Periodic Table

We know that elements are types of atoms, made up of varying numbers of protons, neutrons, and electrons. Scientists have discovered or made about 120 elements. The periodic table is a little like a cookbook. It is a list of all known elements and their composition.

What are the different groups in the periodic table?

  • There are eight main groups (indicated in the picture above as 1, 2, 13, 14, 15, 16, 17, 18).
  • Each element within the group has similar chemical properties as the other elements in its group.
  • All elements that belong to the same group have the same number of electrons in their outer orbit or shell

Fun Facts

  • The periodic table is a grid with columns that run left to right (horizontal) and columns that run up and down (vertical).
  • The elements are organized in cycles or periods from left to right, based on the number of protons in their nucleus.
  • Elements are also organized in groups, based on their characteristics. The far left column contains alkali metals, for example. Inert noble gases are grouped in another column.
  • Each element has an abbreviation. Some elements, like Hydrogen, which is H, are easy to remember. Others have abbreviations based on Latin names, which make them harder to remember. Gold’s abbreviation is Au, after the Latin word for gold, aurum.



Element: A type of atom

Periodic table: A grid or graph that organizes and names the elements


Q and A

Question: Who developed the periodic table?

Answer: The periodic table was first proposed in 1869 by Dmitri Mendeleev, a Russian chemist.


Question: How do scientists use the periodic table?

Answer: Scientists use the periodic table for many purposes. Because similar elements are grouped together, scientists know how they might react when mixed with other elements in a lab.


Question: What is a period?

Answer: Each horizontal row is known as a period. There are seven periods in total.
n = 1 is recognised as period 1 and so on.


Atomic number: this can be identified by looking at the elements position on the periodic table.
Mass number: in many periodic tables the mass number is the number indicated under the symbol on the periodic table.
Number of neutrons: To calculate the number of neutrons in an atom, subtract the atomic number from the mass number


Question: How to show electrons in an atom

Answer: 1.Find the Atomic number of the element (e.g helium = 2)
2.Subtracted the mass number from the atomic number in order to calculate the number of neutrons (e.g helium 4-2=2)
3.As Helium on the first period of the periodic table it only has one orbit n = 1.
4.However, if we were calculating e.g argon which has an atomic number of 18, mass number of 40 and thus 22 neutrons (40-18).


Question: How do we tell how many orbits there are and how may electrons go on each orbit?


  • Basically, we look at the periods of the periodic table.
  • Period one has 2 electrons, this means that n =1 (orbit one) has 2 electrons
  • Period two has 8 electrons, this means n = 2 (orbit two) has 8 electrons
  • Period three (containing argon), has 8 electrons up until argon (you only include the electrons up until the element you are trying to figure out). This means that n = 3 (orbit three) has 8 electrons
  • This means that Ar = 2, 8, 8 which equals 18 (its total number of electrons)


The Periodic Table Worksheet

Match the chemical element symbol with its chemical element name