Decoding chemical formulae

Q1: Which elements are present in CaCO3?

Calcium and cobalt

Incorrect - new elements begin with a capital letter, so CaCO3 contains Ca, C and O.

Calcium, carbon and oxygen

Correct - well done!

Calcium, carbon and cobalt

Incorrect - new elements begin with a capital letter, so CaCO3 contains Ca, C and O.


Decoding chemical formulae

Q2: Which elements are present in AlF3?

Aluminium and Fluorine

Correct - well done!

Aluminium, Iodine and Fluorine

Incorrect - new elements begin with a capital letter, so AlF3contains Al and F.

Aluminium and Iodine

Incorrect - new elements begin with a capital letter, so AlF3contains Al and F.


Decoding Chemical Formulae

Q3: Which statement below best describes CH4?

4 Carbon and 4 hydrogen atoms

Incorrect - remember if there's no number next to an elements symbol you have to imagine there's a number 1.

4 Carbon and 1 hydrogen atoms

Incorrect - remember if there's no number next to an elements symbol you have to imagine there's a number 1.

1 Carbon and 4 hydrogen atoms

Well done!


Decoding chemical formulae

Q4: Which statement below best describes HNO3?

1 Hydrogen, 3 nitrogen and 3 oxygen atoms

Afraid not - remember that if there's no number next to an element you have to pretend that there is a one. So there's 1 nitrogen not 3.

1 Hydrogen, 1 nitrogen and 3 oxygen atoms

Well done!

3 Hydrogen, 3 nitrogen and 3 oxygen atoms

Incorrect - remember if there's no number next to an element's symbol you have to pretend that there's a one there. So in this care there is one hydrogen and 1 nitrogen.


Decoding Chemical Formulae

Q5: Which of these best describes Mg(NO3)2?

1 Magnesium, 1 nitrogen and 6 oxygen atoms.

Incorrect - the brackets muliply everything that's inside - so the nitrogen must be doubled as well.

1 Magnesium, 6 nitrogen and 6 oxygen atoms

Incorrect - there's one nitrogen inside the brackets as there is no number next to it. The brackets then multiply it by 2 to give 2 nitrogen atoms.

1 Magnesium, 2 nitrogen and 6 oxygen atoms.

Well done!
Return to The Top of The Page