Topic 6 - Groups Of The Periodic Table

Question 1

What are group 1 metals known as?

Answer 1

Alkali metals

Question 2

Name the group 1 metals

Answer 2

Lithium 
Sodium 
Potassium 
Rubidium 
Caesium 
Francium

Question 3

How many electrons do alkali metals have in their outer shells

Answer 3

1

Question 4

What does the number of electrons on the outer shell of alkali metals mean?

Answer 4

They have very similar chemical properties

Question 5

State some physical properties of alkali metals

Answer 5

• Low melting points and boiling points compared with other metals
• very soft - they can be cut with a knife.

Question 6

Do alkali metals form ionic or covalent compounds and why?

Answer 6

Alkali metals form ionic compounds. They loose their single outer shell electron so easily that sharing it isn’t an option, this is why they don’t form covalent bonds.

Question 7

Are group 1 (alkali metals) reactive.

Answer 7

Yes, very

Question 8

Why are group 1 metals so reactive?

Answer 8

The group 1 metals readily loose their single outer electron to form a 1+ ion with a stable electronic structure.
The mor readily a metal looses its outer electrons the more reactive it is - so group 1 metals are very reactive

Question 9

What happens as you go down group 1

Answer 9

The Alkali metals get more reactive. The outer electron gets more easily lost as it is further from the nucleus ( the atomic radius is larger) so the attraction is weaker meaning less energy is required to remove it.

Question 10

What is produced when alkali metals react with water?

Answer 10

A hydroxide and a hydrogen

Question 11

How do alkali metals react when put in water

Answer 11

Vigorously

Question 12

Example: What is the equation for the reaction of sodium with water?

Answer 12

2Na + 2H2O -> 2NaOH + H2

Sodium + water -> sodium hydroxide + hydrogen

Question 13

The reactivity of group 1 metals with water (and dilute acid) increases down the group because the outer shell electron is lost more easily in the reaction, this results in the reaction becoming more violent.
Give some specific examples…

Answer 13

Lithium will move around the surface, effervescing furiously.

Sodium and potassium do the same, but they also me,t in the heat of the reaction. Potassium even gets hit enough to ignite the hydrogen gas that’s being released.

Question 14

What is group 7 of th periodic table known as?

Answer 14

Halogens

Question 15

Give some examples of halogens

Answer 15

Fluorine, chlorine, bromine, iodine and astatine

Question 16

How many electrons do halogens have on their outer shell? What does this say about their properties?

Answer 16

Halogens have 7 electrons on their outer shell, so they have very similar chemical properties

Question 17

What type of molecules are halogens, how does this effect their bonding?

Answer 17

Halogens exist as diatomic particles so sharing one pair of atoms in covalent bonds gives both atoms a full outer shell

Question 18

What happens as you go down group 7?

Answer 18

The melting points and boiling points increase

Question 19

What is chlorine like at room temperature? (Considering the fact that the melting and boiling points of halogens increase as you go down the table)

Answer 19

A fairly reactive, poisonous green gas.

Question 20

What is bromine like at room temperature? (Considering the fact that the melting and boiling points of halogens increase as you go down the table)

Answer 20

A poisonous, red-brown liquid, which gives off orange vapour at room temp.

Question 21

What is iodine like at room temperature? (Considering the fact that the melting and boiling points of halogens increase as you go down the table)

Answer 21

A dark grey crystalline solid which gives off a purple vapour when heated.

Question 22

Describe the test for chlorine

Answer 22

You can see if a gas is chlorine by holding a piece of damp blue litmus paper over it. Chlorine will bleach the litmus paper, turning it white. It may also turn red for a moment first - that’s because chlorine is acidic.

Question 23

Does reactivity decrease or increase going down group 7? And why?

Answer 23

Decrease this is because a halogen atom only needs to gain one atom to form a 1- ion with a stable electronic structure .
The easier it is for a halogen to attract an atom the more reactive it will be.
As you go down group 7 the halogens get less reactive - it gets harder to attract the extra electron to fill the outer shell as it’s further away from the nucleus (the atomic radius). The attraction from the positive nucleus to the negative electrons is weaker.

Question 24

What do the halogens commonly react with?

Answer 24

Metals and hydrogen.

Question 25

How do halogens react with metals and what are the products?

Answer 25

Halogens react vigorously with some metals to form salts and ‘metal halides’

Question 26

Explain the reaction of halides with hydrogen and the properties of the products formed.

Answer 26

Halogens can react with hydrogen to form hydrogen halides. Hydrogen halides are soluble and so can dissolve in water to form acidic solutions for example HCL forms hydrochloride acid in water.

Question 27

What does the fact that all halogens have the same amount of electrons in their outer shell say about them?

Answer 27

Since all halogens have 1 electron on their outer shell, they all have similar reactions. So you can use the reactions of chlorine, bromine and iodine to predict how fluorine and astatine will react.

Question 28

True or false: A more reactive halogen will displace a less reactive one.

Answer 28

True

Question 29

Explain displacement reactions

Answer 29

Displacement reactions are where a more reactive element ‘pushes out’ (displaces) a less reactive element from a compound.

Question 30

What type of reactions are halogen displacement reactions? Explain

Answer 30

They are REDOX reactions. That halogens gain electrons (reduction) whilst the halide ions loose electrons (oxidation).

Question 31

Explain: chlorine + potassium bromide -> bromine + potassium chloride

Answer 31

Chlorine is more reactive then bromine (its higher up group 7). If you add chlorine water (an aqueous solution of Cl) to potassium bromide solution the chlorine will replace the bromine from the salt solution. The chlorine is reduced to chloride ions, and so the salt solution becomes potassium chloride. The bromide atoms are oxidised to bromine, which turns the solution orangey.