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Do Protons and Electrons Have the Same Mass? — Reading Comprehension

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MS-PS1
HS-PS1
RI.6.3
RI.7.1

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This reading passage, 'Do Protons and Electrons Have the Same Mass?', helps middle school students explore the massive difference in mass between two key subatomic particles. The passage explains that a proton has a mass of about 1.67 × 10⁻²⁷ kg, while an electron has a mass of about 9.11 × 10⁻³¹ kg—making the electron nearly 1,836 times lighter. Students learn that although protons and electrons have equal but opposite charges, only protons and neutrons significantly contribute to an atom’s mass. The passage aligns with NGSS MS-PS1-1 and supports Common Core ELA standards such as RI.6.1. It also includes eight multiple choice questions to check comprehension, a fun science fact, and accessible vocabulary for grades 5–8. This is an excellent resource for building science literacy and foundational knowledge in physical science.

CONTENT PREVIEW

"Atom (PSF)" by Pearson Scott Foresman / Wikimedia Commons.

Atoms are the basic building blocks of matter. Every atom is made of three main parts: protons, neutrons, and electrons. These particles are tiny, but they each play an important role. One big difference between them is their mass.

So, do protons and electrons have the same mass?
The answer is no—not even close.

A proton has a mass of about 1.67 × 10⁻²⁷ kilograms. An electron, on the other hand, has a mass of about 9.11 × 10⁻³¹ kilograms. That means an electron is nearly 1,836 times lighter than a proton!

Because electrons are so light, they add almost no mass to an atom. Most of an atom’s mass comes from the protons and neutrons in the nucleus. Electrons orbit the nucleus in a cloud and are important for electric charge and chemical reactions, but not for weight.

Even though electrons and protons are very different in mass, they have equal but opposite charges. A proton has a positive charge (+1), while an electron has a negative charge (–1). In most atoms, the number of protons and electrons is the same, which keeps the atom electrically neutral.

Understanding the difference in mass between protons and electrons helps scientists study atoms, build models, and explain how matter works at a tiny level.

Fun Fact: If a proton weighed as much as a bowling ball, an electron would weigh less than a paperclip’s tiniest shaving!

What is the main idea of the passage?

Electrons and protons are the same sizeElectrons and protons have very different massesElectrons are heavier than neutronsProtons are not found in atoms

What is the mass of a proton?

1.00 kg9.11 × 10⁻³¹ kg1.67 × 10⁻²⁷ kg2.00 × 10⁻²⁴ kg

What is the mass of an electron?

1.67 × 10⁻²⁷ kg9.11 × 10⁻³¹ kg0.01 kg1.00 × 10⁻²³ kg

Which particle is lighter?

ProtonNeutronElectronThey all weigh the same

How many times lighter is an electron compared to a proton?

About 2 timesAbout 10 timesAbout 100 timesAbout 1,836 times

Why don't electrons add much to the atom's mass?

They are outside the atomThey are much smaller than protons and neutronsThey are always movingThey have a neutral charge

What is the charge of a proton and an electron?

Both are positiveProton is positive, electron is negativeProton is negative, electron is neutralBoth are neutral