3 - Physical Properties of Group 7 & Strength as Oxidising Agents

What is the appearance of Group 7?

F - pale yellow gas

Cl - pale green gas

Br - red-brown liquid

I - black solid

At - no photos

What are Group 7 as elements?

Diatomic

F₂, Cl₂, Br₂, I₂, At₂

How does atomic radii change down Group 7?

Increases

Why does atomic radii change down Group 7?

Extra energy level of electrons down the group

How does electronegativity change down Group 7?

Decreases

Why does electronegativity change down Group 7?

Outer energy level of electrons is further from the nucleus

Bonding pair of electrons less strongly attracted to the nucleus

How do melting/boiling points change down Group 7?

Increases

Why do melting/boiling points change down Group 7?

More electrons down the group

Stronger van der Waals forces

More energy required to overcome

If a halogen (X₂) is added to a halogen solution (HY) and there is **no** **colour change**, which halogen is the strongest oxidising agent?

X₂(aq) + HY(aq) → no reaction

X₂ is not as strong an oxidising agent as Y⁻

If a halogen (Y₂) is added to a halogen solution (HX) and there is **a** **colour change**, which halogen is the strongest oxidising agent?

Y₂(aq) + HX(aq) → reaction

Y₂ is a stronger oxidising agent than X⁻

How does strength as a oxidising agent change down Group 7 as molecules (X₂)?

Decreases

How does strength as a reducing agent change down Group 7 as ions (X⁻)?

Increases

What is the equation and half equation for the reaction of chlorine with potassium bromide and which species is oxidised/reduced?

Cl₂(aq) + 2KBr(aq) → 2KCl(aq) + Br₂(aq)

Cl₂(aq) + 2Br⁻(aq) → 2Cl⁻(aq) + Br₂(aq)

Cl₂ - gains 2 electrons, is reduced, oxidises 2Br⁻

2Br⁻ - loses 2 electrons, is oxidised, reduces Cl₂