02-04 Atomic Structure Questions
Name: ____________________________
1. The extremely low-mass, negatively charged particle found outside the nucleus is
called an electron.
2. The number of protons in the nucleus of the atom is indicated by the atomic
number.
3. The symbol for an element is either a capital letter or possibly a capital letter
followed by a lower case letter.
4. Atoms of the same element that differ in their number of neutrons in the nucleus
are called isotopes.
5. The total number of nucleons (particles in the nucleus) in the atom make up the
mass number.
6. A neutral nuclear particle having a mass of about 1 AMU is called the neutron.
7. The proton is a positively charged nuclear particle with a mass of about 1 AMU.
8. The nucleus is the small, positively charged center of the atom.
9. In a neutral atom, the number of protons in the nucleus equals the number of
electrons outside the nucleus.
10. An element’s atomic number is different from that of any other element.
11. The atomic number identifies the specific element.
12. The neutron and the proton have nearly the same mass, which is about 1840 times
more massive than the electron.
13. More than 99% of the mass of the atom is concentrated in the nucleus.
14. The AMU or atomic mass unit is the basic unit of atomic mass and it is equal to
1/12 the mass of the carbon-12 atom.
15. The total number of protons and neutrons in an atom is called the mass number.
16. Isotopes are atoms that have the same number of protons, but different numbers
of neutrons.
17. U-234 and U-238 represent isotopes of the same element.
18. Na-24 and Mg-24 represent isotopes of two different elements.
19. The charge of one proton balances the charge of one electron.
20. The protons and neutrons present in the nucleus are collectively called nucleons.
(Hint – see number 5 above.)
21. Atoms that have the same number of protons, but a different number of neutrons
are called isotopes.
22. Two nuclei with the same number of protons, but different mass numbers are
referred to as isotopes.
23. Uranium is known to have 143 neutrons. What is its mass number? 235
24. An isotope of this element (Uranium) has 146 neutrons. What is that isotope’s mass
number? 238
25. Which of these has the largest number of neutrons per atom?
02-04 Atomic Structure Questions
Name: ____________________________
a. Bi-210 (210 – 83 = 127 neutrons) – this as the most!
b. Po-210 (210 – 84 = 126 neutrons)
c. At-210 (210 – 85 = 125 neutrons)
d. At-211 (211 – 85 = 126 neutrons)
26. Identify whether each of these pairs is an isotope of each other or not:
a. Lu-154 and Lu-161 (Yes)
b. Yb-167 and Lu-167 (No – these are isotopes of different elements)
c. Two atoms, both with atomic number = 84 and mass number = 204 (No –
these are the same isotope of the same element!)
d. Two atoms, one with atomic number = 53 and mass number = 133; the other
with atomic number = 53 and mass number = 137 (Yes – these happen to be
isotopes of Iodine)