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2.30: Protons

Difficulty Level: At Grade Created by: CK-12
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This glowing sphere represents the sun, which has a diameter of 1.4 × 10 9 meters. The sun has a special relationship to another object that is only about 1.7 × 10 -17 meters in diameter—the subatomic particle called the proton. How is the gigantic sun related to the extremely tiny proton? Read on to find out.

What Is a Proton?

A proton is one of three main particles that make up the atom. The other two particles are the neutron and electron. Protons are found in the nucleus of the atom. This is a tiny, dense region at the center of the atom. Protons have a positive electrical charge of one (+1) and a mass of 1 atomic mass unit (amu), which is about 1.67 × 10 -27 kilograms. Together with neutrons, they make up virtually all of the mass of an atom. For an excellent video on protons and other fundamental particles in atoms, go to this URL:

http://www.youtube.com/watch?v=Vi91qyjuknM (7:44)

Q: How do you think the sun is related to protons?

A: The sun’s tremendous energy is the result of proton interactions. In the sun, as well as in other stars, protons from hydrogen atoms combine, or fuse, to form nuclei of helium atoms. This fusion reaction releases a huge amount of energy and takes place in nature only at the extremely high temperatures of stars such as the sun.

Identical Protons, Different Elements

All protons are identical. For example, hydrogen protons are exactly the same as protons of helium and all other elements, or pure substances. However, atoms of different elements have different numbers of protons. In fact, atoms of any given element have a unique number of protons that is different from the numbers of protons of all other elements. For example, a hydrogen atom has just one proton, whereas a helium atom has two protons. The number of protons in an atom determines the electrical charge of the nucleus. The nucleus also contains neutrons, but they are neutral in charge. The one proton in a hydrogen nucleus, for example, gives it a charge of +1, and the two protons in a helium nucleus give it a charge of +2. To learn more about the relationship between protons and elements, go to this URL:

http://www.youtube.com/watch?v=lP57gEWcisY (1:57)

Q: There are six protons in each atom of carbon. What is the electrical charge of a carbon nucleus?

A: The electrical charge of a carbon nucleus is +6.

What Are Protons Made of?

Protons are made of fundamental particles called quarks and gluons. As you can see in the Figure below , a proton contains three quarks (colored circles) and three streams of gluons (wavy white lines). Two of the quarks are called up quarks (u), and the third quark is called a down quark (d). The gluons carry the strong nuclear force between quarks, binding them together. This force is needed to overcome the electric force of repulsion between positive protons. Although protons were discovered almost 100 years ago, the quarks and gluons inside them were discovered much more recently. Scientists are still learning more about these fundamental particles. You can take an animated tour of the atom, including protons and their fundamental particles, at this URL: http://education.jlab.org/atomtour/index.html .

Summary

  • A proton one of three main particles that make up the atom. It is found in the nucleus. It has an electrical charge of one +1 and a mass of 1 atomic mass unit (amu).
  • Atoms of any given element have a unique number of protons that is different from the numbers of protons of all other elements.
  • Protons consist of fundamental particles called quarks and gluons. Gluons carry the strong nuclear force between quarks, binding them together.

Vocabulary

  • proton : Positively charged atomic particle inside the nucleus of an atom.

Practice

Do the activity at the URL below for a better appreciation of the size of a proton.

http://www.pbs.org/wgbh/nova/teachers/activities/pdf/3012_elegant_13.pdf

Review

  1. Describe protons.
  2. What is the relationship between protons and elements?
  3. Atoms, which are always neutral in electric charge, contain electrons as well as protons and neutrons. An electron has an electrical charge of -1. If an atom has three electrons, infer how many protons it has.
  4. Identify the fundamental particles that make up a proton.

Vocabulary

proton

proton

Positively charged atomic particle inside the nucleus of an atom.

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Description

Difficulty Level:

At Grade

Concept Nodes:

Grades:

7 , 8

Date Created:

Oct 31, 2012

Last Modified:

Nov 12, 2014
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