THE ATOM

Chapter 6 – 2Part 2

ISOTOPES• Isotopes are atoms

that have the same number of protons, but have different numbers of neutrons.

• Having a different number of neutrons gives the atom a different mass.

• Isotopes of the same element are similar to one another in many ways.

• Some elements have isotopes whose properties differ in important ways.

PROPERTIES OF ISOTOPES• Some isotopes of an element have

special properties because they are unstable.

• This type has a nucleus that will change over time.

• These are radioactive because they will fall apart over time.

• Most isotopes share most of the same properties.

The Difference Between Isotopes• You can identify an isotope by its mass number.• The mass number is the number of protons and

neutrons added together.• Compare these three carbon atoms to see how

we determine the mass number for each.

NAMING ISOTOPES• To identify a specific isotope of an

element, write the name of the element followed by a hyphen and the mass number.

• Example: Hydrogen – 2

Hydrogen - 3

Isotopes and Atomic Mass• Most elements contain a

mixture of two or more isotopes with different #’s of neutrons.

• The atomic mass of an element is the average of the masses of all the naturally occurring isotopes of that element.

• This number is found on the element card on the periodic table.

6

C12.01

ATOMIC MASS

Forces in Atoms• There are four basic forces acting

between the particles in an atom that hold them together.

• These forces work together to give an atom its structure and properties.

Gravitational Force• Gravitational force pulls objects towards

one another.

• The masses of the particles in atoms are so small, this force within atoms is very small.

Electromagnetic Force• Protons and electrons are attracted to

each other because of this force.

STRONG FORCE• Protons push

away from each other because they have the same charge.

• The protons would fly apart if it wasn’t for strong force.

WEAK FORCE• The weak force is an important force

in radioactive atoms.• In certain atoms, a neutron can

change into a proton and an electron.

• The weak force plays a big part in this change. +

-NEUTRAL

IONS

• An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons,

LET’S TRY IT!

TIME FOR THE

“MADE TO ORDER”

LAB