The Student Room Group

Element composition

If I know the name of an element for example: beryllium 11. How do I know the number of protons and neutrons?
Use a periodic table to find the atomic number of beryllium. The atomic number is the number of protons. The mass number is the sum of the protons and neutrons. If it's beryllium-11 then the mass number is 11, so you can use the number of protons to find the number of neutrons.
Original post by Tammie2345524
Use a periodic table to find the atomic number of beryllium. The atomic number is the number of protons. The mass number is the sum of the protons and neutrons. If it's beryllium-11 then the mass number is 11, so you can use the number of protons to find the number of neutrons.

does it matter if its an isotope. What if I know its 5 protons and 6 neutrons therefore a -1 charge
also can i minus from the atomic number or not?
A nucleus with 5 protons and 6 neutrons would have a charge of +5 (which is neutralised by the orbiting electrons, for an uncharged atom).

In general, there is no easy way to determine the ratio of neutrons (N) to protons (Z) given the total mass number (N+Z). For lighter elements, the ratio is 1:1, but for heavier elements it's more like 1:1.5. The reasons are complex and to do with way strong nuclear force acts between the nucleons.

(edited 2 years ago)
Original post by lordaxil
A nucleus with 5 protons and 6 neutrons would have a charge of +5 (which is neutralised by the orbiting electrons, for an uncharged atom).

In general, there is no easy way to determine the ratio of neutrons (N) to protons (Z) given the total mass number (N+Z). For lighter elements, the ratio is 1:1, but for heavier elements it's more like 1:1.5. The reasons are complex and to do with way strong nuclear force acts between the nucleons.


damn u smart.
Thanks - but it was you who asked the interesting question.

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