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Atoms and the Periodic Table

8th grade nonfiction passage about chemistry: 288 words, eight questions, an answer key and vocabulary.

8th grade nonfiction chemistry 288 words

Atoms and the Periodic Table

Everything you can touch, from a coin to the air in a balloon, is made of atoms. An atom is the smallest piece of an element that still has the properties of that element. Atoms are far too small to see, even with an ordinary microscope.

An atom has three kinds of particles. Protons carry a positive charge, and neutrons carry no charge. Both are packed into a tiny center called the nucleus. Electrons carry a negative charge and move around the nucleus in the space outside it. Most of an atom is empty space.

What makes one element different from another is the number of protons in its atoms. Every atom of hydrogen has one proton. Every atom of carbon has six, and every atom of oxygen has eight. This number is called the atomic number. If an atom gains or loses a proton, it becomes a different element.

The periodic table arranges all the known elements in order of atomic number. Each row is called a period, and each column is called a group. Elements in the same group tend to behave in similar ways. For example, the noble gases, such as helium and neon, rarely react with other elements, while the alkali metals, such as sodium and potassium, react easily.

The table also helps scientists predict. When Dmitri Mendeleev arranged the elements, he left gaps for elements that no one had found yet, and he predicted what they would be like. Later discoveries matched his predictions closely.

Atoms can join together. When atoms of different elements bond, they form a compound, such as water, which is made of two hydrogen atoms and one oxygen atom. Chemists use the table to understand how atoms will combine.

Questions

  1. What is an atom? in the text

  2. What are the three kinds of particles in an atom, and where is each found? in the text

  3. What decides which element an atom belongs to? in the text

  4. How many protons does an atom of oxygen have? in the text

  5. How is the periodic table arranged? in the text

  6. What do elements in the same group have in common? in the text

  7. Why did Mendeleev leave gaps in his table? think about it

  8. According to the passage, what would happen to an atom of carbon if it gained two protons? think about it

Words to know

atom
the smallest piece of an element that still has that element's properties
nucleus
the tiny center of an atom, made of protons and neutrons
proton
a particle in the nucleus with a positive charge
electron
a tiny particle with a negative charge that moves around the nucleus
atomic number
the number of protons in an atom of an element
compound
a substance made when atoms of different elements join together

How to use it

  1. Press Read it big (or B) to put the text on the projector, or Full screen (F) to fill the whole screen.
  2. Ask the questions one at a time and use Show answer when the class has decided. A shows or hides every answer.
  3. Print student copy for the class, or Print with answers for yourself.

Ideas for class

  • Before reading, put atom, nucleus, proton, electron, atomic number and compound on the board with their meanings from the Words to know section and have students predict what the text will be about.
  • Read it aloud once while students follow along, then have them reread it alone or with a partner. At a calm 100 words a minute it takes about 3 minutes to read aloud.
  • Use the Read it big button (or B) to put the text on the projector, and Show answer on one question at a time so the class commits to an answer first.
  • Question 7 asks the reader to infer. Ask students to point to the words in the passage that led them to their answer.
  • Ask students to write one question the passage did not answer, then look for the answer in a book or on a classroom screen.
  • Print the student copy for independent work and keep the answer-key copy for yourself.

Related

Questions

What reading level is "Atoms and the Periodic Table"?

It was written for 8th grade. It has 288 words and works out to a Flesch-Kincaid grade level of about 7.9. That is a formula's estimate from sentence length and syllables, and it is not a Lexile or a guided reading level, so check it against your students.

What do the questions ask?

There are eight. 6 ask for something the text says directly and 2 ask the reader to work something out from clues. Each has an answer in the key, and the answers are written as a teacher would accept them, not as the only possible wording.

How long does it take to read?

About 3 minutes read aloud at 100 words a minute. For a one-minute fluency check, paste it into the fluency timer and use the word count.

Can I print it?

Yes. Print student copy gives the passage, the questions with lines to write on, and the word meanings. Print with answers gives the same page with the answers filled in. Both are made in your browser.

Is this passage from a published book?

No. It was written for Peabody Teach, so there is no book to buy and no login to read it.

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