2014 Atoms, Bonds and Groups

Question 1

What is meant by the term isotopes

Answer 1

• Atom(s) of an element

* With different numbers of neutrons (and with different masses)

Question 2

Different isotopes of an element have the same chemical properties. Explain why

Answer 2

• Same number of electrons in outer shell

Question 3

Define the term relative atomic mass

Answer 3

• The weighted mean mass of an atom of an element
• Compared with 1/12th the mass
• Of one atom of carbon-12

Question 4

Predict the shape of a molecule of SbCl3

Answer 4

• Trigonal Pyramidal
• Sb has three bonding pairs AND one lone pair of electrons
• Pairs of electrons repel

Question 5

SbCl3 molecules are polar

Explain why

Answer 5

• There is a difference in electronegativities (between Sb and Cl)
• Sb-Cl bonds are polar OR have a dipole OR dipoles seen on the diagram
• The molecule is not symmetrical
• Dipoles do not cancel

Question 6

State and explain two anomalous properties of ice caused by hydrogen bonding

Answer 6

• Ice is less dense than water
-The molecules in ice are held apart by hydrogen bonds OR ice has an open lattice/structure
• Ice has a relatively high melting point
-Hydrogen bonds are relatively strong

Question 7

Describe and explain the electrical conductivity of sodium oxide, Na2O, and sodium in their solid and molten states

Answer 7

• Sodium conducts in the solid and molten states
• Sodium has delocalised electrons(in both solid and liquid state)
Na2O conducts when molten and not when solid
• Molten Na2O has ions which are mobile
• Solid Na2O has ions which are fixed(in position)/ions are held (in position)/ions are not mobile
• In an ionic lattice/structure

Question 8

Silicon dioxide, SiO2, has the same structure and bonding as diamond

State the structure and bonding in SiO2

Answer 8

• Giant covalent lattice

Question 9

State and explain the trend in atomic radius from Li to F

Answer 9

Trend
• Atomic radius decreases
• Nuclear charge increases
• Outer electrons are in same shell/same number of shells
• Greater nuclear attraction on (outer) electrons or shells

Question 10

A student adds a small volume of aqueous silver nitrate to an aqueous solution of bromide ions in a test-tube. The student then adds a similar volume of dilute aqueous ammonia to the same test-tube

Describe what the student would see in the test-tube after the addition of aqueous ammonia

Answer 10

• Cream and precipitate
Ionic Equation
Ag+(aq) + Br–(aq) -> AgBr(s)

Question 11

Chlorine reacts with aqueous sodium hydroxideto form bleach

Answer 11

• 2NaOH + Cl2 -> NaCl + NaClO + H2O

Conditions
• Cold and dilute(sodium hydroxide)

Question 12

What is meant by disproportionation

Answer 12

• Is the simultaneous oxidation and reduction of the same element in the same redox reaction