January 17, 2022
Periodicity
In I/GCSE Chemistry, Regular periodic variation of properties of element with atomic number and position in Periodic Table.
Trends down group 7 chemical properties
1) 1st IONISATION ENERGY & ATOMIC RADIUS: DECREASES
- Number of shells increases- so distance of outer electrons from nucleus increases, increasing atomic radius- weaker force of attraction on outer electrons
- More inner shells- shielding effect on outer electrons from nuclear charge increases- less attraction
2)MELTING + BOILING POINT: INCREASES
- Molecules get larger-
- Stronger the intermolecular forces, higher amount of energy is needed to break down molecules- higher melting + boiling point
Group 7 elements: Uses & Halide Test
In I/GCSE Chemistry, group 7 elements
- Become less reactive down the group
- React with metals to form ionic halides with an X⁻ ion
- Bonding: Covalent diatomic molecules
- Structure: Simple molecular- weak VDW forces between diatomic molecules
TEST FOR HALIDES
- Unknown halide substance is dissolved in water
- Aqueous solution of silver nitrate, AgNO₃(aq) is added
- Forming a silver halide precipitate
- All halides are INSOLUBLE except Fluorine- which is SOLUBLE in water
If you’re unsure to judge the colour:
- Aqueous ammonia, NH₃(aq) can be added
You got it now!