Why Reactivity Increases Down Group 1
Part of Group 1: Alkali Metals — GCSE Chemistry
This how it works covers Why Reactivity Increases Down Group 1 within Group 1: Alkali Metals for GCSE Chemistry. Revise Group 1: Alkali Metals in Atomic Structure for GCSE Chemistry with 20 exam-style questions and 20 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 4 of 13 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 4 of 13
Practice
20 questions
Recall
20 flashcards
⚙️ Why Reactivity Increases Down Group 1
The key to understanding Group 1 reactivity lies in the concept of nuclear attraction and shielding. All Group 1 elements have one outer electron that must be lost to achieve a stable full outer shell configuration. In lithium (the smallest), this outer electron sits in the second shell, quite close to the positive nucleus — the attraction is relatively strong, making the electron harder to remove. In sodium, the outer electron is in the third shell, further away. In potassium, it is in the fourth shell, even further. As you go down the group, two things happen: the outer electron is further from the nucleus (weaker electrostatic attraction due to greater distance), and there are more inner electron shells between the outer electron and the nucleus — these inner shells repel the outer electron and reduce the pull of the nucleus on it (this effect is called electron shielding). Both factors make the outer electron easier to remove, so the element loses it more readily in reactions. Because the electron is released more easily, the metal reacts more rapidly with water — the reaction releases energy faster, which is why the fizzing is more vigorous and why potassium generates enough heat to ignite the hydrogen gas produced. This is why potassium reacts explosively with water while lithium only fizzes gently.