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This question is about oxygen and substances containing oxygen - AQA - GCSE Chemistry - Question 3 - 2017 - Paper 1
Question 3
This question is about oxygen and substances containing oxygen. 3 (a) (i) Complete Figure 4 to show the arrangement of the outer shell electrons in an oxygen molecu... show full transcript
Worked Solution & Example Answer:This question is about oxygen and substances containing oxygen - AQA - GCSE Chemistry - Question 3 - 2017 - Paper 1
Step 1
Complete Figure 4 to show the arrangement of the outer shell electrons in an oxygen molecule.
Answer
In Figure 4, the outer shell of the oxygen molecule (O₂) consists of 6 electrons from each oxygen atom, making a total of 12 electrons. To represent this:
- Place 4 crosses (×) in one circle (representing one oxygen atom).
- Place 4 dots (•) in the other circle (representing the other oxygen atom).
- Additionally, show shared pairs of electrons by placing 2 crosses and 2 dots in the overlapping section of the two circles.
Step 2
Step 3
Explain why oxygen has a low boiling point.
Answer
Oxygen has a low boiling point due to the presence of weak intermolecular forces known as van der Waals forces. The O₂ molecules are small and relatively non-polar, leading to minimal attractive forces between them. As a result, less energy is needed to overcome these forces, allowing it to boil at low temperatures.
Step 4
Step 5
Describe what happens, in terms of electrons, when magnesium atoms react with oxygen atoms to produce magnesium oxide.
Answer
When magnesium reacts with oxygen, the magnesium atoms lose electrons while oxygen atoms gain electrons. Magnesium, which has two electrons in its outer shell, loses these two electrons to achieve a stable electronic configuration similar to a noble gas. The oxygen atoms gain these electrons to fill their outer shell. This transfer of electrons results in the formation of Mg²⁺ ions and O²⁻ ions, leading to the formation of magnesium oxide (MgO) through ionic bonding.
Step 6
Step 7
Explain, in terms of structure and bonding, why silicon dioxide is used to line furnaces.
Answer
Silicon dioxide has a high melting point because it forms a giant covalent structure in which many silicon atoms are bonded to oxygen atoms. Each silicon atom is bonded to four oxygen atoms, creating a strong, stable lattice. Breaking these strong covalent bonds requires a significant amount of energy, which is why silicon dioxide does not easily melt and is suitable for lining furnaces that operate at high temperatures.