HMH PS U3L4E2 analyzing the structure of matter

​Some solid elements and compounds are not composed of particles that are single atoms or individual molecules.

• have repeating subunits of atoms, not individual molecules

• Iron

• Extended structures with a repeating structure of atoms

• highly regular structure of atoms define many of a crystal’s properties.

• Diamonds are crystals.

​Crystals

Extended Structures

​Do the Math

Each molecule of a substance is exactly the same. The atoms that make up the substance always combine in a fixed ratio. A ratio tells how much of one thing there is compared to another. When describing molecules, a ratio tells how much of one element there is compared to another element in the same molecule. For example, a molecule of water has 2 hydrogen atoms for every 1 oxygen atom. In other words, its ratio of hydrogen atoms to oxygen atoms is 2 to 1. Other ways to write the ratio are 2:1 and ​​ 2/1 ​​.

how would you write the ratio for each of these substances.

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ratios

​Models

• models show how molecules are joined together

• held together by a chemical bond- an attractive force, not really visible

• can show bond as stick, or just show molecules together
  

​Models of extended structures

A model of an extended structure needs to show how the atoms are attached to one another

Need to show the structures and repeating subunits that the atoms form, ball and stick models are often used.

​Modeling complex molecules

• A simple molecule may contain a few atoms bonded together. A complex molecule may contain thousands of atoms.

• The atoms in complex molecules often form repeating patterns. A repeating unit can be formed by a single type of atom or two or more different types of atoms.

• Most of the molecules of life are made up of complex molecules based around carbon. Complex molecules like these are possible because carbon atoms are able to form very stable bonds with each other.

This model shows how a molecule of the plastic polyvinyl chloride (PVC) is made up of repeating units of carbon, hydrogen, and chlorine atoms.

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