j asked in Science & MathematicsChemistry · 9 years ago

help me with chemistry finding the # of electrons given the protons & neutrons?

so yeah i took chemistry two years ago and forgot how to do it ):


protons: 19, neutrons 20,

what is the number of electrons? the mass (amu)? and the element?


20 neutrons, 40 amu, what is the number of protons? of neutrons? thanks!!!

this two examples should help me with most of my other hw problems. (((:

1 Answer

  • 9 years ago
    Best Answer

    The number of protons and electrons are always equal, and the number of the element = the number of protons. So Carbon is the 6th element, so it has 6 protons (and electrons). If you are given the mass number of say Carbon 15, to find the number of neutrons you subtract 6 (the element number and/or the number of protons) from 15 to get an answer of 9 neutrons.

    19 protons is the 19th element, Potassium. If you have 20 neutrons, then 19 + 20 = 39 amu.

    20 neutrons, 40 amu is 40 - 20 = 20 protons, or Calcium.

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