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

Organizing the Elements — Reading Comprehension

No ratings yet

Premium Resource

Grades

Standards

MS-PS1-1

Rate this resource

Send Feedback / Report an Issue

About This Reader

This passage for middle school science explores how scientists organized the elements as more were discovered, leading to the modern periodic table. Students will learn about early attempts to sort elements by properties, the creation of periods (rows) and groups/families (columns), and how this organization reveals repeating patterns in matter’s behavior. The passage covers the cause-and-effect relationships that led to the development of the table and highlights real-world applications, including how the periodic table is used in technology and medicine. It is aligned to NGSS MS-PS1-1 and features audio integration, Spanish translations, a glossary, differentiated reading levels, quizzes, writing prompts, and graphic organizers to support comprehension and critical thinking about systems and patterns in science.

CONTENT PREVIEW

"Simple Periodic Table Chart-en" by Offnfopt / Wikimedia Commons (Public domain).

Chemical elements make up all matter, from the air we breathe to the metals in our phones. As scientists discovered more elements, they faced a problem: how could they keep track of so many different substances and their properties? The solution was to develop a system for organizing the elements, which led to the creation of the periodic table. This table helps scientists predict how elements will behave and interact, making it a powerful tool for understanding the natural world.

Early Attempts and the Need for Order

In the early 1800s, only about 30 elements were known. Scientists noticed that some elements shared similar properties, such as how they reacted with water or their appearance. Early chemists, like Johann Döbereiner, grouped elements in threes, called triads, based on similar behaviors. However, as more elements were discovered, these simple groupings became less effective. By the mid-1800s, over 60 elements had been identified, each with different atomic masses and characteristics. The need for a comprehensive organizational system became urgent to avoid confusion and to reveal patterns among the elements.

The Periodic Table: Periods and Groups

Dmitri Mendeleev, a Russian chemist, made a breakthrough in 1869. He arranged elements in order of increasing atomic mass and noticed that certain properties repeated at regular intervals. By placing elements with similar properties into vertical columns called groups or families, and horizontal rows called periods, Mendeleev’s periodic table revealed a repeating pattern—what scientists call periodicity. For example, sodium and potassium are both shiny metals that react strongly with water and are found in the same group. In contrast, noble gases like neon and argon, which are very stable and unreactive, form another group. Today, the periodic table includes over 110 elements, arranged by their increasing atomic number (the number of protons in each atom).

Patterns and Predicting Element Behavior

The periodic table does more than organize elements; it helps scientists predict how elements will react or combine. For example, elements in the same group often form similar compounds because they have the same number of valence electrons. The table also shows trends, such as increasing reactivity or changes in state (solid, liquid, gas) across a period. These patterns are not random—they are caused by the arrangement of electrons and the structure of atoms. Modern scientists use these patterns to discover new materials and design safer medicines. The periodic table’s structure shows the underlying system in nature and connects to the broader scientific principle that the properties of matter are determined by atomic structure.

Today, the periodic table is a living document, updated as new elements are discovered. Its organization continues to guide scientific research, environmental safety, and technological innovation. Understanding how the elements are arranged helps us appreciate the order and predictability found in the natural world.

Interesting Fact: Every element heavier than uranium (element 92) has been made by scientists in laboratories, not found naturally on Earth.

What problem did scientists face as more elements were discovered?

They could not keep track of the different elements and their properties.They ran out of names for new elements.They found too many elements in nature.They could not create new elements in labs.

Who created the first widely accepted version of the periodic table?

Dmitri MendeleevJohann DöbereinerMarie CurieIsaac Newton

What is a group (or family) in the periodic table?

A vertical column of elements with similar propertiesA horizontal row of elementsA set of three elementsA list of all metals

What does 'periodicity' mean in the context of the periodic table?

The repeating patterns of properties in elementsHow often scientists study elementsThe time it takes to discover new elementsThe number of elements in a period

Which property do elements in the same group usually share?

The same number of valence electronsThe same atomic numberThe same colorThe same mass

What is the main benefit of organizing elements in the periodic table?

It helps predict how elements will react.It shows how elements look.It makes elements easier to spell.It shows how elements are made.

Which of the following is an example of a group mentioned in the passage?

Noble gases like neon and argonMetals and nonmetalsSolid, liquid, and gasScientists and chemists

True or False: The periodic table is only useful for chemistry, not for technology or medicine.

TrueFalse

True or False: Every element heavier than uranium is found naturally on Earth.

TrueFalse

What are periods in the periodic table?

Horizontal rows where properties change in a patternVertical columns of similar elementsGroups of three elementsRandomly ordered elements