Periodic Table
Chemistry: AQA GCSE Higher, topic 1.1.18
The Periodic Table
The periodic table is an ordered arrangement of all 118 known elements. The elements are arranged in order of their atomic number (number of protons). Every time you move an element to the right, the proton number increases by 1.
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Periods
- The table is ‘periodic’ because elements with similar properties are found at regular intervals, i.e. periodically.
- So, the rows of the periodic table are called periods.
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Groups
- Elements in the same column have the same number of electrons in their outer shell (the highest energy level).
- Columns are known as groups, and the group number equals the number of electrons an atom of that element has in its outer shell.
Predicting chemical properties
- Because all elements in a column have the same number of electrons in their outer shell, they have similar chemical properties.
- This means they will all react in similar ways.
Test yourself on Periodic Table
What is another name for the columns of the periodic table?
Helium and argon belong to the same group in the periodic table. If helium is an inert (unreactive) gas, what is argon?
What is the atomic number?
An element has an atomic number of 12. What is the atomic number of the element directly to its right in the same period?
An element is in Group 6 of the periodic table. How many electrons does it have in its outer shell?