Chemists! periodic table atomic number question

[Rich1988]

Just a quick question for any of you chemistry wizzes, why is the atomic number sometimes top left, top right or center ? and are all three valid?

Thanks!

 

[dirtychinchilla]

It shouldn't be...look at this

 

[Rich1988]

Depending on which source you look at it the placing of it differs, always on top but sometimes either top left top center or top right

 

[MBennett]

Atomic number will always be the smaller of the two and always an integer. The Atomic mass includes neutrons and is a weighted average of all the isotopes commonly found and is not usually an integer. This should help you quickly identify which is which.

 

[Rich1988]

i know what the atomic number is just on different periodix tables it can be in different positions along the top. I asked a chemistry teacher and he said either top left or top right od the box is valid

 

[aardvark]

i dont think there is a rule - i've seen them all over the place.

 

[KingOfTheDaves]

Just to be different, I'm sure when I was in school, atomic number was on the bottom (left I think), and the atomic weight/mass was top left.