WEIGHING & COUNTING ATOMS

Multiple Choice

1. The atomic number of oxygen, 8, indicates that there are eight
            (A) protons in the nucleus of an oxygen atom
            (B) oxygen nuclides
            (C) neutrons
outside the oxygen atom's nucleus
            (D) energy levels moving around each oxygen nucleus

2. The number that is the total number of protons and neutrons in the nucleus of an atom is the
            (A) atomic number                (B) Avogadro number           
            (C) mass number                  (D) number of neutrons

3. Isotopes of a particular element differ in
            (A) the number of neutrons in the nucleus
            (B) atomic number
            (C) the number of electrons in their outermost energy level
            (D) the total number of electrons

4. In determining atomic mass units, the standard is a(n)
            (A) C - 12 atom            (B) C - 14 atom           
            (C) H - 1 atom              (D) O - 16 atom

5. The chemical shorthand for atomic mass units is
            (A) amu            (B) mu            (C) a            (D) am

6. The average atomic mass of an element is the weighted average of the atomic masses of the
            (A) naturally-occurring isotopes            (B) two most abundant isotopes
            (C) nonradioactive isotopes                  (D) artificial isotopes

7. The number of atoms in one mole of carbon is
            (A) 6.022 x 1022                    (B) 6.022 x 1023           
            (C) 5.022 x 1022                    (D) 5.022 x 1023

8. The number of atoms in a mole of any substance is called
            (A) the atomic number            (B) Avogadro's number
            (C) the mass number              (D) the molar mass

9. As the atomic masses of the elements in the Periodic Table increase, the number of atoms in one
    mole of each element
            (A) decreases            (B) increases            (C) remains the same
            (D) becomes a negative number

Problems

10. Oxygen has two isotopes: O-16 and O-18.  Naturally-occurring oxygen consists of 99.759% of
      oxygen 16.  What is the average atomic mass of oxygen according to these numbers?

11. How many neutrons does Zn-66 (atomic number 30) have?

12. Ag-109 has 62 neutrons.  How many electrons does the neutral atom have?

13. An atom of chlorine has an atomic number of 17 and a mass number of 35.  How many protons,
      neutrons, and electrons does it have?

14. Neon has 3 natural isotopes: Ne-20 (90.51%), Ne-21 (0.27%), and Ne-22 (9.22%).  What is neon's
     average atomic mass?

15. What is the mass of two moles of oxygen atoms if the average atomic mass of oxygen is 16 amu?

 

Back to the Unit 3 Worksheets Page

Back to the Unit 3 Page

Back to the Main Page