1. BellWork 2/16/2015 Mg2+ Cl- Fe2+ O2-
These elements are written to describe what? Grab a textbook and look it up if needed.

2. What are Isotopes
Isotopes are atoms that have a different number of neutrons.
An atom is still the same element if it has different neutrons - it’s just a different version!
Neutrons can be added to an atom without altering the number of protons and electrons it has.

3. Carbon Isotopes
For example, the element carbon has 13 different isotopes!
You are familiar with C-12 (the C stands for carbon, and the 12 is it’s atomic mass)
This isotope has 6 neutrons
C-14 (atomic mass 14) is used for carbon dating and has 8 neutrons!

4. More about Isotopes
In an isotope, the number of protons and electrons never changes- only the number of neutrons is different
This means that each isotope of a particular element has a different atomic mass than another isotope of the same element
Remember: C-12 has an atomic mass of 12 and C- 14 has an atomic mass of 14!

5. Isotope Notation
There are several different ways to write symbols for isotopes, each of which is perfectly legitimate.
The other ways to write each of these hydrogen isotopes from top to bottom are:
Hydrogen-1 or H-1
Hydrogen-2 or H-2
Hydrogen-3 or H-3
Example
Write down the three different notations for a carbon atom with 6 protons and 6 neutrons.

6. Quick Activity
Calculate the number of neutrons there are in the following isotopes (use your periodic table to find the atomic numbers)
Carbon-14
Nitrogen-15
Sulfur-35
Calcium-45
Iodine-131