Question

Study the information in the table below and answer the questions that follow: The letters do not represent the actual symbol of the element).

Element	Electronic configuration	Ionisation energy KJ mol−1
P   Q   R	2,1      2,8,1      2,8,8,1	519           494           418

1. What is the general name given to the group in which element P, Q and R belong? 
2. What is meant by ionization energy 
3. Explain why Element P has the highest ionization energy 
4. When a piece of element Q is placed on water it melts and a hissing sound is produced as it moves on the surface of the water .Explain this observation 
5. Write an equation for the reaction between elements Q and water 

Answer 1

1. Alkali metals
2. Energy required to remove an electron from an atom or molecule.
3. P has the smallest atomic radius and therefore the valency electron is most strongly attracted to the nucleus.
4.  
   1. Melts due to heat produced in the reaction.
   2. Hissing sound due to the production of hydrogen.
   3. Floats on water, sodium is less dense than water.
5. 2Q(s) + 2H₂O(l) → 2QOH(aq) + H₂(g)
   or
   2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)