Periodicity Flashcards
(12 cards)
What is periodicity?
The repeating pattern of properties of elements across different periods in the periodic table
What is the structure of the periodic table?
- 8 main groups
- 4 periods of transition metals between main group 2 and 3
- elements are arranged in order of atomic number
- encloses elements in boxes and displays them in groups (vertical) and periods (horizontal)
What is first ionisation energy?
The energy required to remove one mole of electrons from one mole of gaseous atoms
X(g) ———> X+(g) + e-
Endothermic
What factors influence ionisation energy?
- nuclear charge (number of protons) = more protons means greater nuclear charge
- atomic radius = nuclear attraction is reduced by increased distance = further the electrons from the nucleus, the less energy required to remove
- shielding effect = inner shell electrons repel the outer electrons, reducing the attraction experienced by the outer electrons from the nucleus
What is the trend in ionisation energy across a period (L—>R)?
- nuclear charge increases
- atomic radius increases
- shielding remains the same
- nuclear attraction increases
- outer electron requires more energy to remove
- ionisation energy increases across a period
What is the trend in ionisation energy down a group?
- nuclear charge increases
- atomic radius increases
- shielding increases
- nuclear attraction decreases
- outer electron requires less energy to remove
- ionisation energy decreases down a group
Why are there drops in ionisation energy between Be and B and N and O?
Be vs B = group 2 vs 3
N vs O = group 5 vs 6
Why are successive ionisation energies good?
- electronic configurations can be predicted from successive ionisation energy data
- successive ionisation energies provide evidence for different energy levels
Why might the 3rd ionisation energy be greater than the second ionisation energy?
The third electron is removed from the lower main energy level/shell
What are the periodic trends in metallic bonding?
Fixed metal cations are surrounded by mobile, delocalised electrons meaning metals can conduct both as solids and liquids
Strong metallic bonds mean high temperatures are needed to provide the large amount of energy needed to overcome the electrostatic attraction between the cations and electrons, so there are high melting and boiling points
What are the periodic trends in giant covalent structures?
Network of strong covalent bonds require more energy to overcome so there are high melting and boiling points
Insoluble in most solvents as the bonds are too strong to be broken by interactions with solvent molecules
Most don’t conduct electricity as all the outer shell electrons are involved in covalent bonding, except graphite and graphene as they have mobile, delocalised electrons
Why does ionisation energy increase each time an electron is removed?
Proton:electron ratio increases
One less electron each time
