you need
  • Periodic Table of Elements DIMendeleev.
Guide
1
Thanks to the ability to correctly calculate the number of protons , neutrons or electrons, it is possible to determine the valence of the chemical elements, as well as create e-formula.This will require only periodic system of chemical elements DIMendeleev, which is mandatory reference material.
2
Table D.Mendeleev divided into groups (arranged vertically), of which only eight, and for periods arranged horizontally.Each chemical element has its own serial number and relative atomic weight, which is indicated in each cell of the periodic table.The number of protons (p) and electrons (ē) is numerically the same as the serial number of the item.T
o determine the number of neutrons (n) must be on the relative atomic mass (Ar) subtract the number of the chemical element.
3
Example № 1. Calculate the number of protons , electrons and neutrons atom of a chemical element number 7.Himichesky item number 7 - is nitrogen (N).First, determine the number of protons (p).If the sequence number 7, so there will be 7 protons .Given that the number coincides with the number of negatively charged particles, electrons (ē) will also be 7. To determine the number of neutrons (n) of the relative atomic mass (Ar (N) = 14) Subtract the ordinal number of nitrogen (№ 7).Consequently, 14 - 7 = 7. In general terms, all the information is as follows: p = +7; ē = -7; n = 14-7 = 7.
4
Example № 2. Calculate the number of protons , electrons and neutrons atom of a chemical element number 20.Himichesky item number 20 - is a calcium (Ca).First, determine the number of protons (p).If the sequence number 20, therefore, will have 20 protons .Knowing that this number is equal to the number of negatively charged particles, electrons means (ē) will also be 20. To determine the number of neutrons (n) of the relative atomic mass (Ar (Ca) = 40) Subtract the ordinal number of calcium (№ 20).Consequently, the 40 - 20 = 20. In general terms, all the information is as follows: p = +20; ē = -20; n = 40-20 = 20.
5
Example № 3. Calculate the number of protons , electrons and neutrons atom of a chemical element number 33.Himichesky item number 33 - is arsenic (As).First, determine the number of protons (p).If the sequence number 33, then 33 is the proton.Given that the number coincides with the number of negatively charged particles, electrons (ē) will also be 33. To determine the number of neutrons (n) of the relative atomic mass (Ar (As) = 75) Subtract the ordinal number of nitrogen (№ 33).Consequently, the 75 - 33 = 42. In general terms, all the information is as follows: p = +33; ē = -33; n = 75 -33 = 42.