6.5 - Explaining alkali-metal reactivity
Explain why alkali metals have similar reactions but become more reactive down Group 1. Connect their electronic configurations to the attraction holding the outer electron in the atom.
One outer electron and similar reactions
An electronic configuration describes the arrangement of electrons in shells. Lithium, sodium and potassium each have one outer-shell electron:
| Atom | Electronic configuration | Occupied shells |
|---|---|---|
| lithium | 2,1 | 2 |
| sodium | 2,8,1 | 3 |
| potassium | 2,8,8,1 | 4 |
[DIAGRAM: asset_name: group1_electronic_configuration_reactivity: Group 1 electronic configuration and reactivity - diagram 1; asset_slug: 151_6_5_this_pattern_in_reactivity_in_terms_of_electronic_configurations_diagram1; file: 151_6_5_this_pattern_in_reactivity_in_terms_of_electronic_configurations_diagram1_imagegen_v1.png; recommended_method: imagegen; description: Exact monochrome teaching diagram for Pearson Edexcel 1CH0 6.5 showing lithium 2.1, sodium 2.8.1 and potassium 2.8.8.1 as shell diagrams with one outer electron, a downward arrow labelled more shells, more shielding and increasing reactivity, and notes that the outer electron is farther from the nucleus and lost more easily. Inner shells are labelled with electron totals; only the outer electron is drawn individually. The selected image has been checked for shell counts and trend direction.]
The diagram labels inner-shell electron totals rather than drawing every electron. Read the three atoms from left to right as examples progressively farther down Group 1; the vertical arrow indicates the group trend.
Each atom reacts by losing one outer electron to form a 1+ ion. The ion then has a full outer shell. For example, sodium changes from 2,8,1 to Na⁺ with configuration 2,8. The nucleus does not change: removing one negative electron leaves one more proton than electrons.
This shared outer-shell arrangement explains the similar reactions of the alkali metals.
Continue this lesson.
You’re previewing NovaLearn without an account. Create a free account to read the rest.
Create free account