You Are Going to Learn About a Model That Scientists Use to Describe What Is Inside the Atom

You are going to learn about a model that scientists use to describe what is inside the atom.

Atoms have a central part called the nucleus. The nucleus contains the protons. Whizzing around the nucleus are the electrons.

The electrons are grouped together. The group closest to the nucleus is said to make up the 'inner shell', and the second closest group makes up the 'second shell'. An atom can have up to seven 'shells'.

The sodium atom in the diagram has three shells, represented by the three circles around the central nucleus.

How many protons are in the sodium atom?

How many electrons are in the sodium atom?

How many electrons are in:

athe inner shell

bthe next shell

cthe outer shell?

Where else have you heard the word 'nucleus'?

What is similar about the atom's nucleus and the other nucleus?

The shells are filled up in order from the inside. The inner shell can take two electrons and the second shell takes eight electrons. Sodium has one more electron, which is in the outer shell.

You may remember electrons from when you studied electricity. Electrons move along the wires, carrying the energy. If you made a wire out of sodium (difficult and dangerous, but not impossible) it would be the electron from the outer shell that moved between atoms, carrying the energy.

Protons and electrons are charged and charge comes in both negative and positive amounts. Electrons have a charge of –1 each. Protons have a charge of +1 each.

Add up all the charges in the sodium atom.

Atoms in an element contain the same number of protons as electrons. This means that the overall charge of an atom in an element is zero.

The number of protons in an atom is called the atomic number.

For the atoms in an element, the atomic number also gives the number of electrons, because the number of protons equals the number of electrons.

Carbon has atomic number 6.

aHow many protons does it have?

bHow many electrons does it have?

cLook at the diagram for the sodium atom. Draw a similar diagram for a carbon atom.

This worksheet may have been altered from the original on the CD-ROM.