Introducing KNOVA — A free reading app with curriculum-aligned passages on History & Science for Grades 3-8Learn More →

Nucleus of the Atom — Reading Comprehension

No ratings yet

Premium Resource

Grades

Standards

MS-PS1-1

Rate this resource

Send Feedback / Report an Issue

About This Reader

This comprehensive passage for grades 6-8 introduces students to the nucleus of the atom, the dense center that contains protons and neutrons and holds nearly all the atom's mass. Students will explore the mechanisms that give the nucleus its properties, how it relates to atomic structure, and its impact on real-world phenomena like nuclear energy and isotopes. The passage is aligned with NGSS MS-PS1-1, emphasizing the interactions and systems that make up matter. Accompanying activities include a glossary, multiple-choice quiz, writing prompts, and graphic organizers, all designed to strengthen understanding and academic vocabulary. Spanish translations and differentiated versions are provided, along with integrated audio support. This resource helps students connect atomic structure to broader scientific principles and applications.

CONTENT PREVIEW

Atoms are the building blocks of all matter in the universe, from the air we breathe to the stars in distant galaxies. At the center of every atom lies the nucleus, a tiny region that holds almost all the atom's mass. Although the nucleus is extremely small compared to the entire atom, it is packed with positively charged protons and neutral neutrons. This dense core is what gives each atom its unique identity and determines how it interacts with other atoms.

Structure and Composition of the Nucleus

The nucleus is made up of two main particles: protons and neutrons. Protons carry a positive electrical charge, while neutrons have no charge at all. These particles are held together by the strong nuclear force, one of the four fundamental forces in nature, which is much stronger than the repulsive force between positive charges. Even though the number of protons and neutrons varies between elements, the nucleus always contains nearly all of the atom's mass. For example, in a hydrogen atom, the nucleus is about 100,000 times smaller than the whole atom, yet it accounts for more than 99.9% of its mass. If the atom were the size of a sports stadium, the nucleus would be the size of a marble at the center of the field.

Function and Importance of the Nucleus

The arrangement of protons in the nucleus determines the atomic number of the element, which defines what kind of atom it is (like hydrogen, carbon, or oxygen). The number of neutrons can vary, creating different isotopes of the same element. Changes in the nucleus, such as the splitting (fission) or combining (fusion) of nuclei, release enormous amounts of energy. This nuclear energy powers the sun and can be harnessed for electricity in nuclear power plants. The stability of the nucleus also plays a key role in radioactive decay, a process used in medicine and archaeology to date ancient materials.

Scientific Discovery and Broader Implications

Scientists have learned about the nucleus through experiments like the famous gold foil experiment, which showed that most of the atom is empty space with a dense center. Understanding the nucleus has led to advances in technology, from nuclear medicine that treats diseases to smoke detectors that keep homes safe. The study of nuclei also connects to larger scientific principles, such as the conservation of mass and energy, and helps explain the origin of elements in stars.

In summary, the nucleus is a small but mighty part of the atom, responsible for its mass, structure, and many properties. Its discovery and study have shaped our understanding of the universe and continue to inspire scientific breakthroughs.

Interesting Fact: If the atom were blown up to the size of a football stadium, the nucleus would still be no bigger than a marble—yet it would contain nearly all the atom’s mass!

What is located at the center of every atom?

The nucleusThe electron cloudThe moleculeThe proton only

Which particles are found in the nucleus?

Protons and neutronsElectrons and protonsNeutrons and electronsOnly protons

What percentage of an atom’s mass is in the nucleus?

More than 99.9%About 50%Less than 1%Around 10%

What force holds protons and neutrons together in the nucleus?

Strong nuclear forceGravitational forceElectromagnetic forceFriction force

In the passage, what analogy is used to describe the size of the nucleus compared to the atom?

A marble in a stadiumA planet in spaceA drop in the oceanA pebble on a beach

What determines the identity (element) of an atom?

Number of protonsNumber of neutronsNumber of electronsMass of the atom