Learning Objective

In this lesson we will learn how elements are arranged in the periodic table, according to trends in their properties.

Learning Outcomes

By the end of this lesson you will be able to:

  • Describe the general layout of the periodic table.

  • Identify groups and periods on the periodic table.

  • Describe the distribution of solids, liquids and gases on the periodic table.

  • Describe the distribution of metals, non-metals and metalloids on the periodic table.

 

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The Periodic Table of the Elements

  • There are approximately 118 known elements, with atomic numbers 1-118.
    Elements 94-118 are synthetic elements. These do not occur naturally, but have been synthesised artificially, usually in very small quantities, because they are very unstable.
  • The periodic table of the elements is a way of organising all of these elements.
    Elements are listed in order of increasing atomic number and arranged into rows and columns.
  • The layout of the periodic table reflects trends in the properties of elements.
    For example, melting point and chemical reactivity vary in a predictable manner across and down the periodic table.
  • Each cell (square) in the periodic table includes the element’s atomic number, chemical symbol and name.

 
periodic table cell atomic number element name symbol

Each cell of the periodic table displays an element’s atomic number, chemical symbol and name.

 

Groups

  • The vertical columns of the periodic table are called groups.
    There are 18 groups, numbered 1-18.
  • Groups contain elements with similar physical and chemical properties.
    Examples
    • Group 1 (excluding hydrogen) contains the alkali metals – soft, very reactive metals.
    • Group 17 contains the halogens – non-metals whose atoms pair into molecules.
    • Group 18 contains the noble gases – odourless, colourless, very unreactive gases.
    • Groups 3 to 12 contain the transition metals.

 
periodic table group column

The vertical columns of the periodic table are called groups.

 

Periods

  • The horizontal rows of the periodic table are called periods.
    There are seven periods, numbered 1-7.
  • Periods contain elements with varying physical and chemical properties.

 
periodic table period row

The horizontal rows of the periodic table are called periods.

 

Arrangement of Groups and Periods

  • Groups and periods do not all contain the same numbers of elements.
    This gives the periodic table its unique shape, instead of it being a simple rectangle.
  • The layout of the periodic table was designed so that elements with similar physical and chemical properties were placed in the same group.
    In fact, as the periodic table was developed, many elements were predicted before they had even been discovered.

 

Solids, Liquids and Gases

  • Elements can be divided into those which are solids, liquids or gases at room temperature.
  • The majority of elements are solids.
    There are only two liquids – bromine and mercury.
    There are 11 gases, which mostly occupy the top right section of the periodic table.

 
periodic table solids liquids gases

The majority of elements are solids.

 

Metals, Non-metals and Metalloids

  • Elements can also be divided into those which are metals, metalloids (semi-metals) or non-metals.
  • The majority of elements are metals, which occupy the left and middle sections of the periodic table.
    There are 20 non-metals, which form the top right section of the periodic table (plus hydrogen on the top left).
    There are seven metalloids, which form a diagonal line between the metal and non-metal sections.

 
periodic table metals metalloids non-metals

The majority of elements are metals.

 

Summary

  • The periodic table is a way of organising all of the known elements.
    The elements are listed in order of increasing atomic number.
  • Each cell in the periodic table includes the element’s atomic number, chemical symbol, and name.
  • The layout of the periodic table reflects trends in the properties of elements.
    For example, there are general patterns in the distribution of elements based on state of matter and metallic character.
  • The vertical columns of the periodic table are called groups.
    These contain elements with similar physical and chemical properties.
  • The horizontal rows of the periodic table are called periods.
    These contain elements with varying physical and chemical properties.

 
periodic table elements

 

(Header image: Zerbor, Adobe Stock)

 

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