Chapter 2 - Atoms, Ions and Compounds

Define relative atomic mass

Relative atomic mass is the weighted mean mass of an atom of an element relative to 1/12th of the mass of an atom of carbon-12.

Formula for relative atomic mass

Define relative isotopic mass

The mass of an isotope relative to 1/12th of the mass of an atom of carbon-12.

Describe the basic principle of a mass spectrometer

1 A sample is placed in the mass spectrometer.

2 The sample is vaporised and then ionised to form positive ions.

3 The ions are accelerated. Heavier ions move more slowly and are more difficult to deflect than lighter ions, so the ions of each isotope are separated.

4 The ions are detected on a mass spectrum as a mass-to-charge ratio m/z. Each ion reaching the detector adds to the signal, so the greater the abundance, the larger the signal.

Formula for mass to charge ratio

Define polyatomic ions

Ions containing atoms of more than one element bonded together

Define binary compound

Compound containing two elements. Name it by using the first element’s name and changing the ending of the second element’s name to -ide.

Common polyatomic ions to memorise:

-Ammonium

-Hydroxide

-Nitrate

-Nitrite

-Hydrogencarbonate

-Manganate (VII) (Permanganate)

-Carbonate

-Sulfate

-Sulfite

-Dichromate(VI)

-Phosphate