Alkali Metals and Halogens Flashcards
(24 cards)
What are Group 1 elements known as?
The alkali metals.
What do Group 1 metals all have in common regarding water reactions?
They react vigorously with water to form an alkali (metal hydroxide) and hydrogen gas.
What is the word equation for sodium reacting with water?
Sodium + water → sodium hydroxide + hydrogen
What is the balanced symbol equation for sodium reacting with water?
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
What happens when Group 1 metals react with oxygen?
They form metal oxides and tarnish in air.
What oxide does lithium form?
Lithium oxide (Li₂O)
What oxides does sodium form?
Sodium oxide (Na₂O) and sodium peroxide (Na₂O₂)
What oxides does potassium form?
Potassium peroxide (K₂O₂) and potassium superoxide (KO₂)
What trend in reactivity is seen down Group 1?
Reactivity increases down the group.
Why does reactivity increase down Group 1?
- Atoms get bigger
- Outer electron is further from nucleus
- Weaker attraction to the nucleus
- Easier to lose the outer electron
What are Group 7 elements called?
The halogens
What happens to colour and boiling point down Group 7?
- Colour gets darker
- Boiling point gets higher
What happens to reactivity down Group 7?
Reactivity decreases.
Why does reactivity decrease down Group 7?
- Larger atomic radius
- Outer shell further from nucleus
- Harder to gain an electron
What is a displacement reaction?
When a more reactive halogen displaces a less reactive one from a compound.
What happens when chlorine water is added to potassium iodide solution?
Chlorine displaces iodine. Solution turns brown.
Equation: Cl₂ + 2KI → 2KCl + I₂
In the above reaction, which is oxidised and which is reduced?
- Chlorine is reduced (gains electrons)
- Iodine is oxidised (loses electrons)
What is the meaning of OIL RIG?
Oxidation Is Loss, Reduction Is Gain (of electrons)
What is a redox reaction?
A reaction where both oxidation and reduction occur simultaneously.
In a redox reaction, what is the oxidising agent?
The substance that gains electrons (gets reduced).
What is the reducing agent?
The substance that loses electrons (gets oxidised).
Chlorine
- Fairly reactive, poisonous green gas
Bromine
- Poisonous, red-brown liquid
- Gives off an orange vapour at room temp
Iodine
- Dark grey crystalline solid
- Gives off a purple vapour when heated
