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Last Updated: 14th June 2023
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What is the Periodic Table?
Keywords
Periodic Table, Dimitri Mendeleev, table of elements, properties, patterns, atomic weight, reactivity, non-reactive, series, valence shell, Lothar Meyer, groups, alkali, boron, carbon, nitrogen, chalcogen, halogen, noble.
Introduction
We talk about the periodic table as though it's something we sit at and eat our lunch to. We don't, but we do look at it's marvel in the fact that every element known to man is listed on it. From this, we can make compounds, mixtures and more. Everything that is man-made in the world is made up from one of the basic elements in this table.
A Bit of History
The modern periodic table as we see it today (which reads like a map to some people), was designed in 1869 by Dimitri Mendeleev. He was a Russian chemist who was playing with the then known elements, and discovered that some had similar properties.
From this, he was able to group them together, and started to formulate a way to classify them into some sort of table. He also knew there must have been more elements that were undiscovered, and when he put the table together, he left spaces for them.
The periodic table was sorted into and order of increasing atomic weight, where the table then showed a similar pattern, called a periodicity, of properties within groups of elements.
Interesting fact: although Dimitri Mendeleev is cited at being the modern founder of the way the periodic table looks, he wasn't the first to make one. In 1864, Lothar Meyer published a periodic table that described the placement of 28 elements.
Now, we use the periodic table as if it's second nature, and this helps us to figure out experiments, create compounds and mixtures from the same or opposite groups, and to see which elements may be compatible with others.
The Periodic Table Now
There are 118 elements in the periodic table, and they are all classed in rows and columns on the table. The columns signify which group they are in:
- Group 1: Alkali metals
- Group 2: Alkaline Earth metals
- Group 13: Boron group
- Group 14: Carbon group
- Group 15: Nitrogen group
- Group 16: Chalcogens, otherwise known as the Oxygen group
- Group 17: Halogens
- Group 18: Noble gases
Here's a YouTube video from Cognito on the Periodic Table:
Each group has shared properties that can be studied in more detail. There are two elements along the top of the table - Hydrogen and Helium. They are special elements. Here's why:
Hydrogen: only has one proton and one electron, and doesn't have a single neutron in its neutral form.
Helium: unique among the elements, it only has two electrons in its outer orbital, also known as a valence shell. It is put in Group 18, as it shares one characteristic with the other elements in the group - it has a full valence shell.
Where Does the Term Period Come From?
A period in the table is simply each row in the table. From left to right, it is called a period. This means each element in the same row share similar electron configurations.
If you know how many atomic orbitals an element has, you should be able to figure out which row that element is in, and therefore know what period it is in.
Dmitri Mendeleev
