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Science · Chemistry basics

The periodic table

Groups, periods, metals & non-metals.

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What is the Periodic Table?

The periodic table organises all known elements (pure substances made of one type of atom). Each element has a unique symbol, like O for oxygen or Fe for iron. Elements are arranged in rows called periods and columns called groups. This pattern helps scientists predict how elements behave.

Groups and Periods

Groups are the vertical columns numbered 1 to 18. Elements in the same group share similar chemical properties. Periods are the horizontal rows numbered 1 to 7. As you move across a period, properties change gradually. The group number often tells you about an element's reactivity.

Metals and Non-Metals

Most elements are metals, found on the left and centre of the table. Metals are shiny, conduct electricity, and can be bent. Non-metals sit on the right side. They are dull, brittle when solid, and poor conductors. A zigzag line separates the two types.

Special Groups

Group 1 contains alkali metals like sodium, which are very reactive with water. Group 7 holds halogens like chlorine, reactive non-metals. Group 18 has noble gases like helium, which barely react at all. Group 0 is another name for the noble gases.

Worked examples

  1. 1. Is calcium (Ca) in Group 2, Period 4 a metal or non-metal?

    1. Find calcium on the periodic table in Group 2, Period 4.
    2. Check which side of the zigzag line it sits on.
    3. Calcium is on the left side, so it is a metal.
    4. Group 2 elements are called alkaline earth metals, confirming it is a metal.

  2. 2. Why do fluorine (F) and chlorine (Cl) have similar properties?

    1. Locate fluorine and chlorine on the periodic table.
    2. Both are in Group 7, the halogen group.
    3. Elements in the same group have similar chemical properties.
    4. Fluorine and chlorine are both reactive non-metals that form similar compounds.

  3. 3. Which period is aluminium (Al) in?

    1. Find aluminium on the periodic table.
    2. Count the horizontal rows from the top.
    3. Aluminium is in the third row down.
    4. Aluminium is in Period 3.

Try it yourself

Argon (Ar) is in Group 18, Period 3. Is it a metal, non-metal, or something special?

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