The Periodic Table

The Periodic Table

Middle School

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Learning Objectives

• Describe the organization of the modern periodic table.

• Explain how to read an element's information on the table.

• Differentiate between periods and groups.

• Identify the properties of key chemical families or groups.

Key Vocabulary

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Periodic Table

A chart that organizes elements by their atomic number and shared chemical properties.

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Atom

The smallest unit of matter, made of a nucleus with protons, neutrons, and electrons.

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Atomic Number

The count of protons in an atom's nucleus, which is also the electron count.

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Period

A period is a horizontal row in the periodic table where elements have the same number of electron shells.

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Group

A vertical column in the periodic table with elements that share similar chemical properties.

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What is the Periodic Table?

• It is a system that organizes elements by atomic number and properties.

• Elements are arranged by increasing atomic number, which is the number of protons.

• The table grew from 63 elements in Mendeleev's time to over 100.

• Some unstable elements are man-made by bombarding elements like Uranium.

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Multiple Choice

What is the primary basis for the arrangement of elements in the modern periodic table?

• Number of neutrons

• Date of discovery

• Atomic number

• Atomic mass

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Reading an Element's Square

• The chemical symbol is a one or two-letter abbreviation for the element.

• ​The atomic number indicates the number of protons and electrons in a neutral atom.

• Atomic mass is the combined mass of all protons and neutrons in the nucleus.

• The number of neutrons is found with the formula:

  Number of neutrons = Mass number - Atomic number.

Multiple Choice

An element has an atomic number of 15 and an atomic mass of 31. How many neutrons does it have?

• 31

• 16

• 15

• 46

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Periods: The Horizontal Rows

• A period is a horizontal row on the periodic table; there are seven.

• Moving left to right, the atomic number of each element increases by one.

• A new period begins when a new energy level starts filling with electrons.

• Lanthanides and actinides fit into the larger periods 6 and 7.

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Multiple Choice

What does a new period on the periodic table signify?

• A decrease in atomic number

• The discovery of a new synthetic element

• The start of a new energy level for electrons

• The start of a new group with similar properties

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Groups: The Vertical Columns

• A group, or family, is a vertical column on the periodic table.

• Elements in a group share properties because they have similar valence electrons.

• There are 18 groups, numbered 1 to 18 from left to right.

• For group 17, the elements have 7 valence electrons in their outer shell.

Multiple Choice

Why do elements in the same group have similar chemical properties?

• They have the same atomic mass.

• They have the same number of valence electrons.

• They are in the same horizontal row.

• They have the same number of protons and neutrons.

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Properties of Specific Groups

• Group 1 alkali metals are very reactive and have one valence electron.

• Group 2 alkaline earth metals are reactive and have two valence electrons.

• Groups 3-12 are transition metals that are known to conduct electricity.

• Group 17 halogens are highly reactive nonmetals that form salts with metals.

• Group 18 noble gases are stable with a full outer shell of electrons.

Multiple Choice

An element is very stable and does not react with other elements. To which group does it most likely belong?

• Group 17: Halogens

• Group 1: Alkali Metals

• Group 2: Alkaline Earth Metals

• Group 18: Noble Gases

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Common Misconceptions

Misconception	Correction
The atomic number and atomic mass are the same thing.	Atomic number is the proton count; atomic mass is protons plus neutrons.
Elements in the same period (row) have similar properties.	Elements in the same group (column) share similar chemical properties.
All elements on the periodic table occur naturally.	Many elements are synthetically created in labs and are often unstable.

Multiple Choice

Based on its position in Group 2, what can be inferred about an alkaline earth metal's reactivity compared to an alkali metal in Group 1?

• It has the same reactivity.

• It is more reactive.

• It does not react at all.

• It is less reactive.

Multiple Choice

Explain the primary difference in how elements are organized into periods versus how they are organized into groups.

• Periods are by energy levels; Groups are by valence electrons and properties.

• Periods are vertical; Groups are horizontal.

• Periods are by valence electrons; Groups are by energy levels.

• Periods contain metals; Groups contain nonmetals.

Multiple Choice

An unknown element is a highly reactive nonmetal that combines with a metal to form a salt. Predict which group this element most likely belongs to and why.

• Group 2, because Alkaline Earth Metals are reactive.

• Group 17, because Halogens are highly reactive and form salts.

• Group 1, because Alkali Metals are highly reactive.

• Group 18, because Noble Gases are unreactive.

Multiple Choice

Element 117, Tennessine (Ts), has an atomic mass of 294. Analyze this information to determine its number of protons, electrons, and neutrons, and infer its chemical family.

• 294 protons, 294 electrons, 117 neutrons. It is a Transition Metal.

• 117 protons, 177 electrons, 117 neutrons. It is an Alkali Metal.

• 117 protons, 117 electrons, 177 neutrons. It is a Halogen.

• 117 protons, 117 electrons, 294 neutrons. It is a Noble Gas.

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Summary

• The periodic table organizes elements by atomic number into periods and groups.

• Each element's square shows its symbol, atomic number, and atomic mass.

• Periods are horizontal rows that indicate the principal energy level.

• Groups are vertical columns containing elements with similar properties and valence electrons.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

• 1

• 2

• 3

• 4