Group 1 (alkali metals) (Edexcel IGCSE Chemistry (Modular): Unit 2): Flashcards
Exam code: 4XCH1
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What are alkali metals?
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What are alkali metals?
The alkali metals are the Group 1 elements: lithium, sodium, potassium, rubidium, caesium and francium. They are soft, reactive metals that each have one electron in their outer shell and form alkaline solutions when they react with water.
Why are Group 1 metals called alkali metals?
Group 1 metals are called alkali metals because they form alkaline solutions (pH above 7) when they react with water. For example, sodium reacts with water to produce sodium hydroxide solution.
The general equation for an alkali metal reacting with water is: alkali metal + water → .......... + .......... .
The general equation for an alkali metal reacting with water is: alkali metal + water → metal hydroxide + hydrogen.
True or False?
Potassium reacts more vigorously with water than lithium.
True.
Potassium is further down Group 1 than lithium, so the outer electron is further from the nucleus and held less strongly, making potassium more reactive and its reaction with water more vigorous.
What are the observations when potassium reacts with water?
When potassium reacts with water, it moves very rapidly across the surface, dissolves quickly, produces vigorous fizzing as hydrogen gas is released, and burns with a lilac flame.
Complete the observations for each alkali metal reacting with water.
Element
Observations
Li
Na
K
Complete the observations for each alkali metal reacting with water.
Element
Observations
Li
Relatively slow reaction; fizzing; moves on the surface of the water
Na
More vigorous fizzing; moves rapidly on the surface; dissolves quickly
K
Burns with a lilac flame; moves very rapidly on the surface; dissolves very quickly
What is tarnishing in alkali metals?
Tarnishing is when alkali metals react with oxygen in the air to form a dull metal oxide coating on the surface. Alkali metals tarnish more rapidly the further down the group you go.
How do melting points change as you go down Group 1, and why?
Melting points decrease as you go down Group 1. This happens because the attractive forces between the outer electrons and the positive metal ions become weaker as atoms get larger, so less energy is needed to melt the metal.
True or False?
Francium is the least reactive alkali metal.
False.
Francium is at the bottom of Group 1, making it the most reactive alkali metal. Lithium, at the top of the group, is the least reactive.
What is the electronic configuration of Group 1 elements?
Electronic configuration of Group 1 elements refers to the arrangement of electrons in their shells. All Group 1 atoms have one electron in their outermost shell, which they lose when reacting to form 1+ ions with noble gas configuration.
True or False?
The reactivity of Group 1 metals increases as you go down the group.
True.
As you go down Group 1, the outer electron is in a shell further from the nucleus, so the attractive force between the nucleus and the outer electron is weaker. Less energy is needed to remove it, making the metal more reactive.
Why does reactivity increase as you go down Group 1?
Reactivity increases because the outer electron gets further from the nucleus as more electron shells are added. This means the force of attraction between the nucleus and the outer electron becomes weaker, so less energy is needed to remove it and the metal reacts more easily.
When a Group 1 metal reacts, it .......... one electron to form a .......... ion, which has noble gas configuration.
When a Group 1 metal reacts, it loses one electron to form a 1+ ion, which has noble gas configuration.
What happens to a Group 1 atom when it loses its outer electron?
When a Group 1 atom loses its outer electron, the next shell down automatically becomes the outermost shell. Because this shell is already full, the ion has noble gas configuration, making it highly stable.
True or False?
Lithium is more reactive than potassium because it has fewer electron shells.
False.
Lithium is less reactive than potassium. Although lithium has fewer shells, its outer electron is closer to the nucleus and therefore held more strongly. More energy is needed to remove it, so lithium reacts less easily than potassium.
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