Structures, Models, Molecules

Atoms and elements can be represented in several ways, including ball and stick models and chemical formula.
Different representations are useful for different situations.
Understand the meaning of valency.
MS-ETS1-2. Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.

Guiding Ideas

Lesson 5

Chemical formula provide information about how many atoms of a particular element are in a molecule. Structures provide information about how the atoms are arranged in space and how they bond to each other.

Atoms are commonly represented by balls of different colors. By convention the colors schemes used are:

Hydrogen - White

Carbon - Black

Oxygen - Red

Sulfur - Yellow

Nitrogen - Blue

Phosphorus - purple

Halogens (chlorine, bromine, iodine, fluorine) - green

Metals - Grey

Three dimensional molecular models are built by connecting these balls together with sticks that represent chemical bonds. Two dimensional models are drawn using the elements' chemical symbol and connecting the atoms with lines.

Elements can form different number of bonds, this is known as valency. For example, carbon can form 4 bonds so we say it has a valency of four. Hydrogen has a valency of one, so it can only form 1 bond. This means that 1 carbon can form bonds with 4 hydrogen atoms, to create CH4. Oxygen has a valency of two, nitrogen (normally) has a valency of 3.

Students may discover that a chemical formula does not always provide enough information to be able to build a molecular structure. There are 2 ways that C4H10 can be constructed. These 2 molecules are known as isomers. Isomers are molecules that have the same formula but different structures.

Student Activities

Students should create simple structures to represent atoms of a particular element using, for example, colored wool.

First create molecular models of compounds containing just carbon and hydrogen (hydrocarbons). Then increase the complexity of the molecule by introducing oxygen and nitrogen.

Alternatively students can create two dimensional representations of molecules using the element blocks available in Minecraft.

For guidance students can look for compounds in Minecraft that contain carbon, hydrogen, oxygen and/or nitrogen and then try and build structures of these molecules.