1. Atoms and Atomic Structure
Unit 2 Review
Atoms and Atomic Structure

2. 1. The letter “X” in the diagram above marks the:
Location of the neutrons
Region of greatest density
Electron cloud
Location of the protons

3. 2. The region labeled "Y" in the diagram has a charge that is:
Positive
Negative
Neutral
None of the above

4. The number of protons in the nucleus The number of electrons
3. Isotopes (such as hydrogen-1, hydrogen-2, and hydrogen-3) are atoms of the same element that differ in:
The number of protons in the nucleus
The number of electrons
The atomic number
The number of neutrons in the nucleus

5. 4. The atomic number of an element is equal to:
A. the number of protons in the nucleus B. the number of protons plus the number of electrons C. the number of protons plus the number of neutrons D. the number of neutrons in the atom

6. 5. The charge and mass number of an electron are:
A. charge = 0, Mass number = 1
B.   charge = +1, Mass number = 0
charge = +1, Mass number = 1
charge = -1, Mass number = 0

7. 6. A fictitious element X is composed of 10
6. A fictitious element X is composed of 10.0 percent of the isotope X-55 , 20.0 percent of the isotope X-56 , and 70.0 percent of the isotope X-57 . Estimate the atomic mass of element X.
A. 57 amu B. 57 C amu D. 56.6

8. 7. Which of the following is true about subatomic particles?
Electrons are negatively charged and are the heaviest subatomic particle.
Protons are positively charged and the lightest subatomic particle.
Neutrons have no charge and are the lightest subatomic particle.
The mass of the neutron nearly equals the mass of a proton.

9. 8. The mass number of an atom is determined by:
A. the number of protons only
B.   adding the neutrons and electrons
C.  adding the neutrons and protons
D.  adding the protons and electrons

10. 9. The nucleus of most atoms is made up of:
A. electrons and protons
B.  protons and electrons
C.  neutrons and electrons
D.  protons and neutrons

11. 10. In which of the following sets is the symbol of the element, number of protons, and the number of electrons given correctly?
In, 49 protons, 49 electrons
Zn, 30 protons, 60 electrons
Cs, 55 protons, electrons
F, 19 protons, 19 electrons

12. 11. Which of the following is correct concerning subatomic particles?
The electron was discovered by Goldstein in 1886.
The neutron was discovered by Chadwick in 1932.
The proton was discovered by Thomson in 1880.
Cathode rays were found to be made of protons.

13. A. Uranium-238 has a larger electron cloud than uranium-235
12. An atom of uranium-238 differs from an atom of uranium-235 in the following way:
A. Uranium-238 has a larger electron cloud than uranium-235
B.   Uranium-238 has three more neutrons than uranium-235
C.  Uranium-238 has three more protons than uranium-235
D.  Uranium-238 has three more electrons than uranium-235

14. 13. Which of the following is NOT a part of Dalton’s atomic theory?
All elements are composed of atoms.
Atoms are always in motion.
Atoms of the same element are identical.
Atoms that combine do son in simple whole-number ratios.

15. 14. Which of the following statements is NOT true?
Atoms of the same element can have different masses.
Atoms of isotopes of an element have different numbers of protons.
The nucleus of an atom has a positive charge.
Atoms are mostly empty space.

16. 15. Which of the following accurately summarizes the isotope Argon-40?
A. 18 protons, 18 electrons, 22 neutrons B protons, electrons, neutrons C. 22 protons, 22 electrons, 18 neutrons D. 40 protons, 40 electrons, 18 neutrons

17. 16. Which of the following was NOT among Democritus’ ideas?
Matter consists of tiny particles called atoms.
Atoms are indivisible.
Atoms retain their identity in a chemical reaction.
Atoms are indestructible.

18. 17. As a consequence of the discovery of the nucleus by Rutherford, which model of the atom is thought to be true?
Protons, electrons, and neutrons are evenly distributed throughout the volume of the atom.
The nucleus is made of protons, electrons, and neutrons.
Electrons are distributed around the nucleus and occupy almost all the volume of the atom.
The nucleus is made up of electrons and protons.

19. Answers
1. C 6. C 11. B 16. C
2. A 7. D 12. B 17. C
3. D 8. C 13. B
A 9. D 14. B
D 10. A 15. A