KS3 · Chemistry

Group 1 and Group 2 metals

A metal you can cut with a knife, that floats, fizzes and — if it's potassium — flames lilac on water? The periodic table predicts it.

Chemistry · Periodic table

Read the periodic table like a map

Tap the Alkali (G1) lens and Group 1 lights up. Tap down that column: Li, Na, K, Rb. Then tap Mg and Sr to find Group 2 — and notice which row each one sits in.

SelectedNaSodium
Atomic no.11
Mass23.0
Group · Period1 · 3
TypeAlkali metal

Tap any cell to load its data into the panel. Tap a lens to highlight a chemical family.

Watch out: Reactivity climbs down a group. It does not climb along a period.

Chemistry · Reading the evidence

Three alkali metals, one tub of water

how vigorously each metal reacts with water

1 · Most vigorous3 · Least vigorous

  1. Sodium

    Floats, forms a sphere and fizzes. Can give a yellow-orange flame.

  2. Lithium

    Floats, forms a sphere and fizzes as hydrogen gas is made.

  3. Potassium

    Floats, forms a sphere and fizzes. Gives a lilac flame.

Chemistry · What is happening to the metal?

Dissolving or reacting?

A small piece of lithium is dropped into a bowl of water containing universal indicator, which starts off green. The metal floats and fizzes.

Which is closest to what you think is happening to the metal?
How sure are you?

Chemistry · Word equations

Two reactions, one pattern each

Write the word equation for lithium reacting with water, then for calcium reacting with dilute hydrochloric acid. You supply the product lines.

  1. Lithium is a Group 1 metal, so it reacts with water. What we start with goes on the left: lithium + water →The arrow means 'reacts to make'.
  2. missing step
Which line is step 2?

Predict, then check

Use the pattern you have just seen, not a guess.

Magnesium fizzes with dilute acid but shows very little reaction with water. Calcium, the next Group 2 metal down, fizzes more vigorously with dilute acid and fizzes visibly with water. Strontium is the next metal down again. What would you predict?

Chemistry · Group 1 against Group 2

Group 1: alkali metalsvsGroup 2: alkaline earth metals

Each row compares a Group 1 metal with the Group 2 metal in the same period, such as sodium and magnesium.

Focus

Reactivity

Group 1: alkali metals

More reactive

Group 2: alkaline earth metals

Less reactive

The insight

Same row, one group apart: Group 1 wins. This is the difference to remember first.

Hardness

Group 1: alkali metals

Soft — can be cut with a knife

Group 2: alkaline earth metals

Harder

Melting point

Group 1: alkali metals

Low

Group 2: alkaline earth metals

Higher

Density

Group 1: alkali metals

Low — they float on water

Group 2: alkaline earth metals

More dense

Where the name comes from

Group 1: alkali metals

Alkali metals: they react with water to form an alkaline solution

Group 2: alkaline earth metals

Alkaline earth metals: like the alkali metals, they produce an alkali when they react with water

Reaction studied

Group 1: alkali metals

With water

Group 2: alkaline earth metals

With dilute acid

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Find a metal on the table and you can predict how wildly it reacts.

What you need to know

  • A group is a column of the periodic table and a period is a row. Elements in the same group have similar properties, and those properties change gradually down the group.
  • Group 1 metals (the alkali metals) are soft, have low melting points and low densities, and react with water to make hydrogen gas and an alkaline metal hydroxide solution. Group 2 metals (the alkaline earth metals) react with dilute acid to make a salt and hydrogen.
  • Reactivity increases down Group 1 and down Group 2. In the same period, Group 1 metals are more reactive than Group 2 metals. Reactivity does not increase along a period.
  • Group 1 metals are stored in oil because they react with oxygen and water in the air.

The big picture

Where a metal sits on the periodic table predicts how it reacts: reactivity increases down Group 1 and down Group 2, and Group 1 metals are more reactive than Group 2 metals in the same period.

Key points

1Down a group the properties change gradually; across a period they do not follow the same pattern for reactivity.
2Alkali metals do not dissolve in water; they react with it, giving hydrogen and a soluble hydroxide that turns universal indicator blue.
3Compared with Group 1 metals in the same period, Group 2 metals are harder, have higher melting points, are more dense and are less reactive.
4Going down Group 1, melting and boiling points decrease and density generally increases.
5The table lets you predict: strontium, further down Group 2 than calcium, should react even more vigorously.

Worked example

Problem

Sodium (Na) and magnesium (Mg) are neighbours on the periodic table. Which is more reactive, and how can you tell without seeing either one react?

⚠ Watch out

Two slips catch people out: saying a Group 1 metal 'dissolves' in water (it reacts with it), and thinking reactivity increases as you move along a period (it increases down a group).

🧠

Memory hook

Down a group, the drama goes up. In the same row, Group 1 is the dramatic one and Group 2 is calmer.

✓

Check yourself

Rubidium sits directly below potassium in Group 1. Predict: more or less reactive with water than potassium? (More — reactivity increases down Group 1.)

Flashcards

(14)
Group or period: which is a column and which is a row?
A group is a column. A period is a row.
What do elements in the same group have in common?
Similar properties, which change gradually as you go down the group.
Which elements are the alkali metals, and why are they called that?
The Group 1 metals (lithium, sodium, potassium and those below them). They react with water to form an alkaline solution (pH greater than 7) and hydrogen gas.
What is an alkali?
A soluble base with a pH greater than 7.
Does a Group 1 metal dissolve in water?
No. It reacts with the water, making hydrogen gas and a soluble metal hydroxide.
Compared with most metals, how do Group 1 metals feel and behave physically?
They are soft (you can cut them with a knife), with low melting points and low densities, so they float on water. All are solids at room temperature.
In which direction does reactivity increase in Groups 1 and 2?
Down the group — not along a period.
How do Group 2 metals compare with the Group 1 metal in the same period?
Harder, higher melting point, more dense and less reactive.
How do melting point and density change down Group 1?
Melting and boiling points decrease. Density generally increases (a broad trend).
Why are Group 1 metals stored in oil?
They react with oxygen and water in the air.
What flame colours can sodium and potassium give in water?
Sodium can give a yellow-orange flame. Potassium, which is much more reactive, gives a lilac flame.
Why are Group 2 metals called alkaline earth metals?
Like the alkali metals, they produce an alkali when they react with water.
What do Group 2 metals make when they react with dilute acid?
A salt and hydrogen gas (metal + acid → salt + hydrogen).
What does universal indicator do when a Group 1 metal reacts with water?
It turns from green to blue, because a soluble metal hydroxide makes the solution alkaline.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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