Deducing Formulae of Compounds

Question 1

Ionic compounds are electrically neutral the what charges equal each other

Answer 1

the positive charges equal the negative charges

Question 2

The charge on the ions of the transition elements can vary which is why ………………….are often used to indicate their charge

…………are used in some compounds formed from transition elements to show the charge (or oxidation state) of metal ions
E.g.

Answer 2

Roman numerals

in copper (II) oxide, the copper ion has a charge of 2+ whereas in copper (I) nitrate, the copper has a charge of 1+

Question 3

The non-metals in group 15 to 17 have a negative charge and have the suffix ‘ide’

E.g. nitride, chloride, bromide, iodide
Elements in group 17 gain 1 electron so have a 1- charge, eg. Br-
Elements in group 16 gain 2 electrons so have a 2- charge, eg. O2-
Elements in group 15 gain 3 electrons so have a 3- charge, eg. N3-

Question 4

There are also polyatomic negative ions, which are

Answer 4

negative ions made up of more than one type of atom

Polyatomic ions are ions that contain more than one type of element, such as OH-

Question 5

During chemical reactions, atoms cannot be

Answer 5

created or destroyed
The number of each atom on each side of the reaction must therefore be the same
E.g. the reaction needs to be balanced

Question 6

In combustion reactions how what should you remember

Answer 6

To put the numbers used to balance the equation in front of the formulae

To balance firstly the carbon, then the hydrogen and finally the oxygen in combustion reactions of organic compounds

Question 7

ALSO USE APPROPRIATE STATE SYMBOLS IN BALANCED EQUATION