Login
Copyright

Atomic Nucleus: Definition, Structure & Size

An error occurred trying to load this video.

Try refreshing the page, or contact customer support.

Coming up next: Background Radiation: Definition, Causes & Examples

You're on a roll. Keep up the good work!

Take Quiz Watch Next Lesson
 Replay
Your next lesson will play in 10 seconds
  • 0:02 The Nucelus
  • 1:05 Atomic Numbers
  • 4:24 Lesson Summary
Add to Add to Add to

Want to watch this again later?

Log in or sign up to add this lesson to a Custom Course.

Login or Sign up

Timeline
Autoplay
Autoplay
Create an account to start this course today
Try it free for 5 days!
Create An Account

Recommended Lessons and Courses for You

Lesson Transcript
Instructor: Kelly Robson

Kelly has taught High School Science and Applied Communications. She holds an Education Specialist Degree in Ed. Leadership.

The atomic nucleus is the central part of the atom. There is a lot to be told by the structure of the atomic nucleus. This lesson goes through he structure of the atomic nucleus and other factors that the atomic nucleus tells us.

The Nucleus

The atomic nucleus is the central area of the atom. It is composed of two kinds of subatomic particles: protons and neutrons.

Diagram showing the atomic structure with the protons and neutrons held together to form the dense area of the nucleus
Atomic Structure

Atoms are the building blocks of all matter. Everything you can see, feel and touch is all made of atoms. There are even things you cannot see, feel, hear or touch that are also made of atoms. Basically, everything is made up of atoms.

In 1909, Ernest Rutherford led Hans Geiger and Ernest Marsden through what is known as the Gold Foil Experiments. During the experiments they would shoot particles through extremely thin sheets of gold foil. In 1911, Rutherford came to the conclusion that the atom had a dense nucleus because most of the particles shot straight through, but some of the particles were deflected due to the dense nucleus of the gold atoms. This theory would eliminate the idea that the atom was structured more like plum pudding. The plum pudding model was the leading model of atomic structure until Rutherford's findings.

Atomic Numbers

The atomic nucleus is in the center of the atom. The number of protons and neutrons in the atom define what type of atom or element it is. An element is a bunch of atoms that all have the same type of atomic structure. For instance, hydrogen is an element. Every hydrogen atom is made up of 1 proton, 0 neutrons, and 1 electron.

The composition of the atomic nucleus gives us lots of information about the element it represents. The number of protons inside the nucleus gives us the atomic number. The protons have a positive (+) charge. In order for the atom to have a neutral charge, the electrons (-) need to balance it out with their negative charge. Therefore, in a neutral atom there are just as many protons as electrons. So, if you know the atomic number and know the charge of the atom then the number of electrons is easy to find. For instance, hydrogen has 1 proton, 1+, so in order for the hydrogen atom to be neutral it must have 1- charge. Therefore, hydrogen has 1 electron.

Where do the neutrons fit in all of this? Well, neutrons are neutral. To keep it all straight I use the first letters: Neutrons are Neutral, and Protons are Positive. I then remember Electrons through the process of Elimination.

Although the neutrons do not give the atom any charge, they still hold their own weight in the importance of the atomic structure. The neutron is the largest of the subatomic particles. When you put the neutrons and protons together we get the atomic mass. The electrons are so small that their mass only counts for .01%. The electrons are not inside of the nucleus; instead they are flying around like crazy on the outside of the nucleus.

Since the atomic number gives us the number of protons in an atom and the atomic mass gives us the number of protons and neutrons, we can find the number of neutrons by subtracting the atomic number from the atomic mass.

Atomic mass - atomic number = number of neutrons.

The atomic number of an atom gives each element its identity. You can find out which element it is by its atomic number and reverse the process to find out what the atomic number is if you know which element you are working with.

Let's run through all of the numbers with an element, oxygen.

Oxygen
Atomic Number: 8
Atomic Mass: 16

From this information we can gather that oxygen has. . .

  • 8 protons (same as the atomic number)
  • There are 16 total subatomic particles in the nucleus (from the atomic mass); 8 of them are protons (atomic number), 16 particles - 8 protons = 8 neutrons.
  • A neutral oxygen atom will need to have the same number of electrons as protons to balance it out. Therefore oxygen has 8 electrons.

To unlock this lesson you must be a Study.com Member.
Create your account

Register for a free trial

Are you a student or a teacher?
I am a teacher
What is your educational goal?
 Back

Unlock Your Education

See for yourself why 10 million people use Study.com

Become a Study.com member and start learning now.
Become a Member  Back

Earning College Credit

Did you know… We have over 95 college courses that prepare you to earn credit by exam that is accepted by over 2,000 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? Study.com has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it free for 5 days!
Create An Account
Support