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 ):

so

protons: 19, neutrons 20,

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

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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

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  • 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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