Unit 6—Properties of Matter

Chapter 18: Atoms and Elements

Lab 18.2—Comparing Atoms

In this investigation, you will investigate the structure of the atom and identify what makes atoms of different elements different from each other.

We once believed that atoms were the smallest unit of matter. Then it was discovered that there are even smaller particles inside atoms (J.J. Thomson). The structure of the atom explains why nearly all the properties of matter we experience are what they are. This investigation will lead you through some challenging and fun games that illustrate how atoms are built from protons, neutrons, and electrons.

In this investigation, you will use the atom board game to learn about atomic structure. The marbles will represent the three particles in the atom. Red marbles are protons, blue marbles on neutrons, and yellow marbles are electrons. The position of the marbles on the board shows where the real particles are in the atom. The neutrons and protons are in the nucleus (center) and the electrons are arranged in energy levels around the outside.

Procedure/Data/Results:

  1. Using the atom game board and the correctly colored marbles, build an atom of lithium-6.
  2. Using the mass number periodic table provided, answer each of the following:
  1. What is the number below the element symbol? What does this number tell you about the atom?
  1. What is(are) the number(s) above the element symbol called? What does this tell you about the atom?
  1. Why do some elements have more than one number above the symbol? What are the variations in this number called?
  1. Build the six atoms shown in the chart on the next page and fill in the missing information. Protons and neutrons go in the middle of the board. Electrons go in the outside and fill up the holes from the lowest row (closest to nucleus) to the highest (furthest from the nucleus).

Element / Atomic Number / Mass Number / Protons / Neutrons / Electrons
3a. / 4 / 5
3b. / 6 / 6
3c. / 7 / 6
3d. / 8 / 8
3e. / 10 / 10 / 10
3f. / 27 / 13
  1. Two of the atoms you made were the same element. What was different about them?
  1. One of the atoms had just enough electrons to completely fill the first two rows. Which atom was this? Where on the periodic table is it found?
  1. What atom had an atomic number of 8?
  1. Which atom had a mass number of 13?
  1. One atom is found in a lightweight, silvery metal used in airplanes. Which atom is it?
  1. One atom represents an element that makes up about 21% of the Earth’s atmosphere. Which atom is it?
  1. Playing the game of atomic Challenge. Each player takes a turn adding protons, neutrons, and electrons to the atom to build heavier and heavier elements. The winner is the first player to run completely out of marbles. Play a few games until everyone in your group is proficient.
  2. Each player should start with 6 blue (neutrons), 5 red (protons), and 5 yellow (electrons) marbles.
  3. Each player takes a turn add 1-5 marbles, but not more than 5. The marbles may include any mixture of electrons, protons, and neutrons. For example, you can add one blue, one red, and one yellow marble in a turn. That makes 3 total marbles which is less than 5.
  4. Marbles played in a turn are added to the marbles already in the atom.
  5. Only atoms where the electrons, protons, and neutrons match one of the naturally occurring elements on the mass number periodic table are allowed. If you add marbles that make an atom NOT on the periodic table you have to take your marbles back and try again.

The Three Rules: Rule #1—The number of protons matches the atomic number.

Rule #2—The total number of protons and neutrons equals a stable

mass number.

Rule #3—The number of electrons matches the number of protons.

  1. A player can trade marbles with the bank INSTEAD of taking a turn. The player can take as many marbles, and of as many colors as they need but must take at least as many total marbles as they put in. For example, a player can trade 2 yellows for 1 yellow, 1 blue, and 1 red.
  1. Which particles are found in an atom’s nucleus? Which particles are found outside the nucleus?
  2. What four elements make up almost all of the mass in your body?
  3. What is the atomic number of sodium?
  4. How many protons does sodium have?
  5. How many stable isotopes does oxygen have?
  6. Name one element that is always radioactive and has an atomic number less than 50.
  7. Find and list here the name and symbol of three additional elements that have no stable isotopes.
  1. What element has 26 protons in its nucleus?
  2. How many different isotopes does magnesium have?
  3. How many protons, neutrons, and electrons does Mg26 have?
  4. If an isotope of silicon has 15 neutrons, what is its mass number?
  5. What is the heaviest element with at least one isotope that is NOT radioactive?
  6. On most periodic tables, a single atomic mass is listed instead of the mass numbers for all the stable isotopes. How is this mass related to the different isotopes?