# GS103, quiz 3, answer key

1. The atomic mass of an element is A) the average atomic mass of its isotopes according to their proportions in nature.

2. A beam of light whose waves are all in step with one another is said to be A) coherent.

3. When a nucleus of the copper isotope  captures an electron, it becomes negatively charged!

4. The largest number of elements are classed as A) metals.

5. The half-life of a certain radioactive isotope is 6 h. If we start out with 10 g of the isotope, after 1 day there will be B) 0.625 g left.

6. A method of compressing fuel for a nuclear fusion reactor that is not being studied uses A) laser beams.

7. Which of the following electron jumps in a hydrogen atom emits the photon of highest frequency? B) n = 2 to n = 1

8. Most known nuclides A) are stable.

9. An X-ray photon has an energy of $3.3*10^15 J$ and Planck’s constant is 6.6 X 10-34 Js. The frequency that corresponds to this energy is D) $3.3*10^20$ Hz.

10. Potassium forms K+ ions and sulfur forms S2- ions. The formula of potassium sulfide is B) K2S.

11. The quantum number n of the lowest energy state of a hydrogen atom A) is 0.

13. The product of the alpha decay of the polonium isotope  is Pb  (lead)

14. Planck’s constant is $6.6*10^{-34}$ Js and the electron mass is $9.1*10^{-31} kg$. The de Broglie wavelength of an electron whose speed is $2.0*10^7 m$/s is C) $3.6*10^{-11} m$.

15. The most active of the following nonmetals is C) chlorine.

16. The metals most difficult to extract from their ores in general A) are the least active chemically.

17. According to the uncertainty principle, it is impossible to precisely determine D) both the position and the momentum of a particle.

18. The most abundant element in the universe is A) hydrogen.

19. Each horizontal row of the periodic table includes elements with chemical characteristics that are, in general B) similar.

20. All known charged particles have electric charges that are multiples of  e except for D) quarks