Materials Included In Kit

Additional Materials Required

Prelab Preparation

1. Create 18 bags containing marbles.
2. With a marker, label the bags A through R.
3. Using the student data table as a template or using your own examples, add the correct number of protons (black marbles) and neutrons (blue marbles) to each bag.
4. With a marker, write the number of electrons on each bag.

Lab Hints

• For 18 atom samples, there are an average of about 16 protons (black marbles) and 16 neutrons (blue marbles). All materials are reusable. This allows the inclusion of some row four elements as samples. The number of lab samples can be reduced to include the higher atomic number elements.
• A list of isotopic composition of the elements is useful in creating various isotopes for the lab stations.
• This activity kit is complemented by Introduction to Electron Structure, Catalog No. AP6602, which looks at the electron energy levels, and is available from Flinn Scientific, Inc.
• Large weighing dishes can be used in addition to the ZipLoc bags.
• The activity can be updated to include orbitals s, p, d and f for the electrons. Mark the corner of the bags with the orbital and number of electrons (i.e., 1s²2p⁶).
• The American Chemical Society dictates that ions be written with the number first, followed by the charge. Therefore Fe³⁺ is correct, Fe⁺³ is incorrect.
• The “nuclei” can be stored in their bags to be used for later classes.

Answers to Prelab Questions

1. What is the element name for the following atoms.
   1. 6 protons, 6 neutrons and 6 electrons. Carbon
   2. 18 protons, 20 neutrons and 18 electrons. Argon
   3. 3 protons, 4 neutrons and 3 electrons. Lithium
2. Write the isotope name for the following atoms.
   1. 8 protons, 8 neutrons and 8 electrons. Oxygen–16
   2. 15 protons, 16 neutrons and 15 electrons. Phosphorus–31
   3. 30 protons, 36 neutrons and 30 electrons. Zinc–66
3. An atom has 23 protons, 27 neutrons and 23 electrons; a second atom has 23 protons, 28 neutrons and 23 electrons; and a third atom has 23 protons, 27 neutrons and 18 electrons.
   1. What is the name and symbol of the element? Vanadium, V
   2. What is the atomic mass number of each atom? 50, 51, 50
   3. What is charge on each atom? zero, zero, 5+
   4. Write the ion. V⁵⁺
4. Write the ions for the following atoms.
   1. 5 protons, 6 neutrons and 2 electrons. B³⁺
   2. 37 protons, 48 neutrons and 36 electrons. Rb⁺
   3. 16 protons, 16 neutrons and 18 electrons. S^2–

Sample Data

Teacher Handouts

13888_Teacher1.pdf

References

Special thanks to Lee Marek, retired chemistry teacher, Naperville High School, Naperville, IL, for providing the procedure for this activity to Flinn Scientific.

Introduction

Use this simple and straightforward activity to help students understand the basics of a fundamental atomic concept, the nucleus and its particles.

Concepts

• Atom
• Atomic number
• Isotope
• Ion

Background

Matter is defined as any substance that has mass and occupies a volume. All matter is either a pure element or a combination of elements. Elements are matter that cannot be separated by chemical or physical means. Each element has its own unique properties, such as melting point, density, and the way it reacts chemically. There are 90 elements that are naturally occurring. The smallest part of an element that still has these same properties is call an atom. All atoms are made up of three types of particles; protons, neutrons, and electrons. The number of protons in an atom is called its atomic number. Every atom of each element has exactly this number of protons.

Two of these three particles possess electrical charge. The proton has a positive (+) charge, the electron has a negative (–) charge, and the neutron has no electrical charge. An atom always has equal numbers of the positively charged protons and the negatively charged electrons, giving the atom zero electrical charge.

