you need
  • - periodic table of chemical elements;
  • - proton charge;
  • - refer to chemical elements.
Guide
1
Each atom of matter corresponds to an element of the periodic table.Find an element of atomic number protons and neutrons in the nucleus to be found.Determine the atomic weight of that element.It is located at the bottom of the cell, where the chemical element.If the mass number represented a fractional value, round it up to integers.It number will be equal to the number of nucleons in the atom.For example, define the atomic mass of magnesium.Find the element in the periodic table, it is designated as Mg.Its mass equal number 24.305.Round it u
p to the whole, and get 24. This means that the number of protons and neutrons (nucleons) in the nucleus of an atom of this element is 24.
2
Determine the number of protons in the nucleus of an atom.To do this, locate it in the periodic table of chemical elements.At the top of the cell element marked by its serial number in a row in the table.This is the number of protons in the nucleus of an atom of an element.For example, the serial number of the magnesium (Mg) is equal to 12. This means that in its core contains 12 protons .
3
sometimes known only to the charge of the nucleus in the pendant, then, to find the number of protons , divide this number on the charge of the proton, which is equal to 1,6022 • 10 ^ -19 Coulomb.For example, if you know that the nuclear charge is 35,2 • 10 ^ -19 Coulomb, then dividing it by 1,6022 • 10 ^ -19 get number , approximately equal to 22. This means that in the nucleus of an atom is 2proton.
4
After determining the number of protons find the number of neutrons in the nucleus.To do this, the relative atomic mass of the nucleus, found with the help of the periodic table of chemical elements, subtract the number of protons , contained in the nucleus.Because in addition to neutrons other heavy particles in the nucleus of an atom is not contained, it will number of neutrons.For example, if you want to find the number of protons and neutrons in the nucleus of phosphorus (P), locate it in the periodic table, determine the mass number and serial number of the item.Mass number phosphorus equal 30,97376≈31, and the serial number 15. This means that the nucleus of an atom of a chemical element that contains 15 protons and 31-15 = 16 neutrons.