GCSE›Edexcel GCSE Chemistry›Mind mapsGroup 1Edexcel GCSE Chemistry: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsPhysical traitsSoft: cut with a knifeLow melting pointsMelting point decreases down the groupAtom and ions1 electron in the outer shellLose it to form 1+ ionsReaction with waterMetal + water → hydroxide + hydrogen2 Na+2 HX2O→2 NaOH+HX2\ce{2Na + 2H2O -> 2NaOH + H2}2Na+2HX2O2NaOH+HX2Float, move and fizzSodium melts into a ballPotassium: hydrogen ignites, lilac flameGroup 1the alkali metalsLiNaKRbCsReactivity trendReactivity increases down the groupLi < Na < KRubidium reacts more violently than potassiumWhy the trend?More shells down the groupOuter electron further from the nucleusMore shielded from the nucleusSo it is easier to loseExam tipsExplain with distance and shielding'More shells' alone does not scorePredict Rb and Cs as more violent