Practice Problems: The Atom (Answer Key)

  1. How many electrons, protons and neutrons are there in the following atoms:

    a. 40Ca  20 e-, 20 protons, 20 neutrons

    b. 119Sn  50 e-, 50 protons, 69 neutrons

    c. 244Pu  94 e-, 94 protons, 150 neutrons

  2. What are the mass numbers for the following atoms:

    a. beryllium with 5 neutrons  9

    b. titanium with 26 neutrons  48

    c. gallium with 39 neutrons  70

  3. Give the atomic symbol for each of the following elements using the format .

    a. sodium with 12 neutrons  

    b. argon with 21 neutrons  

    c. lead with 126 neutrons  

  4. How many protons, neutrons and electrons are contained in a neutral ruthenium-101 atom?

    44 protons, 57 neutrons, 44 electrons

  5. Fill in the blanks in the following table (each column in the table represents a different element). Assume each atom is uncharged.


    Symbol

    Number of protons

    21 16 8
    25
    Number of neutrons

    24 17 9
    31
    Number of electrons

    21 16 8 25




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