Listen&Learn: The periodic table

Learn about the system scientists use to organize chemical elements

Pre-listening vocabulary

• classify: to sort something into a group
• element: a substance made up of one kind of atom
• property: a trait or characteristic of something
• outlier: something that doesn’t follow an expected pattern
• subatomic: smaller than an atom
• orbit: to move in circles around something
• nucleus: the centre of an atom

Listening activity

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Gapfill exercise

The periodic is a system that scientists use to and classify chemical elements. Originally, many scientists tried to sort the elements by properties. One of the early models of the periodic table sorted elements by atomic weight, which naturally grouped elements with properties together. However, certain elements were outliers, and did not fit in their groups. In 1898, a scientist named J.J. Thomson discovered the electron, a subatomic particle with a charge. Later, in 1911, a scientist named Ernest Rutherford learned that electrons orbit a nucleus, which makes up most of the atom’s mass. Inside the nucleus, there are protons, which have a positive charge. An atom has an number of electrons and protons. This number became known as an element’s atomic number. Today, elements on the periodic table are arranged by atomic number, which gives a more accurate understanding of element properties.

Comprehension questions

See answers below

1. An early model of the periodic table sorted elements by
   a. atomic number
   b. atomic weight
   c. number of subatomic particles
   
2. The first subatomic particle to be discovered was
   a. the electron
   b. the proton
   c. the neutron
   
3. A proton has
   a. a positive charge
   b. a negative charge
   c. no charge

Discussion/essay questions

1. Even though scientists did not yet understand subatomic particles, the early model that put elements in order of atomic weight still naturally grouped similar atoms together. Why do you think this is? Do you know any other historical examples of humans finding patterns that they didn’t understand?

Transcript

The periodic table is a system that scientists use to organize and classify chemical elements. Originally, many scientists tried to sort the elements by properties. One of the early models of the periodic table arranged elements by atomic weight, which naturally grouped elements with similar properties together. However, certain elements were outliers, and did not fit in their groups. In 1898, a scientist named J.J. Thomson discovered the electron, a subatomic particle with a negative charge. Later, in 1911, a scientist named Ernest Rutherford learned that electrons orbit a nucleus, which makes up most of the atom’s mass. Inside the nucleus, there are protons, which have a positive charge. An atom has an equal number of electrons and protons. This number became known as an element’s atomic number. Today, elements on the periodic table are arranged by atomic number, which gives a more accurate understanding of element properties.

Answers to comprehension questions

1b 2a 3a