Atomic Structure and Isotopes

An Atomic Notation is a shorthand way of writing the structure of the atom showing the atomic number, atomic mass and the atomic symbol

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What is an Atomic Notation?

The nucleus of an atom contains protons and neutrons.

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The nucleus of the atom

Adding up all the protons and neutrons in the nucleus gives us the atomic mass

# of protons + # of neutrons = Atomic Mass

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The nucleus of the atom

Isotopes are atoms that have the same number of protons and electrons, but a different number of neutrons.


The number of neutrons can change leading to ISOTPES of that element.

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What are Isotopes?

Changing the number of neutrons changes the mass of the element


Isotopes are identified by their mass, which is the total number of protons and neutrons.

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What are Isotopes?

There are two ways that isotopes are generally written.

The first way is to put the mass as a superscript before the symbol of the element:

Naming Isotopes

The second way is to write out the element name and then write the mass after a dash next to the element's name:

Naming Isotopes

Hydrogen is the only elements whose isotopes have specific name

Hydrogen's Isotopes

All elements have a number of isotopes. Hydrogen has the fewest with 3.

Cesium and Xenon has the most isotopes with 36.

How many isotopes can an element have?