Chemistry / Unit 2 Chem 0225 short lesson, about 20 seconds
Isotope Notation (Nuclear Symbol)
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The idea
Isotope notation writes an element's mass number as a left superscript before its symbol, naming that specific isotope of the element.
In practice
Magnesium-24, written 24Mg, has 12 protons like every magnesium atom, but exactly 12 neutrons, distinguishing it from 25Mg or 26Mg.
Where people slip
The atomic number, sometimes shown as a left subscript, is often dropped since the element symbol already fixes it.
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