Group 7 Flashcards

All 25 cards in this deck

What are the colour and physical state of chlorine at room temperature?

Pale green gas.

What are the colour and physical state of bromine at room temperature?

Red-brown liquid.

What are the colour and physical state of iodine at room temperature?

Dark grey solid.

What happens to melting point, boiling point and density going down Group 7?

They all increase down the group.

Using the trend in Group 7, predict the colour and physical state of astatine at room temperature.

Grey (or black) solid.

True or false? Fluorine is a solid at room temperature.

False. Fluorine is above chlorine in Group 7, so it is a gas (pale yellow).

What is the chemical test for chlorine gas?

Damp litmus paper is bleached (turns white).

What is seen when damp blue litmus paper is placed in chlorine gas?

It first turns red, then bleaches / turns white.

What type of compound is formed when a halogen reacts with a metal?

A metal halide (a salt).
e.g. iron + chlorine → iron chloride

What are the steps to write a balanced equation for a halogen reacting with a metal?
e.g. aluminium + bromine

1. Write the reactants, halogen as a diatomic molecule: $\mathrm{Al} + \mathrm{Br_2}$
2. Work out the metal halide formula from the charges: $\mathrm{AlBr_3}$
3. Balance: $2\mathrm{Al} + 3\mathrm{Br_2} \rightarrow 2\mathrm{AlBr_3}$

What do the halogens form when they react with hydrogen?

Hydrogen halides.
e.g. $\mathrm{H_2} + \mathrm{Cl_2} \rightarrow 2\mathrm{HCl}$

What is the name of the solution formed when hydrogen bromide dissolves in water?

Hydrobromic acid — hydrogen halides dissolve to form acidic solutions.

True or false? Fluorine reacts more vigorously with iron than iodine does.

True. Reactivity decreases down Group 7, so fluorine is the most vigorous.

What is a halogen displacement reaction?

A more reactive halogen takes the place of a less reactive halogen in a solution of its halide.

What is seen when chlorine water is added to colourless potassium bromide solution?

The colourless solution turns yellow / orange / brown, as bromine is displaced.

What are the steps to write the ionic equation for a halogen displacement reaction?
e.g. chlorine water added to sodium bromide solution

1. Write the halogen and the halide ions as reactants: $\mathrm{Cl_2} + 2\mathrm{Br^-}$
2. The halogen becomes halide ions and the halide ions become a halogen molecule: $\rightarrow 2\mathrm{Cl^-} + \mathrm{Br_2}$
3. Check the balancing: $\mathrm{Cl_2} + 2\mathrm{Br^-} \rightarrow 2\mathrm{Cl^-} + \mathrm{Br_2}$

What is the half equation for the formation of bromine from bromide ions?

$2\mathrm{Br^-} \rightarrow \mathrm{Br_2} + 2\mathrm{e^-}$

In a halogen displacement reaction, which species is oxidised and which is reduced?

The halide ions are oxidised (lose electrons); the halogen is reduced (gains electrons).

True or false? Iodine displaces chlorine from potassium chloride solution.

False. Iodine is less reactive than chlorine, so no reaction occurs.

What happens to reactivity going down Group 7?

It decreases — fluorine is the most reactive halogen.

How many electrons are in the outer shell of a Group 7 atom?

Seven.

In terms of electron shells, what makes it harder for a halogen atom lower down Group 7 to gain an electron?

Its outer shell is further from the nucleus and shielded by more inner shells, so the attraction for an extra electron is weaker.

What ion does a halogen atom form when it reacts?

A halide ion with a $1-$ charge, giving a full outer shell.
e.g. $\mathrm{Cl^-}$

True or false? Chlorine is more reactive than bromine because chlorine atoms lose electrons more easily.

False. Halogens gain electrons; a chlorine atom gains an electron more easily than a bromine atom.

Using the Group 7 trend, how reactive is astatine compared with the other halogens?

The least reactive — so iodine would displace astatine from a solution of an astatide.