Sample MCAT Question - Atomic Number and Protons
C-13 is an isotope of carbon and contains how many protons?
a) 6
b) 7
c) 12
d) 13
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Chemical Symbol
Atomic Number and Protons
The ‘Z’ in nuclear notation stands for atomic number, or the number of protons in the nucleus of the atom. Each proton has a mass of 1 atomic mass unit (amu) and a positive charge of 1.6 x 10-19 coulombs. The charge of a proton is known as the elementary charge and is written as ‘1 e‘ or, more commonly, simply as ‘+1’. Also, because the proton is the only charged subatomic particle located in the nucleus (neutrons have no charge), atomic number is equal to nuclear charge (the charge carried by the entire nucleus).
It is important to note that an element’s identity is defined in terms of its atomic number. Carbon atoms may have six, seven, or eight neutrons, but they always have six protons. Further, all atoms with six protons are carbon atoms. So, if you know an atom’s identity, you can determine its atomic number, and vice-versa.
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