Chemistry · Semester B TEKS 14A-14C
HardCalc
Write the balanced nuclear equation for the beta-minus decay of carbon-14, explaining why atomic number increases even though no protons are directly 'added' from outside the nucleus.
A¹⁴₆C → ¹⁴₇N + ⁰₋₁e — a neutron converts to a proton (raising atomic number by 1) while mass number stays the same
B¹⁴₆C → ¹⁴₆N + ⁰₋₁e, keeping the atomic number unchanged despite beta decay's neutron-to-proton conversion
C¹⁴₆C → ¹³₇N + ⁰₋₁e, incorrectly decreasing the mass number by 1 during a process that actually conserves it
D¹⁴₆C → ¹⁴₅B + ⁰₋₁e, describing beta-minus decay as the loss of a proton rather than the gain of one
Explanation
Beta-minus decay occurs when a neutron inside the nucleus converts into a proton, an electron (the emitted beta particle, ⁰₋₁e), and an antineutrino (often omitted in introductory equations) — since a neutron becomes a proton, atomic number increases by 1 even though no particle is added from outside, and mass number stays the same because a neutron (mass number contribution of 1) is simply replaced by a proton (also mass number contribution of 1) within the nucleus. For carbon-14: ¹⁴₆C → ¹⁴₇N + ⁰₋₁e, with nitrogen (atomic number 7) as the daughter. Writing the daughter as having the SAME atomic number as carbon (6) misses that beta decay specifically changes a neutron into a proton, increasing atomic number. Writing the mass number as decreasing to 13 misunderstands that beta decay conserves mass number, since a neutron converting to a proton doesn't remove a nucleon from the nucleus, only changes its type. Describing beta-minus decay as the loss of a proton from the nucleus (rather than the gain of one, via neutron-to-proton conversion) reverses the actual particle-level mechanism.
¿Listo para empezar a practicar?
Free sample questions available. No credit card required.
More Chemistry practice
Image · TEKS 6A-7D
Based on VSEPR theory, which of the following best describes the shape of the methane molecule (CH₄) shown below?
Word Problem · TEKS 14A-14C
A radioactive sample decays from 100.0 g to 12.5 g over exactly 21.6 days, with no half-life value given directly....
Word Problem · TEKS 14A-14C
Helium-4's actual measured mass is 4.002602 amu. It is built from 2 protons and 2 neutrons — using the mass of a...
Word Problem · TEKS 14A-14C
Uranium-238 decays (through a long series of steps) to lead-206, with an overall effective half-life of 4.47 billion...