Question

1. an isotope has an atomic number 51 and a mass number 123. answer the following question. 17. which of the isotopes in problems 13 - 16 are isotopes of the same element? identify the element. write each isotope below in symbolic notation. use the periodic table to determine the atomic number of each isotope. 18. neon - 22 10 19. helium 2 20. cesium - 133 21. uranium - 234 label the mass number and the atomic number on the following isotope notation. 22. 23. $_{12}^{24}mg$ in your textbook, read about mass of individual atoms. circle the letter of the choice that best completes the statement. 24. the mass of an electron is a. smaller than the mass of a proton. b. smaller than the mass of a neutron. c. a tiny fraction of the mass of an atom. d. all of the above. 25. one atomic mass unit is a. 1/12 the mass of a carbon - 12 atom. b. 1/16 the mass of an oxygen - 16 atom. c. exactly the mass of one proton. d. approximately the mass of one proton plus one neutron. 26. the atomic mass of an atom is usually not a whole number because it accounts for: a. only the relative abundance of the atoms isotopes. b. only the mass of each of the atoms isotopes. c. the mass of the atoms electrons. d. both the relative abundance and the mass of each of the atoms isotopes.

Explanation:

Step1: Recall atomic structure facts

Electrons have much less mass than protons and neutrons, and their mass is a tiny fraction of the atom's mass. So for question 24, the answer is d. all of the above.

Step2: Recall atomic mass unit definition

One atomic mass unit is defined as 1/12 the mass of a carbon - 12 atom. So for question 25, the answer is a. 1/12 the mass of a carbon - 12 atom.

Step3: Recall atomic mass concept

The atomic mass of an atom is usually not a whole number because it accounts for both the relative abundance and the mass of each of the atom's isotopes. So for question 26, the answer is d. both the relative abundance and the mass of each of the atom's isotopes.

Step4: Isotope symbolic notation

For neon - 22, the atomic number of neon is 10, and the mass number is 22. The symbolic notation is $_{10}^{22}Ne$.
For helium, the atomic number is 2 and common helium has a mass number of 4. The symbolic notation is $_{2}^{4}He$.
For cesium - 133, the atomic number of cesium is 55, and the mass number is 133. The symbolic notation is $_{55}^{133}Cs$.
For uranium - 234, the atomic number of uranium is 92, and the mass number is 234. The symbolic notation is $_{92}^{234}U$.

Step5: Isotope identification

Isotopes of the same element have the same atomic number. Without information about problems 13 - 15, we can't fully answer question 17. But if we only consider problem 16 with atomic number 51 (antimony), we need to compare with other isotopes in 13 - 15 by their atomic numbers to identify if they are of the same element.
For $_{12}^{24}Mg$, the atomic number is 12 (bottom number) and the mass number is 24 (top number).

Answer:

1. d. all of the above
2. a. 1/12 the mass of a carbon - 12 atom
3. d. both the relative abundance and the mass of each of the atom's isotopes
4. $_{10}^{22}Ne$
5. $_{2}^{4}He$
6. $_{55}^{133}Cs$
7. $_{92}^{234}U$
8. Atomic number: 12, Mass number: 24
9. Atomic number: 12, Mass number: 24