Groups in the Periodic Table

Question 1

What are group 1 elements also known as?

Answer 1

Alkali metals

Question 2

Why do group 1 elements have similar chemical properties?

Answer 2

They have similar chemical properties as they all have one outer electron

Question 3

What are the physical properties of group 1 metals?

Answer 3

1. Low melting/boiling points

2. v soft (cut with a knife)

Question 4

What kind of compounds do the alkali metals form?

Answer 4

ionic compounds - they have one outer electron that can be lost so easily that they do not share in a covalent bond

Question 5

How reactive are the alkali metals?

Answer 5

• very reactive as they readily lose their single outer electron to form stable +1 ions
• become more reactive as you move down the group as the electron becomes more easily lost (since larger atomic radius and more shells to shelter electrostatic attraction)

Question 6

What is formed when an alkali metal reacts with cold water?

Answer 6

alkali metal + cold water -> (Metal) Hydroxide + Hydrogen Gas (H2)

Question 7

How do alkali metals react with cold water?

Answer 7

vigorously - increases down the group (as electron more easily lost):
lithium - moves around the surface fizzing
sodium - + melts
potassium - + ignites the H2 gas produced

Question 8

What are group 7 elements known as?

Answer 8

the halogens

Question 9

Why do group 7 elements have similar chemical properties?

Answer 9

they all have 7 outer electrons

Question 10

What bonds do halogens form?

Answer 10

exist in diatomic molecules (e.g. Cl2, Br2) sharing one pair of electrons in a covalent bonito give full outer shells

Question 11

What happens as you go down Group 7?

Answer 11

melting/boiling points increase, so at room temp:

1. Chlorine is a green gas (reactive/poisonous)
2. Bromine is a red-brown liquid that gives off an orange vapour (poisonous)
3. Iodine is a dark grey crystalline solid - gives off purple vapour when heated

Question 12

How can you test for chlorine?

Answer 12

using damp blue litmus paper - chlorine gas will bleach the paper white - may turn red at first as chlorine solution is slightly acidic

Question 13

How does reactivity change as you go down group 7?

Answer 13

decreases - only needs to gain one electron to form a 1- ion and the easier it is for this to happen, the more reactive it will be - so as you go down the group, it is harder to attract the extra electron as the outer shell is further from the nucleus

Question 14

What do the halogens react with?

Answer 14

1. Metals to form salts called metal halides
   e. g. Sodium + Chlorine -> Sodium Chloride
2. Hydrogen to form hydrogen halides
   e. g. Hydrogen + Chlorine -> Hydrogen Chloride
   - halogens higher up the group are more reactive (as they attract outer electrons more easily) but the way they react is similar

Question 15

How do halogens displace eachother?

Answer 15

1. a displacement reaction is where a more reactive element displaces a less reactive one from a compound
2. halogen displacement reactions are redox reactions (halogens a reduced and halide ions are oxidised)
3. e.g. chlorine is more reactive than bromine, so if you add chlorine water to potassium bromide, the chlorine will displace the bromine - chlorine is reduced (gain electrons) to chloride ions so the solution becomes potassium chloride - bromide ions are oxidised to bromine which turns the solution orange

Question 16

How can you use a displacement reaction to show reactivity trends of halogens?

Answer 16

1. measure out a small amount of a halide salt solution into a test tube
2. add drops of a halogen solution to it and shake the tube
3. if a colour change happens, that means a reaction has happened - the halide has displaced the halide ions from the salt - no colour change means the halogen is less reactive than the halide and can’t displace it
4. repeat this process with different combinations
5. you should find that chlorine displaces bromine (orange solution) and iodine (brown) from salt solutions, and that bromine displaces iodine (brown)

Question 17

What are group 0 elements called?

Answer 17

the noble gases

Question 18

What are the properties of the noble gases? (3)

Answer 18

1. colourless gases at room temp
2. monatomic - gases are made of single atoms
3. inert and non-flammable - don’t react much at all as have full outer electrons so difficult for them to gain or lose them
   - took a long time to be discovered as they are hard to be observed

Question 19

What are the noble gases used for? (3)

Answer 19

1. to provide inert atmospheres e.g. argon stops the filament in lamps from burning away and in flash photography to stop the flash filament burning up
2. argon and helium used to protect metals being welded - stops metal reacting with oxygen
3. helium used in airships and party balloons - lower density than air so makes balloons float and non-flammable so safer than hydrogen

Question 20

What are the patterns in the properties of the noble gases?

Answer 20

boiling/melting point and density increase as you go down