Name: Period: Score:

The Dotting Game

You have learned that atoms are composed of protons, neutrons and electrons. The electrons occupy energy levels that surround the nucleus in the form of an “electron cloud”. The electrons that are involved in forming chemical bonds are called valence electrons. Atoms can have up to eight valence electrons. These electrons exist in the outermost region of the electron cloud often called the “valence shell”.

Valence Clues

The diagram below represents various atoms in which only the valence electrons are shown. Use the diagrams to provide the missing information.

Element / Number of Valence Electrons / Metal, Non-Metal, Metalloid / Group Number / Period Number

The most stable atoms have eight valence electrons. When an atom has eight valence electrons, it is said to have a complete octet. Atoms will gain or lose electrons in order to complete their octet. In the process of gaining or losing electrons, atoms will form chemical bonds with other atoms. The method we use to visually represent an atoms valence state is called a “dot diagram”, and you will practice drawing these in the following exercise.

What is a dot diagram?

Dot diagrams are composed of two parts- the chemical symbol for the element and dots surrounding the chemical symbol. Each dot represents one valence electron. If an element such as oxygen, has six valence electrons, then six dots will surround the chemical symbol as shown to the right.

Boron has three valence electrons, so three dots surround the chemical symbol for boron as shown to the right.

There can be up to eight dots around a symbol, depending on the number of valence electrons the atoms has. The first four dots are single, and then as more dots are added, they fill in as pairs.

Drawing Dot Diagrams

Using a periodic table, complete the following chart. With this information, draw a dot diagram for each element in the chart. Remember, only the valence electrons are represented in the diagram, not the total number of electrons.

You can get a good idea of how atoms combine with each other just by drawing their valence electrons. In an electron dot diagram, an atom’s valence electrons are shown by dots. Here are the electron dot diagrams for several elements.

HydrogenCalciumSulfur

ChlorineOxygenCarbon

Element / Chemical Symbol / Total Number of Electrons / Number of Valence Electrons / Dot Diagram
Potassium
Nitrogen
Carbon
Beryllium
Neon
Sulfur

Some of these elements combine with each other to form compounds. For example, 1 carbon atom, 3 hydrogen’s and 1 chlorine combine to make methyl chloride. The electron dot diagram for methyl chloride, CH3Cl is shown below.

In each box below, draw an electron dot diagram of the compound described. Also write the chemical formula for each compound. Remember the octet rule (atoms will bond to get 8 electrons in the outer most energy level). Hydrogen and Helium are the exceptions with only two electrons filling their energy level.

1 Hydrogen &
1 Chlorine / 1 Carbon & 4 Chlorine / 1 Carbon & 4 Hydrogen’s
1 Magnesium & 1 Oxygen / 1 Carbon & 2 Oxygen’s / 1 Barium & 2 Chlorines
2 Hydrogen’s & 1 Sulfur / 1 Potassium & 1 Iodine / 1 Magnesium & 2 Bromine

To determine how many atoms of an electron are required for a compound, an electron dot diagram can be used. Atoms of an element need to be added until all the atoms of each element have a full valence shell. An example is listed below.

Draw a dot diagram to identify how many atoms of each element are needed.

Calcium and Chlorine:

Calcium has 2 electrons in its valence shell and Chlorine has 7 electrons in its valence shell. In order to form a compound all atoms in the compound must have a full outer shell. Therefore, you must continue to add atoms of the elements until you have a complete compound. In the above example, Calcium had two electrons to give away, but Chlorine only had one available space to take an electron. To accommodate the needed two slots for the Calcium electrons, two atoms of Chlorine needed to be provided. This way each atom of chlorine could take an electron from Calcium.

The above example shows Ionic Bonding. Ionic bonding is where electrons are exchanged. One element will give up electrons and another element will take them. But, you can also form a compound by sharing electrons. This is a covalent bond. Below is an example of covalent bonding:

Sulfur and Bromine:

Each member of your group has been provided an element on a piece of paper. Find another member of your group and pair together. Build a compound using your two elements. Identify how many atoms of each element would be needed to make a stable compound (each atom having 8 electrons). Record your work in the attached table. Once completed, find a different partner with a different element. Repeat this process three times. Fill in your table as described below.

Name of Partner / Elements / Dot Diagram
Record the name of the person you are working with… / Record the two types of elements you are working with… / Draw the dot diagram that will result in stable compound….

1Georges 11/16/18