Model Answers Flashcards
State the meaning of the term electronegativity
The ability of the nucleus to attract a pair of electrons in a covalent bond
Describe the trends in electronegativity in the periods and groups of the periodic table
It increases along the periods and decreases slightly down the groups
State the three factors that affect the electronegativity of an element
Molecular size
Atomic radius
Electron shielding
Nitrogen (IV) oxide is a gas which dissolves in water in the atmosphere to form acid rain.
Electronegativity of nitrogen 3.006
Electronegativity of oxygen 3.610
Explain the two types of intermolecular force that exists in nitrogen (IV) oxide.
- Nitrogen (IV) oxide is polar as oxygen is more electronegative than nitrogen so it has permanent dipole - dipole forces.
- It also has induced dipole - dipole forces.
Silicon has four electrons in the third energy level.
Explain the arrangement of the electrons in the third energy level of silicon.
Si is 1s2 2s2 2p6 3s2 3p2. The third energy level has 2 electrons in an s orbital and 2 electrons in a p orbital. The s level fills first as it is a lower energy level.
Explain why the first ionisation energy of silicon (789 kJ mol-1) is greater than that of germanium (762 kJ mol-1).
Germanium has an extra shell of electrons on it, so the force between the nucleus and outer electrons is less than that of silicon.
The production of the ionic compound calcium chloride is an important industrial process.
Calcium chloride has a large range of uses, for example in the pharmaceutical industry and in the food industry.
State the name of the force between the calcium and chloride ions.
Electrostatic force
Write the balanced equation for the reaction of aluminium in air to form aluminium oxide
4Al + 3O2 –> 2Al2O3
Most metals have high melting and boiling points.
The table shows the melting and boiling points of three metals: sodium, magnesium and potassium
Discuss the different melting and boiling points of the three metals and the trends they show.
Sodium and magnesium are both in period 3, but the melting and boiling points of magnesium are greater than those of sodium because magnesium has 2 electrons in it’s outer shell and sodium only has 1. This means there is stronger attraction between the positive nuclei and delocalised electrons in magnesium so more energy is needed to break the metallic bonds. Potassium has lower melting and boiling points than sodiu, because it is lower down in group 1 so it has more electron shells. This means there is more shielding so less attraction between the nuclei and the delocalised electrons making the metallic bond weaker so less energy is needed to break it.
