What are the properties and trends of Group 1 elements? All pupils will be able to (Baseline): Describe how properties of the elements in Group 1 depend on the outer shell of electrons of the atoms. Most pupils will be able to (Further): Explain how properties of the elements in Group 1 depend on the outer shell of electrons of the atoms. Some pupils will be able to (Challenge): Predict properties from given trends down the group.

Your Task as you watch: You will need to fill in your sheet with the information that we discover as we see the alkali metals demonstration. We will discuss the equations section at the end. You will need to predict what the reaction for Rb would be using this data.

? Equations: Lithium What were your reactants? What were the products formed? Fill in the equation with what we know: ? Lithium(s) + Water(l) Hydrogen(g) +

Symbol Equation: Lithium ? Lithium(s) + Water(l) Hydrogen(g) + Li(s) + H2O(l) H2(g) + LiOH(aq) 2 2 2 Now complete the equations for the other Alkali Metals

Rubidium Physical Properties: Reactivity with water? Products formed? Very soft, relatively low melting point, shiny when cut. Reactivity with water? Very vigorous Products formed? Hydrogen gas and Rubidium Hydroxide Word Equation (Reaction of Rubidium and water) Rubidium(s) + Water(l) Hydrogen(g) + Rubidium Hydroxide (aq) Symbol Equation (Reaction of Rubidium and water) 2Rb + 2H2O 2H2 + 2RbOH

https://www. youtube. com/watch https://www.youtube.com/watch?v=m55k gyApYrY Rb, Cs braniac science (warning: it says ‘the dogs nuts’ in it) Alkali metals in water, accurate! (2:21min) Use this if not doing the demo. Episodes: Group 1 as an example of Groups in the periodic table (2:30 min) Trends in periodic table

The Patterns in the Periodic Table What are the patterns in the Alkali Metals? Reactivity Increases Li Na Melting and Boiling Point Decreases K Discovering this allowed us to explain some of the properties in Group 1. Rb Size of the atom increases Cs Fr

Reactivity The alkali metals have one too many electrons – they want to get rid of the one on the outer shell The electron is kept here because the nucleus in the middle has a large positive charge and attracts it in You could ask them to name the atom from the electron structure

Distance As you move down Group 1 the distance the electron the metal wants to get rid of is away from the big positive – the source of its attraction - gets further ….the attraction fades Li What is happening to the size of the atom here? Na A T R C I O N K Rb Cs Fr

Shielding The electron is attracted to the nucleus as it has an opposite charge. However, if there are electrons on inner shells then these “shield” the outer electrons from the positive charge of the nucleus. This means that the outer electrons attraction to the nucleus is even lower the more shells there are.

What does this mean for reactivity? Li Very Slow Na Slow K Medium Rb Fast Cs Very Fast The easier an electron leaves the more reactive the metal is!!

Past Exam Question (1)    These are the electronic structures of the atoms of three different elements. 2.8.1                     2.8.8                        2.8.8.1 element A             element B                element C (a)     Identify elements A and B.          Element A is ...............................          Element B is ............................... (b) (i) Why is element C more reactive than element A? (ii)     Why is element B unreactive?

Answers 1. (a) A is sodium/Na* B is argon/Ar* each for 1 mark (*case of letters must be correct) (b) (i) • outer electron (in element C / 2.8.8.1 / potassium) is at a higher energy level / in a more outer shell/further away from nucleus / shielded by more full electron shells • electron is more easily lost/less strongly held / attracted each for 1 mark (ii) • (element B / 2.8.8 / argon) has an outer shell that is complete/has 8 electrons • no tendency to gain or lose electrons / has a stable configuration • (not ‘is stable’ / ‘in group O’ / ‘a noble gas’) [6]