How Atoms Differ — Reading Comprehension

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Grades

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MS-PS1-1

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This middle school science reading passage, aligned with NGSS standard MS-PS1-1, explores the fundamental differences among atoms. Students will learn the scientific mechanisms behind isotopes—atoms of the same element with different numbers of neutrons—and ions, which are atoms that have gained or lost electrons and become charged. The passage explains why atoms of different elements behave uniquely, focusing on how their atomic structure determines chemical properties and reactions. Real-world examples, such as carbon isotopes and sodium ions, are included to connect the science to everyday life and technology. The resource also features a glossary, differentiated reading versions, Spanish translations, multiple-choice questions, writing prompts, and graphic organizers. Audio integration is available to support diverse learners. This comprehensive resource helps students understand the foundational concepts of atomic structure and prepares them for deeper explorations in chemistry and physical science.

CONTENT PREVIEW

Atoms make up everything in the universe, from the air we breathe to the water we drink. Even though all atoms are built from the same three particles—protons, neutrons, and electrons—not all atoms are identical. The differences between atoms help explain why elements have unique properties and why some atoms behave in special ways. Understanding these differences is crucial for exploring the structure and behavior of matter.

Isotopes: Same Element, Different Neutrons

Atoms of the same element always have the same number of protons. For example, every carbon atom has 6 protons. However, atoms can have different numbers of neutrons. These variations are called isotopes. Isotopes of an element have the same chemical behavior because they have the same number of protons and electrons, but their mass is different. For example, carbon-12 and carbon-14 are both forms of carbon, but carbon-12 has 6 neutrons while carbon-14 has 8 neutrons. Scientists use isotopes in fields like medicine (for cancer treatment) and archaeology (for dating ancient objects using radioactive carbon).

Ions: When Atoms Gain or Lose Electrons

Atoms are normally neutral, with equal numbers of protons and electrons. Sometimes, an atom can gain or lose electrons. This process creates ions, which are atoms with an electric charge. If an atom loses one or more electrons, it becomes a positively charged ion (cation). If it gains electrons, it becomes a negatively charged ion (anion). For example, a sodium atom (Na) loses one electron to become Na⁺, which is essential for nerve signals in your body. Chlorine gains an electron to become Cl^-, making table salt (NaCl) when it joins with sodium ions.

Why Different Elements Behave Differently

The number of protons in an atom's nucleus determines its element. Each element has a unique number of protons, called its atomic number. This difference in atomic number causes different arrangements of electrons, which affect how atoms interact in chemical reactions. For example, oxygen atoms can attract electrons more strongly than hydrogen atoms. This property helps water form and gives it unique characteristics. Elements like helium are stable because their outer electron shells are full, while others, like sodium, are more reactive. These behaviors are explained by the periodic table, which organizes elements by their atomic structure and properties.

In summary, atoms differ in the number of neutrons (isotopes) and in their electric charge (ions). These differences help explain why elements react differently and why the world is made up of such a variety of materials. Scientists continue to study atoms to unlock new technologies, improve healthcare, and understand our universe on the smallest scale.

Interesting Fact:
Some isotopes are unstable and release energy as radiation. Carbon-14 is used by archaeologists to date fossils and ancient remains up to 50,000 years old!

What are the three main particles that make up an atom?

Protons, neutrons, and electronsNeutrons, molecules, and ionsElectrons, elements, and compoundsProtons, molecules, and anions

What do all atoms of the same element have in common?

The same number of protonsThe same number of neutronsThe same massThe same electric charge

Which of the following best describes an isotope?

Atoms with different numbers of protonsAtoms with different numbers of electronsAtoms with different numbers of neutronsAtoms with different atomic numbers

What is an ion?

An atom with no chargeAn atom that has gained or lost electronsAn atom with more protons than neutronsAn atom with the same number of protons as electrons

How does the periodic table organize elements?

By their atomic number and propertiesBy their colorBy their massBy their size

In the passage, what is a cation?

A positively charged ionA negatively charged ionA type of isotopeAn atom with extra neutrons

Why do sodium and chlorine form table salt?

Because both are isotopesBecause sodium loses an electron and chlorine gains it, making ions that join togetherBecause both are neutral atomsBecause they have the same number of protons

Which statement is supported by the passage?

Atoms of the same element can have different numbers of neutronsAll atoms have the same number of protons and neutronsElectrons are found in the nucleusIsotopes have different chemical properties

Atoms can become ions by gaining or losing electrons. (True/False)

TrueFalse

All isotopes of an element have the same number of protons. (True/False)

TrueFalse