Lithium, sodium and potassium are metals in group 1 of the periodic table - Edexcel - GCSE Chemistry - Question 2 - 2012 - Paper 1

Lithium, sodium, and potassium are in group 1 of the periodic table because they each have one electron in their outer shell. This characteristic means they will readily lose this single electron during chemical reactions, making them highly reactive and categorizing them as alkali metals. The group number denotes the number of electrons in the outer shell, which in this case is consistently one across these elements.

When a small piece of potassium is added to water, you would observe effervescence or fizzing as hydrogen gas is released. The potassium would float on the surface of the water and react vigorously, producing heat. It may also create a lilac flame as it ignites, and eventually, it would dissolve.

The correct balanced equation for this reaction is D: 2K + 2H2O → 2KOH + H2. This indicates that potassium reacts with water to produce potassium hydroxide and hydrogen gas.