CHEM310 Laboratory Exercise #3 - Atomic Structure

Chemistry 310

Laboratory Exercise #3 Atomic Structure

Introduction: The theory of Democritus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms, there lies empty space; that atoms are indestructible, and have always been and always will be in motion; that there is an infinite number of atoms and of kinds of atoms, which differ in shape and size.

In 1897, while working with a Crookes discharge tube, J. J. Thomson determined the charge-to-mass ratio of cathode rays and was given credit for the discovery of the electron.

In 1906, Ernest Rutherford (a former student of J. J. Thomson) and his student, Hans Geiger, fired alpha particles at thin gold foils. If the plum pudding model of the atom was correct, α particles should pass through undeflected.

Based on the massiveness of the nucleus, Rutherford predicted that it must contain neutral particles in addition to positively charged protons. Neutrons, n0, were discovered by James Chadwick in 1932.

Rutherford had discovered the atomic nucleus and proposed a new model of the atom.

Within subatomic particles, nucleus consisted of protons that carry a single positive charge. Number of proton is called atomic number. Nucleus also contains neutrons that have no charge and can vary from atom to atom. Outside the nucleus, there are electrons that carry negative charge and responsible for most of the chemistry that happens.

Objective: The objective of this laboratory exercise is to introduce the theory of atomic structure.

Experimental procedure:

Step 1: Open and access the link by holding Ctrl and clicking on this link https://phet.colorado.edu/en/simulation/build-an-atom

You should see this screen once you’ve successfully opened the link.

Play button

Step 2: Press on the play button to open the app. You should see the screen below.

Step 3: Click on the first tile, the one that says “Atom” to access the “Build an Atom” screen.

Step 4: This exercise is designed to help you get familiar with the atoms in the Period table. You can start building atoms by adding protons, neutrons and electrons.

For example, if you added one proton and one electron, a neutral hydrogen atom was built.

Step 5: Click on the second tile, the one that said “Symbol” to access the symbol tab.

Step 6: Using the Atom tile and Symbol tile, answer questions in the report sheet.

Step 7: you can have fun with educational games while doing chemistry lab in the Game tile.

Using the Atom and Symbol tiles, answer the following questions.

Write the atomic symbol for each of the isotopes described below.

a. The isotopes of Carbon with 7 neutrons

b. The isotopes of Carbon with 6 neutrons

c. Number of neutrons = 8, Z= 6

d. Atomic number is 5, mass number is 11

e. Number of protons = 5, number of neutrons = 5

f. Isotope of boron with mass number 10

g. Z = 26, A= 54

h. The isotope of iron with 30 neutrons

i. Number of protons = 26, number of neutrons = 31

j. The isotope of nitrogen with 7 neutrons

k. Z = 7, A = 15

f. atomic number = 7, number of neutrons = 8

2. What did you learn from this experiment?