Radicals

atom.gif (1130 bytes) Radicals

A Radical is a charged group of atoms. Radicals often remain grouped together during chemical reactions. Radicals have a valency in the same way that ions have a valency. Some of the common Radicals are listed below.

-1	-2
Nitrate NO3 - bicarbonate HCO3 - Hydroxide OH-	Carbonate CO3 -- Sulfate SO4 -- (or sulphate)

When working out the formula of compounds containing radicals just think of the radical as a single unit as if it is an ordinary ion.

Consider Calcium Nitrate ...

The Nitrate radical is treated as if it is a single ion. The 'bracket' is placed around the radical for clarity. If you were working out the number of atoms in one molecule of Calcium Nitrate you need to remember that the '2' outside the bracket means two radicals of Nitrate which means two of everything inside the bracket.

calciumnitrate.gif (5957 bytes)

ie Calcium Nitrate consists of: 1 atom of Calcium, 2 atoms of Nitrogen and 6 atoms of Oxygen.

Other examples ...

Compound	Formula	Composition of one Molecule of the Substance
Magnesium bicarbonate	Mg(HCO3)2	1 Magnesium atom, 2 Hydrogen atoms, 2 Carbon atoms, 6 Oxygen atoms
Aluminium Sulfate	Al2(SO4)3	2 atoms of Aluminium, 3 atoms of Sulfur, 12 atoms of Oxygen

NOTE: You MUST become confident in writing formulae and working out the number of atoms of elements in a molecule from its formula. If you are not, you will never be able to balance chemical equations.

Make sure you understand the previous sections.
Make sure you have memorised the valencies of the common ions and radicals.

Radicals - QUIZ

Your Name and School -

Do you Certify the answers below to be all your own work? -

1. What is the difference between an "ion" and a "radical"? Give an example of each. -

2. An imaginary radical is represented by: X3BZ2 +. What does this tell us?-

3. Write the formulae for: Calcium Hydroxide, Sodium Sulfate, Barium Nitrate? -

4. How many Hydrogen atoms are in one molecule of Aluminium bicarbonate - Al(HCO3)3?

5. What is the chemical name of: Na2SO4, CaCO3, Cu(HCO3)2?

6. What is the chemical name of: H2SO4, HNO3?

7. What is the valency of C in CO2 - explain?

8. What is the URL of a Web page containing information about radicals (apart from this one)?

Feedback, comments, questions -

(Make sure your NAME and SCHOOL are included.)

This form will be emailed to a 'marker'. You will receive feedback shortly. Satisfactory performance on this and other Quizzes is required for the granting of a "Completion Certificate" for this Course.