Group 7: The Halogens Flashcards

All 7 cards in this deck

What are the Group 7 elements called, and how many outer electrons do their atoms have?

The halogens — seven outer electrons; they are non-metals made of molecules of pairs of atoms (e.g. $\mathrm{Cl_2}$).

What is the trend in melting and boiling points going down Group 7, and why?

They increase: relative molecular mass and molecule size increase, so intermolecular forces are stronger and more energy is needed to overcome them.

What is the trend in reactivity going down Group 7, and why?

Reactivity decreases: the outer shell is further from the nucleus, so there is less attraction for an incoming electron and an electron is gained less easily.

What type of compound is formed when chlorine, bromine or iodine reacts with a metal?

An ionic compound — a metal halide salt containing halide ions, e.g. sodium chloride.

True or false? Chlorine and hydrogen react to form an ionic compound.

False. Halogens react with non-metals to form covalent molecular compounds, e.g. hydrogen chloride, $\mathrm{HCl}$.

What are the steps to write the equation for a halogen displacement reaction?

e.g. chlorine added to potassium bromide solution

1. Check the added halogen is higher in Group 7 (more reactive): chlorine is above bromine, so a reaction happens
2. Swap the halogens: potassium chloride + bromine
3. Write and balance: $\mathrm{Cl_2} + 2\mathrm{KBr} \rightarrow 2\mathrm{KCl} + \mathrm{Br_2}$

True or false? Bromine will displace chlorine from potassium chloride solution.

False. Only a more reactive halogen displaces a less reactive one, and chlorine is more reactive than bromine.