The Group 1 Elements

There are six elements in group 1 of the periodic table and they are:

  • Lithium
  • Sodium
  • Potassium
  • Rubidium
  • Caesium
  • Francium

You can see them in the first column of the periodic table - below:

 

All these elements have just one electron in the very outside layer of the electrons that surround the nucleus.

The elements in group 1 are often called the alkali metals.

Hydrogen is an element with only one electron on the outside - but it is a bit special so it is often drawn on its own.

   

    H            He
LiBe          BCNOFNe
NaMg          AlSiPSClAr
KCaScTiVCrMnFeCoNiCuZnGaGeAsSeBrKr
RbSrYZrNbMoTcRuRhPdAgCdInSnSbTeIXe
CsBaLaHfTaWReOsIrPtAuHgTlPbBiPoAtRn
FrRaAc               

 

Now answer these questions ... (write all numbers)

  1. How many different elements are shown in this periodic table ?
  2. How many of these elements are in Group 1 ?
  3. How many electrons do the Group 1 elements have in their outer shell ?
  4. Do each of the elements in Group 1 have the same or different numbers of electrons ?
  5. Which element is sometimes put in Group 1 - because it has only one electron ?
  6. What element has the chemical symbol, Na ?
  7. What element has the chemical symbol, K ?
  8. What element has the chemical symbol, Li ?
  9. What is the chemical symbol for Caesium ?
  10. The elements in Group 1 are sometimes also called what ? metals

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Why are the Group 1 Elements so Reactive ?

The first three elements in Group 1 are Lithium, Sodium and Potassium and the three pictures below show the arrangement of electrons in their atoms.

They have all got one electron in the outside shell even though they all have a different number of electrons in total. If you compare these pictures with the periodic table, above, you might notice that the elements have more electrons as you go down the the group.

Lithium

Lithium

Sodium

Sodium

Potassium

Potassium

These elements are very reactive - they will even react (causing an explosion) with water.

The reason why they are so reactive is that the elements are desperate to get rid of that single, untidy electron in the outer shell, and the bigger the atom is - the more it wants to get rid of the electron.

This means that the atoms get bigger as you go down the group and they also become more reactive (and more dangerous).
So, sodium is more reactive than lithium and potassium is more reactive than both of them.

 

... and now answer these questions (write all numbers)

  1. Do all atoms have the same number of electrons ?
  2. How many electrons does lithium have altogether ?
  3. How many electrons does sodium have altogether ?
  4. How many electrons does potassium have altogether ?
  5. How many electrons do these atoms have in their outer shell ?
  6. Out of sodium, potassium and lithium - which has the most electrons ?
  7. Out of sodium, potassium and lithium - which is the biggest ?
  8. Out of sodium, potassium and lithium - which is the most reactive ?
  9. Do atoms get bigger or smaller as you go down a group ?
  10. Do atoms get more or less reactive as you go down a group ?

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