If an isotope of uranium, uranium-235, has 92 protons how many protons does the isotope uranium-238 have? Why?

2 Answers

  • 9 years ago
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    U238 also has 92 protons.

    Any variety of uranium will.

    If it had different from 92, it would not be uranium; if it has 92 it is uranium.

    mnemonic: isotoPe where the capitalized P means there are the same [iso] number of Protons

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  • 9 years ago

    Atoms are made up of protons, neutrons and electrons. The mass of a proton and neutron can be said to equal 1, whereas the mass an electron contributes to the atom is negligible (effectively 0).

    If uranium-235 has 92 protons, it has 143 neutrons to make one atom of U-235.

    An isotope of an element is one with the same chemical identity (therefore proton number is equal) but can have a varying mass. Since the proton number is equal, the difference in mass can only arise by a varying number of neutrons.

    Therefore Uranium-238 has 92 protons and 146 neutrons, making one atom.

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