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Mysara Juairia Chowdhury

Particle Physics: Why Protons are Positive and Neutrons are Neutral (Mathematical Proof)

Murray Gell-Mann and George Zweig, two independent physicists, first proposed the idea of smaller constituent particles called quarks in 1964. Quarks could be used to explain the strong interacting properties of hadrons. The two most famous hadrons we are familiar with are protons and neutrons - the very building blocks of our universe that make up atoms and matter as we see them.


In our science books, we were always taught that protons are positive, and neutrons are neutral. But how? How do they have these specific charges? To understand the charges of these particles, we must delve deeper to understand quark combinations.


In the table above, we can see quark particles (up, charm, top) with their +2/3 charge. They are paired with their opposite counterparts (down, strange and bottom) with charges -1/3 charge. These are called anti-quarks.


Proton Combination



Protons are composed of 2 up quarks and 1 down quark. This gives protons the combined charge of


Up+Up+Down

=(+2/3)+(+2/3)+(-1/3)

= +1 


Hence, protons have a positive charge.


Neutron Combination



Neutrons are composed of 1 up quark and 2 down quarks. This gives neutrons the combined charge of


Up+Down+Down

= (+2/3)+(-1/3)+(-1/3)

= 0


Hence, neutrons have no charge and are neutral.

Works Cited



Wikipedia Contributors (2024). Quark. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Quark [Accessed 28 Jul. 2024]. ‌

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