Groups in the Periodic Table (PAPER TWO) Flashcards
What happens when Lithium, sodium and potassium are put in water?
Lithium - move around the surface, fizzing furiously
Sodium and potassium - do the same but melt in the reaction’s heat. Potassium ignites the hydrogen gas being produced
What’s the word equation for sodium and water?
Sodium + water –> Sodium hydroxide + hydrogen
What are group 1 metals known as?
Alkali Metals
What are some characteristics of the Alkali metals?
Properties similar to other metals:
- Malleable
- Conduct electricity
Properties specific to group 1:
Very reactive
Easily cut
Very soft
Low melting point
Readily form compounds with other metals
How do you calculate relative atomic mass?
(mass number a x isotope abundance a) + (mass number b x isotope abundance b)
divided by
Isotope abundance a + b
What’s an isotope?
Atoms of the same element with the same number of protons and a different number of neutrons
What are the products when alkali metals are put in water?
Hydrogen and a metal hydroxide
At which point in group 1 is reactivity the highest?
Reactivity increases as you go down the group
Explain the trend of reactivity in group 1
- Reactivity increases as you move down the group
- This is because, an extra electron shell is added each period (the atom gets bigger)
- So, the force of attraction between the negatively charged outer electron and positively charged nucleus decreases as they get further apart (electrons are more easily lost the further away they are from the nucleus due to the weaker force of attraction, hence them being more reactive)
What are elements in group 7 known as?
Halogens
How are the halogens similar?
- diatomic molecules with 2 atoms held together by a single covalent bond
- All non-metallic (poor conductors of heat and electricity)
- Toxic and corrosive
How do chlorine, bromine and iodine look?
Chlorine - green gas
Bromine - brown liquid
Iodine - purple/black solid
What happens when halogens react with metals?
They form ionic compounds called salts that contain halide ions
Chlorine + magnesium —->
Magnesium chloride
Name some uses for halide salts
Sodium chloride - table salt
Sodium fluoride - Toothpaste
Sodium bromide - disinfectant for swimming pools
Sodium iodide - added to table salt to prevent iodine deficiency
What can all halogens be used for and why?
Disinfectants and bleaches: they can kill microorganisms and remove colour from material
How can you test for chlorine gas?
Place damp blue litmus paper in the gas. If it turns red, then bleaches white, the gas is chlorine.
How can the reactivity of halogens be determined using displacement reactions?
A more reactive halogen will displace a less reactive halogen from a halide compound
Chlorine + sodium bromide —>
Bromine + Sodium chloride
(chlorine is more reactive than bromine, so it displaces it)
Explain the order of reactivity of halogens in relation to the electronic configuration
- Reactivity of halogens decrease as you go down the group
- Halogens gain 1 electron to get a full outer shell and become stable
- So, halogens at the top of the group have their outer shells closer to the nucleus meaning the force of attraction between the incoming electron and nucleus is stronger
Why are displacement reactions redox reactions?
Both reduction and oxidation occurs in displacement reactions, making them examples of redox reactions
What are the elements in group 0 known as?
Noble Gases
What are the properties of the noble gases?
- Colourless
- Very low melting and boiling points
- Poor conductors of heat and electricity
Explain why noble gases are chemically inert
Atoms gain, lose or share electrons to get a full outer shell and become more stable. Noble gases already have a stable electronic configuration with a full outer shell, so they are unreactive.
Explain some uses/examples of Noble Gases
Helium: very low density, non flammable - used in weather balloons and airships
Argon: Denser than air - added to the space above wine in wine bottles to stop the oxygen in the air from reacting with the wine
Krypton: produces a white light when electricity is passed through it - used in photography lighting
Neon: produces a distinctive red-orange light when electricity is passed through it - used in the making of long-lasting illuminated signs
Why was the noble gas group not known until the end of the 19th century?
Elements were difficult to detect as they don’t react with anything
Describe the trends in the physical properties
of the noble gases
Melting point, density and boiling point increases as you go down the group
Explain why chlorine is a gas, rather than a liquid, at room temperature
- Intermolecular forces between molecules are weak
- So, the boiling point is below room temperature
