Topic 4 - Group 1 & 7

Question 1

Describe the formation of ions by the loss and gain of electrons

Answer 1

• Electrons are transferred from one atom to another (this is in an effort to either fill or empty the outer shell to become stable.)
• An atom has no charge because the electrons and protons have equal and opposite charges.
• But an ion will have a charge: an electron has a charge of -1, so loosing an electron looses one negative charge, making the ion +1. So gaining one electron will make an atom a -1, gaining two will make it -2.

Question 2

Describe the relative reactivities of the elements in Group 7

Answer 2

• Group 7 elements become less reactive as you go down the group.
• At the top, the positive charge of the proton in the nucleus is close to the surface (as there are few shells) this makes it easy for them to pull in the one electron they need to become stable, meaning they are very reactive.
• Lower down where there are more shells the pull of the proton is further from the surface making it less easy to pull in another electron.

Question 3

Describe experiments to demonstrate that a more reactive halogen will displace a less reactive halogen from a solution of one of its salts

Answer 3

A more reactive halogen will displace a less reactive one that is bonded as a salt. This will only happen if the salt is dissolved in water or a gas.