Calculate the mass of the 4He nucleus in atomic mass units by subtracting the ma

Question

Calculate the mass of the 4He nucleus in atomic mass units by subtracting the mass of two electrons from that of a neutral 4 He atom. (See Appendix D, and give four decimal places.) The procedure suggested for part (a) is theoretically incorrect because we have neglected the binding energy of the electrons. Given that the energy needed to pull both electrons far away from the nucleus is 80 eV, is the correct answer larger or smaller than implied by part (a), and by how much (in u)? In stating the mass of the nucleus, about how many significant figures can you give before this effect would show up?

Explanation / Answer

We have mass of electron me =0.000548579867 u mass of 4He atom is mHe = 4.002603 u then mass of 4He nucleus id 4.002603 u -2(0.000548579867u) = 4.001505840266 u
(b) Considering the binding energy of nucleus, the mass of thenucleus increases.
The increasing mass of nucleus is 80eV/c2 =(80eV)(1.6 * 10-19J/eV)/(3 *108m/s)2
= 14.22 * 10-35kg
= (14.22 * 10-35kg)/(1.66053886 *10-27kg/amu) = 0.00000856348 u mass of 4He atom is mHe = 4.002603 u then mass of 4He nucleus id 4.002603 u -2(0.000548579867u) = 4.001505840266 u
(b) Considering the binding energy of nucleus, the mass of thenucleus increases.
The increasing mass of nucleus is 80eV/c2 =(80eV)(1.6 * 10-19J/eV)/(3 *108m/s)2
= 14.22 * 10-35kg
= (14.22 * 10-35kg)/(1.66053886 *10-27kg/amu) = 0.00000856348 u

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.