The Periodic Table

There are more than 100 different types of atoms that make up everything on Earth; these different types are called elements.

In the 1860s, the elements on the periodic table were organised based on their relative atomic masses and their physical and chemical properties. This was carried out by the Russian chemist, Dmitri Mendeleev.

Mendeleev arranged elements with similar properties together. For example, placing iodine after tellurium, as it had similar properties to the other elements in that group.

  • He also left gaps in the table for elements that had not yet been discovered. Once these elements were discovered, they were placed in their correct positions.

Let’s take a look at the basic structure of the periodic table of elements.

A detailed periodic table of elements showing the organisation of all known elements. The table is categorised by colour-coded groups, including alkali metals, alkaline earth metals, transition metals, metalloids, non-metals, halogens, noble gases, lanthanoids and actinoids. Each element is represented by its atomic number, symbol, name and relative atomic mass. The table is also marked with vertical columns indicating groups 1 through 8 and horizontal rows indicating periods, from 1 to 7, and horizontal groups indicating groups, from 1 to 8.. The lanthanoids and actinoids are displayed separately at the bottom. Arrows and annotations explain the information provided for each element, such as atomic mass and chemical symbol, using Hydrogen as an example.

Elements are separated into metals and non-metals.

Metals are found on the left side of the periodic table, while non-metals are found on the right side. The metals and non-metals are separated by the zig-zag line, which you can see in the periodic table below.

Groups and Periods

The columns in the periodic table are known as groups. Elements with similar properties are found in the same group. For example, elements in Group 1 generally share similar properties, such as melting points, boiling points and reactivity.

Also, the group number tells us how many electrons are in the outer shell. For example, the elements in group 1 all have one electron in their outer shell.

It is important to know the major groups in the periodic table:

  • Group 1 elements are called alkali metals – This does not include hydrogen, which is a non-metal, although it has similar properties to alkali metals)
  • Group 2 elements are called alkaline earth metals
  • Group 7 elements are called halogens
  • Group 0, sometimes known as group 8, are called noble gases
  • Elements in the central block of the periodic table are called transition metals

The rows of the periodic table are known as periods. As you move from left to right within a period, there are certain patterns. We can use the periodic table to predict the reactivity and properties of elements.

The reactivity of elements in group 1 increases as you move down the group. For example, potassium is more reactive than lithium.

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