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| style="height:20px; width:200px; text-align:center;" |[[Lithium]] has seven [[nucleon]]s so it has an '''atomic mass''' of 7.
| style="height:20px; width:200px; text-align:center;" |[[Beryllium]] has nine [[nucleon]]s so it has an '''atomic mass''' of 9.
|}
==Key Stage 3==
===Meaning===
[[File:ElementTile.png|right|400px|thumb|An [[element]] tile showing the '''mass number'''.]]
The '''relative atomic mass''' or '''mass number''' of an [[element]] is the number of [[nucleon]]s ([[proton]]s + [[neutron]]s) in an [[atom]].
The '''relative atomic mass''' in [[gram]]s is also the [[mass]] of one [[mole]] or [[Avagadro Constant|6.02x10<sup>23</sup>]] [[atom]]s of the [[element]].
===About Relative Atomic Mass===
: The '''relative atomic mass''' in [[gram]]s on the [[Periodic Table]] tells the [[mass]] of a [[mole]] of the [[element]].
: A [[mole]] of the [[element]] is [[Avagadro Constant|6.02x10<sup>23</sup>]] [[atom]]s of that [[element]].
: Two [[atom]]s of the same [[element]] may have the same [[Atomic Number]] but a different [[Relative Atomic Mass]] depending on the number of [[neutron]]s in the [[nucleus]]. [[Element]]s with different '''mass numbers''' are called [[isotope]]s.
: The '''relative atomic mass''' is not affected by the number of [[electron]]s.
: Only the [[particle]]s in the [[nucleus]] affect the '''relative atomic mass'''.
===Examples===
{| class="wikitable"
| style="height:20px; width:200px; text-align:center;" |'''Hydrogen'''
| style="height:20px; width:200px; text-align:center;" |'''Helium'''
| style="height:20px; width:200px; text-align:center;" |'''Lithium'''
| style="height:20px; width:200px; text-align:center;" |'''Beryllium'''
|-
|[[File:Hydrogen.png|center|200px]]
|[[File:Helium.png|center|200px]]
|[[File:Lithium.png|center|200px]]
|[[File:Beryllium.png|center|200px]]
|-
|[[File:HydrogenSymbol.png|center|200px]]
|[[File:HeliumSymbol.png|center|200px]]
|[[File:LithiumSymbol.png|center|200px]]
|[[File:BerylliumSymbol.png|center|200px]]
|-
| style="height:20px; width:200px; text-align:center;" |[[Hydrogen]] has one [[nucleon]] so it has an '''atomic mass''' of 1 and [[Avagadro Constant|6.02x10<sup>23</sup>]] (or 1 [[mole]] of) [[atom]]s of [[Hydrogen]] have a [[mass]] of 1g.
| style="height:20px; width:200px; text-align:center;" |[[Helium]] has four [[nucleon]]s so it has an '''atomic mass''' of 4 and [[Avagadro Constant|6.02x10<sup>23</sup>]] (or 1 [[mole]] of) [[atom]]s of [[Helium]] have a [[mass]] of 4g.
| style="height:20px; width:200px; text-align:center;" |[[Lithium]] has seven [[nucleon]]s so it has an '''atomic mass''' of 7 and [[Avagadro Constant|6.02x10<sup>23</sup>]] (or 1 [[mole]] of) [[atom]]s of [[Lithium]] have a [[mass]] of 7g.
| style="height:20px; width:200px; text-align:center;" |[[Beryllium]] has nine [[nucleon]]s so it has an '''atomic mass''' of 9 and [[Avagadro Constant|6.02x10<sup>23</sup>]] (or 1 [[mole]] of) [[atom]]s of [[Beryllium]] have a [[mass]] of 9g.
|}