induced dipoles arise

Answer 2

• Uneven distribution of electrons
• Creates or causes an instantaneous dipole OR temporary dipole (in a molecule)
• Causes induced dipoles in neighbouring molecules

Question 3

Suggest why there are no other intermolecular forces in solid sulfur

Answer 3

• Only one type of atom

* No (permanent) dipoles OR non-polar OR no polar bonds

Question 4

What does the term anhydrous mean

Answer 4

• There are no waters of crystallisation

Question 5

Explain why a molecule of SF6 has an octahedral shape

Answer 5

• Sulfur has six bonded pairs (and no lone pairs)

* Electron pairs repel (one another equally)

Question 6

Explain what is meant by the term electronegativity and suggest why SF6 molecules are non-polar

Answer 6

• The ability of an atom to attract electrons
in a (covalent) bond
• The octahedral shape) is symmetrical

Question 7

What is the name of the term used to describe the repeating patterns in the Periodic Table

Answer 7

• Periodicity

Question 8

The melting points of three elements in Period 3
Melting point
Aluminium 660

Silicon 1410

Phosphorous 44

Answer 8

• Al has metallic (bonding)
• Si has covalent (bonding)
• P has induced dipoles (between molecules)
• Al AND Si are Giant
• P is Simple molecular OR simple covalent
• Metallic AND covalent are stronger than induced dipoles/More energy is needed to overcome bonds in Al AND Si than the forces in P

Question 9

Magnesium has a greater second ionisation energy than strontium. Explain why

Answer 9

• Mg(+) has smaller (ionic) radius OR has less shells
• (Outermost electron) of Mg(+) experience less shielding
• More nuclear attraction on (outermost electrons)

Question 10

Some scientist believe chlorine compounds should not be present in drinking water. Suggest why

Answer 10

• Chlorine compounds are carcinogenic

* Chlorine compounds are toxic or poisonous

Question 11

Aqueous chloride ions can be detected by adding aqueous silver nitrate. The appearance of solid silver cholride, AgCl, confirms the presence of chloride ions

Answer 11

• Precipitation

* Ag+(aq) + Cl–(aq)  AgCl(s)

Question 12

What is a dative covalent bond?

Answer 12

• Shared pair of electrons

* Both electrons are donated by one atom