An Introduction to Atoms

As you complete the lesson, you will need to fill in the information on your notes page and use that information to answer questions as you progress through the lesson.

• Atoms are the basic unit that makes up all matter.

  • Remember: Matter is anything that has both mass and volume.

• We can only see atoms if we use a very strong microscope. It is called an electron microscope.

Electron microscope

• The nucleus of an atom is the center.

• The nucleus is made of neutrons and protons.

• Electrons rotate in electron clouds around the nucleus.

  • Protons = positive electrical charge

  • Neutrons = no electrical charge (neutral)

  • Electrons = negative electrical charge

    • Smallest part of an atom.

• Most atoms are neutral. This means the number of protons is equal to the number of electrons.

• Examples:

  • Hydrogen:

    • Number of protons = 1

    • Number of electrons = 1

  • Oxygen

    • Number of protons = 8

    • Number of electrons = 8

​Hydrogen

Oxygen

• Sometimes atoms combine. When two or more atoms combine, they make a molecule.

  • Examples: Water, Sodium Chloride (Table Salt)

• When the atoms that combine are the same, they are called an element.

  • Examples: Gold, Silver, Hydrogen

• If the atoms that combine are different, they're still molecules, but they are called compounds.

  • Examples: Water, Glucose (Sugar)

• Label your atom to reflect the parts of the atom shown below.

Use the diagram to count the number of each particle. Fill out the number of each on your notes page:

• Number of protons = ___

• Number of electrons = ___

• Number of Neutrons = ___

Atoms with 6 protons and 6 electrons are known as Carbon.