Common questions involving explanations
1) State and explain the trend of electro negativity values across period 3.
 Increases
(a) Nuclear charge increases
(b) Electrons in the same shell
(c) Similar shielding
2) What is meant by the term first ionisation energy
 The amount of energy required for the removal of one mole of electrons
from one mole of gaseous atoms.
3) Why has magnesium got a higher melting point than sodium
 Magnesium has :
(a) More protons/greater nuclear charge
(b) More delocalised electrons
(c) Smaller atomic radius therefore stronger attraction between ‘ions’ and
delocalised electrons as the electrons are closer to the nuclei.
4) Why do diamond and graphite both have high melting points
 They have macromolecular structures
 Covalent bonds as intramolecular bonds
 Strong bonds therefore require a large amount of energy to break them.
5) Define the term electron density
 [The power of an atom to withdraw some electron density from a covalent bond]
Or
[power of an atom to attract a pair of electrons in a covalent bond]
6) In terms of intermolecular forces suggest why HF has a higher melting point than HCl
 Hydrogen bonding in HF
 Dipole-Dipole in HCl
 Hydrogen bonding is stronger
7) In terms of Intermolecular forces suggest why HI has a higher melting point than HCl
 HI has a larger Mr/ Is a larger molecule
 Van Der Waals forces are stronger
8) Explain why Sodium chloride has a high melting point
 Strong electrostatic forces of attraction between Na+ and Cl-
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

Forms Ionic lattice
High energy required to break the strong bonds
9) State with a reason the trend in atomic radius going down group 2
 Increases
(1) Increased number of energy levels
10) State with a reason the trend in electro negativity down group 2
 Decreases
(1) Atoms increase in size
(2) More shielding
(3) Weaker attraction between nucleus and bonding pair
11) State with a reason the trend in reactivity down Group 2
 Increases
(1) Outer electrons further away from nucleus
(2) Increase in shielding therefore weaker attraction between nucleus and
outermost electron.
12) State and explain the general trend of first I.E values across period three
 Increases
(1) Increase in nuclear charge
(2) Similar shielding
(3) Stronger attraction of outer electron and positively charged nucleus
13) State and explain how the value for Aluminium deviates from that trend
 Lower than Magnesium
(1) Electron is removed from 3p orbital
(2) Higher in energy than 3s (as in magnesium’s electron is removed from 3s)
(3) More shielded than 3s
14) State and explain how the value for sulphur deviates from the trend
 Lower
(1) Electron is removed from 3p electron pair
(2) There is repulsion between pair which reduces energy required to remove
the electron
15) State the difference between the chemical properties of the isotopes of an element
 There is no difference. Isotopes of an element all have the same number of
electrons. The electron configuration is what determines the chemical
properties.
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16) Explain why metals can conduct electricity
 They have delocalised electrons which move in a given direction
17) In terms of structure and bonding explain why sulphur has a higher melting point than
phosphorous
 Both have VdW as intermolecular forces
 S is a larger molecule
 S8 compared to P4
 Therefore S8 has stronger VdW
18) Why does diamond have a much higher melting point than iodine
 Diamond is a Giant covalent structure
 Iodine has covalent bond but only within molecules
 VdW is ther intermolecular force within Iodine which are easily overcome
19) Explain why the first I.E of Neon is higher than that of Sodium
 Mg has a bigger nuclear charge
 Mg is a smaller atom
 Similar shielding
20) Neon and Mg2+ (magnesium II ion) both have the same electron structure give TWO
reasons why the third ionisation energy of Mg is higher than the first I.E of neon
 Mg Ion has more protons than Ne
 Mg ion has smaller atomic radius than Ne
21) Explain the trend in the boiling points from HCL to HI
 HI has larger Mr/ is a larger molecule
 VdW forces are stronger
22) Compare and explain the electrical conductivity of sodium metal and sodium chloride
 NaCl does not conduct, Na does
 Ions in Solid NaCl cannot move (must be in molten/aqueous state)
 Na has delocalised electrons flowing through the metal.
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