Noble gases, the alkali metals and the halogens: their trends, displacement reactions, and how transition metals compare.
What you will learn
- Explain the reactivity trends in Groups 1 and 7
- Predict halogen displacement reactions
- Estimate a property from a trend
Group 0 and Group 1
Group 0 (noble gases) have full outer shells, so they are unreactive.
Boiling points rise down the group.
Group 1 (alkali metals) have one outer electron, which they lose to form 1+ ions. With water they fizz, float and form a metal hydroxide and hydrogen:
sodium + water → sodium hydroxide + hydrogen
2Na + 2H₂O → 2NaOH + H₂
Reactivity increases down the group: the outer electron is further from the nucleus and more shielded, so it is lost more easily.
Melting and boiling points fall down Group 1 (lithium melts at 181 °C, potassium at 63 °C).
To estimate a missing value in a group, use the trend: for an element between two others, take the mean of the values either side; for one at the end, carry the pattern on.
- Group 0 boiling points: neon −246 °C, argon ?, krypton −153 °C
- estimate for argon = (−246 + −153) ÷ 2 = −199.5 °C (the measured value is −186 °C)
The rest of this lesson and its 17 practice questions are locked.
In this lesson
- Group 0 and Group 1
- Group 7
- Transition metals (Chemistry only)
17 practice questions, marked as you go; about 25 minutes in all.
Key terms
Increases, Fall, Decreases, Displaces, Transition metals, Catalyst
In this unit: Atomic structure and the periodic table
Atoms, formulae and equations, separating mixtures, the model of the atom, isotopes, electrons in shells and the groups of the periodic table.