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Average Atomic Mass
Average Atomic Mass
On the periodic table, the atomic symbol looks a little different:
6.938 is the average atomic mass of Lithium! It represents the abundance of different lithium isotopes on earth. Keep in mind average atomic mass and atomic mass are different.
The 3 is Lithium's atomic number.
This average is based on the weight of the isotope and how abundant each isotope is on Earth (percentage-wise). For example:
5.85% of the iron on Earth is iron-54
91.75% of the iron on Earth is iron-56
2.12% of the iron on Earth is iron-57
0.28% of the iron on Earth is iron-58
Together these average out to 55.847!
To average the numbers and find the value on the table, we take each mass, multiply them by their abundance, and divide the total by 100. For iron:
((5.85 x 54) + (91.75 x 56) + (2.12 x 57) + (0.28 x 58))/100
= 55.847
Rounding messed the number up a bit, but it's close enough!
Energy Levels
Energy Levels
When an atom gains energy, they become excited, with electrons move to higher energy locations surrounding the nucleus, further away from the center of it. They don't stay there for long though; these electrons jump back down to their original location (aka the ground state), releasing energy in the form of electromagnetic waves (aka light waves). Each type of atom has their own combination of light waves released in this way, allowing us to use a prism or flame test to determine what elements are in something. This process of determining what something is based on the light it emits is known as spectroscopy.
Additional Resources
Additional Resources
Interesting Links
Interesting Links
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