The atomic number of nitrogen is 7. The atomic mass is 14.01 amu. This means that___?

A.) A small percentage of nitrogen atoms have more than 7 neutrons

B) All nitrogen atoms have exactly 7 neutrons. 

C) Some nitrogen atoms have more than 7 neutrons. 

D) A small percentage of nitrogen atoms have fewer than 7 neutrons.

4 Answers

  • Dr W
    Lv 7
    2 months ago

    C is the correct choice.


    let's start here

    .. mass proton = 1.0073 amu

    .. mass neutron = 1.0087 amu

    .. mass electron = 0.00055 amu


      atomic mass = mass protons + mass neutrons + mass electrons - mass defect

    we can easily sum up the masses of protons + neutrons + electrons (in a neutral atom)... but.... we don't know mass defect


    So, the best way to solve this is to lookup the isotopic mass of N-14

    .. isotopic mass N-14 = 14.003 amu

    since the relative atomic mass = 14.01 that means some atoms of N will have more than 7 neutrons to increase the weighted average above 14.003

    now let's consider this example.  let's say we have 60% N-15 atoms and enough N-7 to N-12 atoms to bring the weighted average down to from 15.003 to 14.01.  meaning we can't say from this analysis that there is only a small percentage of N atoms with > 7 neutrons

    what we can say is there are at least SOME N atoms with # neutrons > 7


    although both (A) and (C) are correct in reality, there is only choice you can logically assume is correct... (C)

  • Anonymous
    3 months ago

    The answer is B, because there are no known isotopes of nitrogen.

  • 3 months ago

    none of the above.  it is possible to have both fewer than and more than 7 neutrons in a portion of the population.  The variation from ideal (the "ideal" being 14AMU) is not necessarily due to an excess of neutrons in a small portion of the population either.  Only 12C has exactly 12 AMU (by definition).

  • 3 months ago

    C) Some nitrogen atoms have more than 7 neutrons. 

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