What is a Periodic Table? As a chemist, the Periodic Table is the most important basics you have to learn before you can start learning anything else within chemistry. It is like if you want to learn English, you must learn the alphabets. Periodic Table is just like the alphabet of chemistry. Every chemist must know and understand the Periodic Table inside out.
Periodic Table is rows and columns of elements put in sequence of various trends. They are very harmoniously synchronised that you can easily predict a lot about the element just by looking at the position it is placed on the Periodic Table.
Elements are naturally occurring chemicals and they contain atoms of only one kind. Periodic Table contains all the elements that have been discovered so far and are still being added on as more elements come to discovery. Each element has a symbol, atomic number and atomic mass. Symbol is displayed in the middle. On the top of the symbol, an atomic number is displayed and on the bottom it is the atomic mass. Atomic number shows how many protons and electrons make up one atom of this element and the Atomic mass show the mass of the nucleus of this element. The nucleus of an atom of element is made up of protons and neutrons. Elements are arranged in groups which are the columns. There are 8 groups of elements and group number tells us how reactive each element is. For example in group one the element are very reactive but in group 8 all elements are very unreactive. It is because elements of group one contain only one electron in the outer shell as they are meant to have 8 electrons. As they are 7 electrons short, they are considered to be highly reactive. Whereas in group 8, the elements contain 8 electrons in the outer shell and as they are meant to have 8, they are very much stable and therefore considered very unreactive. Group 4 elements can be reactive and unreactive equally.
There are rows of elements which tell us how many shells there are around the atoms of each element. These rows are called periods. In period one, all the elements have one shell around their atoms. For any atom to be stable it must have its shells complete of electron. Any atom with incomplete shells is likely to be reactive. The number of electron for stability is 8. If an atom has two electrons, it either must gain 6 more electrons or lose its two electrons in order to become stable. Losing two electrons are easier than gaining 6 so atom opts to lose two electrons. The number of shells determines how easily those outer electrons are lost or gained. For atoms that are looking to lose electron, having more shells means, the electrons can easily be lost as the nucleus is shielded with shells hence the element is more reactive. But for atoms that are looking to gain electron, more shells means it's difficult to gain outer electrons therefore the element becomes less reactive.
With more shells, the atom also becomes bigger; we say that the atomic radius increases with number of shells. Across the Periodic Table, the atomic radii decreases and down the group the atomic radii increases. Group 1 and 2 are classed as Metals and are also called group-S elements. Group 3 - 8 are all non-metals and are also classed as group p elements. The elements in between these groups are called the transition metals or group d elements.