Group 1 (basics & trends)
What name is given to the elements in Group 1 of the periodic table?
The alkali metals.
When Group 1 metals react with water, which gas is produced?
Hydrogen.
What name is given to the elements in Group 7?
The halogens.
What charge does a halide ion have?
-1
How many electrons do Group 1 atoms have in their outer shell?
1
Name the first three Group 1 elements.
Lithium, sodium and potassium.
Complete the word equation:
alkali metal + water → __________ + hydrogen
Metal hydroxide.
Which Group 7 element is a red-brown liquid at room temperature?
Bromine.
What type of bond forms between sodium and chlorine in sodium chloride?
Ionic bond.
How many electrons do Group 7 atoms have in their outer shell?
7
Give two physical properties of Group 1 metals.
Any two: soft, low density, low melting point, shiny when freshly cut.
Write the balanced symbol equation for sodium reacting with water.
2Na + 2H₂O → 2NaOH + H₂
What does it mean when we say halogens are diatomic?
They exist as molecules made of two atoms joined together.
Complete the equation:
Cl₂ + 2KBr → ______ + ______
2KCl + Br₂
When Group 1 metals react, do they lose or gain electrons?
They lose electrons.
State the trend in reactivity down Group 1.
Reactivity increases down the group.
Describe one observation when potassium reacts with water.
Any one: vigorous reaction, moves very rapidly, fizzing, burns with a lilac flame, dissolves very quickly.
State two trends in the halogens as you go down Group 7.
Any two: colour gets darker, melting point increases, boiling point increases, physical state changes from gas to liquid to solid.
A student adds chlorine water to potassium iodide solution. What colour change would show a reaction has happened?
The solution turns brown because iodine is formed.
When halogens react, do they lose or gain electrons?
They gain electrons.
Predict two properties of rubidium based on its position below potassium in Group 1.
Any two: more reactive than potassium, softer than potassium, lower melting point than potassium, more dense than potassium.
Explain why potassium is more reactive than lithium.
Potassium has more electron shells, so its outer electron is further from the nucleus. The attraction between the nucleus and the outer electron is weaker, so the electron is lost more easily.
Explain why the melting and boiling points of the halogens increase down the group.
The molecules get larger down the group, so intermolecular forces become stronger. More energy is needed to overcome these forces.
Explain why bromine displaces iodine from potassium iodide, but iodine does not displace bromine from potassium bromide.
Bromine is more reactive than iodine, so bromine can gain electrons more easily and displace iodine. Iodine is less reactive, so it cannot displace bromine.
Compare the reactivity trends of Group 1 and Group 7 and explain both.
Group 1 becomes more reactive down the group because the outer electron is further from the nucleus and is lost more easily. Group 7 becomes less reactive down the group because the outer shell is further from the nucleus, so the attraction for a gained electron becomes weaker.