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How Many Protons Are in Potassium?



An atom of potassium contains 19 protons.

Periodic Table Math

The first step is to identify an element’s atomic number on the Periodic Element Table. This number corresponds to the number of protons in that same, given element. So for Potassium, or K, the atomic number is 19. That is in fact, from left-to-right, sequentially how elements are ranked on the Periodic Table. By ascending order of their atomic number.

At a quick glance, a person can eyeball where an element ranks overall in terms of its proton mass. The lowest such element is hydrogen, which has an atomic number of one. At the other end of the Periodic Table spectrum is krypton, which has the much larger atomic number of 118.

Electrons, Neutrons

Since by definition, an atom has no overall electronic charge, the number of electrons must be the same as the number of protons. So in the case of potassium, there are 19 protons as well as 19 electrons.

The number of neutrons contained in potassium is a little more complicated. This is not summarily listed on the Periodic Table but can be easily derived by looking at the other number on the chart, an element’s atomic weight. Rounded down, it is 39 for potassium. By subtracting the number of protons or electrons from that number (in this case, 19), the total remaining is the number of neutrons. So for potassium, 19 taken away from 39 leaves 20 neutrons.

People rarely look at the world around them in atomic terms, unless perhaps they are scientists. But at that minute, molecular level, all these different combinations of neutrons, electrons and protons combine to make every single bit of matter in a room or open air environment. The only difference is that in the case of potassium, it is not naturally prevalent. Unlike say oxygen or hydrogen, it is not naturally prevalent.



Haynes, William M.., and David R. Lide. CRC Handbook of Chemistry and Physics. 91th ed. Boca Raton (Fla.): CRC Press, 2010. Print.

“Sir Humphry Davy.” Encyclopedia of World Biography. 2004. 11 Feb. 2011 <>.

Times of India – “UAS to Host 2-Day Symposium on Potassium”, January 15, 2011, Retrieved February 9, 2011 from

Russia and India Report – “The Making of a Fertilizer Empire”, February 7, 2011, Retrieved February 9, 2011 from

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