Chapter 7- Periodicity Flashcards
Define ionisation energy.
The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions.
Na(g) → Na^+(g) + e^-
What three factors affect ionisation energy?
- Atomic radius- the greater the radius the less attraction
- Nuclear charge- the more protons the increased attraction between the nucleus and the outer e^-.
- Electron shielding- shielding reduces the attraction between the nucleus and the outer e^-.
What is the trend in first ionisation down group eight?
- The atomic radius increases.
- There are more inner shells so shielding increases.
- Nuclear attraction on outer electrons decreases.
- First ionisation energy decreases.
What is the trend in first ionisation as you go along a period and why?
- The nuclear charge increases.
- They have the same shell so similar shielding.
- The nuclear attraction increases.
- The atomic radius decreases.
- First ionisation energy increases.
Why may there be rises and falls in the first ionisation energy as you go along the second period?
- There’s a fall from nitrogen to oxygen due to oxygen having one more e^- in the 2p subshell, resulting in a pair of e^- in one of the orbitals that repel making it easier to remove.
- There’s a fall from Be to B as the additional e^- in B compared to Be is found in the 2p shell so has a higher energy level and so is easier to remove.
Describe metallic bonding.
The strong electrostatic attraction between cations and delocalised electrons. The cations are in a fixed position maintaining the structure and shape of the metal. The delocalise e^- are mobile so can move throughout the whole structure.
Describe the properties of metals.
- strong metallic bonds.
- high electrical conductivity.
- high melting and boiling points.
In metallic bonding if each cation has a charge of 2+ how many delocalised e^- are there per atom?
2 delocalised e^-.
Describe the solubility of giant covalent lattices.
They’re insoluble in almost all solvents. The covalent bonds holding together the atoms in the lattice are far too strong to be broken by interactions with solvents.
Describe the billing point of covalent lattices.
They have a high boiling point, due to strong covalent bonds that require more energy to be broken.
Can diamond conduct electricity?
No as all four outer shell e^- are involved in covalent bonding, so they’re not mobile to conduct electricity.
Which carbon based structure is known for conducting electricity?
Graphene/ graphite
Describe the structure of graphite.
Parallel layers of hexagonally arranged carbon atoms. The layers are bonded weakly by London forces.
Why does Si have a greater melting point than P?
Si is a giant covalent structure.
How did Mendeleev organise the periodic table?
In order of atomic mass, swapping elements and leaving gaps for others that he predicted would be discovered.
