Periodicity Flashcards
Define periodicity.
Repeating trends of physical and chemical properties across the periodic table.
How to answer a question which asks why an element is in a particular block of the periodic table?
“It’s highest occupied sub-shell is an s/p/d/f sub-shell.”
Describe the trend in ionisation energies going down a group.
SNAI:
1. Shielding increases going down the group
2. Nuclear attraction on outer e- decreases
3. Atomic radius increases
4. 1st ionisation energy decreases.
Define 1st ionisation energy.
The energy required to remove 1 mol of e-, from 1 mol of gaseous atoms, to form 1 mol of gaseous + ions.
Describe the general trend in 1st ionisation energies going across a period.
SNAI
1. Shielding stays the same across period
2. Nuclear attraction on outer e- increases
3. Atomic radius decreases
4. 1st IE generally increases.
Explain the 2 anomalies in 1st IE across periods 2, 3, 4.
Group 3:
- outer e- is in a higher energy p subshell
- nuclear attraction on outer e- decreases
- outer e- easier to take so 1st IE decreases.
Group 6:
- there is a pair of e- in a p orbital
- the pair of e- repels
- so due to extra repulsion, less energy needed to take outer e-
- 1st IE decreases.
Explain the trend in successive IEs.
Successive IEs always increase as:
PISN
- positive charge on ion increases (as e- are taken off)
- ionic radius decreases
- shielding stays the same
- nuclear attraction on outer e- increases
- IE increases.
Every now and then there is a big jump in IE as e- is taken from a shell closer to nucleus.
What structure do Group 4 elements form?
Giant Covalent
What type of bonding is present in Group 4 elements?
Covalent
What is the bonding arrangement of each atom in DIAMOND?
Each atom bonded to 4 others (tetrahedral)
How are carbon atoms arranged in GRAPHITE?
Each C atom bonded to 3 others (tri-planar)
What type of forces exist between layers in GRAPHITE?
Weak London Forces.
What characteristic of GRAPHITE allows it to conduct electricity?
Delocalised electrons
What is GRAPHENE?
1 layer of GRAPHITE
What is a common property of ALL Group 4 giant covalent structures?
High melting point and boiling point
Why is DIAMOND considered hard?
Each atom bonded to 4 others, strong cov. bonds require lots of energy to break.
Why is GRAPHITE considered soft?
Layers slide over each other
Metals are malleable and ductile. What does this mean? Why?
They can be hammered into shape and stretched into wires, due to their layers of ions which can slide over each other.
How to compare boiling points of giant metallic structures?
Greater positive ionic charge -> more delocalised e- -> ionic radius decreases -> SEABPMIADE strength increases -> more energy required to break.