The electrons are very mobile and can range from the center of the atom to its outer edge. The best model that represents the electrons and their movement is the electron cloud model (see Figure 1). Protons and neutrons are always together in the center, or nucleus, of the atom (see Figure 1). The size of the nucleus is very small and very compact when compared to the size of the atom itself. In fact, as a comparison if the nucleus were the size of a golf ball, the atom’s outer edge would be 2¾ miles away! A model of an atom is shown in Figure 1.

Though electrons have the same, but opposite, charge as that of protons, their mass is extremely small compared to the protons and neutrons, which are approximately of equal mass. The mass of the atom is therefore determined by adding together the masses of the protons and neutrons. The total number of protons and neutrons in an atom is called its atomic mass number.

When two atoms have the same number of protons, but different numbers of neutrons, they are called isotopes. Since isotopes have the same number of protons, they are the same element and are identical in the ways they react. For example, atoms with 17 protons are called chlorine atoms. There are two isotopes of chlorine. One isotope has 17 protons and 18 neutrons. Its atomic number is 17 (chlorine) and its atomic mass number is 35. The isotope is written as the element name, followed by the atomic mass number. This isotope of chlorine is written chlorine–35. The other isotope of chlorine has 17 protons and 20 neutrons and is written chlorine-37.

All the elements are arranged in a chart called the periodic table. The elements are listed in order of increasing atomic number, from left to right and top to bottom. Each element is enclosed in a box in the periodic table. The box typically contains the element name, its one- or two-letter symbol and its atomic number (see Figure 2). To determine the element name of an atom, count the number of protons and look for this atomic number on the periodic table.

In chemical reactions, atoms tend to gain or lose their electrons. If an atom loses or gains electrons and now has an unequal number of protons and electrons, it is called an ion. If an atom contains 17 protons, 18 neutrons, and 18 electrons, then the atom is a chloride ion. Ions are written using the element symbol, with the net number of electrons gained or lost at the top and right of the symbol. If the ion has lost electrons, a + sign is put after the number; if the ion has gained electrons, a – sign is used. If the ion has lost or gained only one electron, the number 1 is omitted from the ion symbol. The chloride ion, with one extra electron, is written Cl^–.

If an atom has 20 protons and 18 electrons and the atom has lost two electrons, then the ion is a calcium atom (atomic number 20) and the electrical charge is 2+ (20 – 18 = 2). The ion is written as Ca²⁺.

Materials

Prelab Questions

1. What is the element name for the following atoms.
   1. 6 protons, 6 neutrons and 6 electrons.
   2. 18 protons, 20 neutrons and 18 electrons.
   3. 3 protons, 4 neutrons and 3 electrons.
2. Write the isotope name for the following atoms.
   1. 8 protons, 8 neutrons and 8 electrons.
   2. 15 protons, 16 neutrons and 15 electrons.
   3. 30 protons, 36 neutrons and 30 electrons.
3. An atom has 23 protons, 27 neutrons and 23 electrons; a second atom has 23 protons, 28 neutrons and 23 electrons, and a third atom has 23 protons, 27 neutrons and 18 electrons.
   1. What is the name and symbol of the element?
   2. What is the atomic mass number of each atom?
   3. What is charge on each atom?
   4. Write the ion.
4. Write the ions for the following atoms.
   1. 5 protons, 6 neutrons and 2 electrons.
   2. 37 protons, 48 neutrons and 36 electrons.
   3. 16 protons, 16 neutrons and 18 electrons.

Safety Precautions

The materials used in this activity are considered nonhazardous. Follow all standard laboratory safety practices.

Procedure

1. At the lab benches are 18 bags labeled A–R. Each bag contains various amounts of black and blue marbles, with a number written on the outside of the bag. The black marbles represent protons, the blue marbles neutrons, and the written number represents the total number of electrons.
2. For each bag, record the number of protons, neutrons and electrons in the data table.
3. Using these values and the periodic chart, deduce the information needed to complete the data table for each bag. If the atom is an ion, write its symbol in the “Ion Symbol” column.

Student Worksheet PDF

13888_Student1.pdf