Ernest Rutherford Lesson for Kids: Facts & Atomic Theory

Instructor: Emily Lockhart

Emily has taught science and has a master's degree in education.

Ernest Rutherford was a scientist whose work helped identify the smallest particles in any object. His experiments laid the foundation to understanding atoms. Let's explore more about Rutherford and his atomic theory.

Who is Ernest Rutherford?

Have you ever heard of atoms? Atoms are the tiny units that make up everything in the universe. Just like the letters in the alphabet can combine to make the vast amount of words in language, atoms are the tiny units that make up everything in the universe you can touch and feel.

In the early 1900s, many scientists believed that the atom was one substance throughout. But scientist Ernest Rutherford thought the atom was made of smaller particles, and he conducted experiments to prove this theory. In fact, because of his contributions to the field, an element on the periodic table has been named Rutherfordium in his honor.

Ernest Rutherford

Rutherford's Atomic Theory

Scientists already had a clear picture that all objects were made of atoms. Rutherford's theory built on that knowledge, claiming that the atom is not one solid substance, but that it's made of different parts--a nucleus with positively charged protons and neutral neutrons surrounded by negatively charged electrons. To see if atoms were one big particle or if they were made of multiple smaller particles, Rutherford experimented with pure gold foil.

He passed what he called alpha particles through the foil (an alpha particle is the same as the nucleus of helium atom). If atoms were one solid particle, they would be packed together like a bag of marbles. The alpha particles, which are smaller, would pass between the atoms and come out the other side. However, if there was an object in the center of the atom, some of the alpha particles would be bounced back. This last scenario is what occurred. The alpha particles were bouncing back because they were hitting the nucleus of the gold atom, proving that an atom is made up of different parts!

The number of protons plus the number of neutrons equals the atomic mass.

It is now known that the nucleus of an atom is made of two different particles--protons and neutrons. The protons carry a positive charge, and the neutrons carry a neutral charge. Adding up the mass of the protons and neutrons gives us the mass of that atom, which is called atomic mass. For example, helium has two protons and two neutrons and, therefore, an atomic mass of four.

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