Atoms are the smallest particle of an element that retains the characteristics of the element. Yea! I know that this is not the easiest thing to explain. So, let’s start with the element carbon.

The diagram represents one carbon atom.

The Circle:

The circle represents the nucleus, which contains 6 protons (positive charges).  Only carbon atoms have  six protons. I repeat:  No other atom has six protons.

Atomic Number: This is the number of protons that an atom has. Every known element has its own  atomic number. Again: No two atoms have the same atomic number.

Carbon’s atomic number is 6.

Outside the Circle:

Electron: Negatively charged particles moving outside the nucleus of an atom.
Carbon: Each carbon atom has six electrons moving outside its nucleus.
An atom has an equal number of protons and electrons.

All carbon atoms have the same number of protons and electrons. But all carbon atoms are not exactly alike.

Isotopes: Atoms of the same element that have different mass numbers.

Mass Number: This is the sum of the protons and neutrons in the nucleus of an atom.

Neutron: A particle found inside the nucleus of an atom. This particle does not have a charge.

Carbon -12: The most common natural isotope of the carbon element. The mass number of this isotope is given after its name. The diagram for C-12 contains the protons and neutrons found in the nucleus of this carbon isotope.

Challenge:

1. What is the name of the carbon isotope shown in the diagram to the left?

Answer:

Think!

1. You know it is a carbon isotope because it has 6 protons.

2. The mass number of any atom is equal to the number of protons plus the number of neutrons in the atom’s nucleus.

3. The mass number for the diagram is:  6 protons + 7 neutrons = 13

4. The name of a specific isotope of an element is the:

elements name + mass number (carb0n-13)
symbol of the element + mass number (C-13)

On Your Own

The only other naturally forming carbon isotope is C-14.

1. How many protons does one atom of C-14 have? (6)

2. How many neutrons does one atom of C-14 have? (7)

3. How many electrons does one atom of C-14 have? (6)

4. What is the atomic number for C-14? (6)

5. What is the mass number for C-14? (13)

For more information about this element, see   CARBON.

For advanced learners, See How C-14 is Used for Dating Fossils.