2.3.2 Chemical Properties of Group 7 Flashcards
How are halogens oxidising agents?
- Oxidise metals by removing an electron from them
- Halogen becomes reduced, gaining an electron
Ca (s) + Cl2 (g) → CaCl2 (s) consisting of Ca2+ and 2Cl- ions
How does oxidising power change down group 7?
Decreases down group, halogen becomes less reactive, outer shell further from nucleus, so weaker attraction from nucleus to electrons of other atoms, and more shielding, so less tendency to act as an oxidising agent
What is electronegativity?
Ho strongly an atom attracts electrons towards itself in a covalent bond
How does it change down group 7?
- Electronegativity decreases down group
- Atomic radii increases
- Outer shell further away from nucleus
- Incoming electrons have more shielding and less attraction to nucleus
- So ability to accept electrons (oxidising power) decreases
What is one way you can demonstrate reactivity changes in halogens going down the group?
- Ability to displace other halides
- More reactive halogen displaces a less reactive halogen from a halide solution of the less reactive halide
Cl2 (aq) + 2NaBr (aq) → 2NaCl (aq) + Br2 (aq)
Ionic equation :
Cl2 (aq) + 2Br- (aq) → 2Cl- (aq) + Br2 (aq)
How do reactions with hydrogen change going down group?
What is thermal stability?
How well a substance can resist breaking down when heated, a substance with a high thermal stability only breaks down at high temperatures
How does thermal stability in Hydrogen halide complexes change down group?
- Decrease going down group
- Bond energies
- Atomic radii increases down group
- So overlapping outer shell with H atom is more difficult
- Weaker bond, less energy required to break it
How can halide ions act as reducing agents?
- ions can donate electrons
- And get oxidised themselves and lose electrons
- Reducing power increases going down group
- Ionic radii increases
- Less attraction to nucleus
- More shielding
- Easily lost
