Since the ancient times elements such as gold (Au) and Silver (Ag) etc are known to mankind. When we examine their properties they exhibit different behavior, thus the need of tabulated form of organizing elements arouse. The periodic table organizes elements according to the similarities/differences in between them.
Earlier forms of Periodic table were created by Dmitri Mendeleev in which elements were ordered in increasing order of their atomic weights. A pattern was observed which repeated itself after a period of “Eight”. Mendeleev’s table even had empty spaces left for undiscovered elements which were later discovered and fit exactly according to Mendeleev’s table . This also helped in prediction of newer elements.
Later Henry Mosley learned that it is experimentally possible to determine the atomic number of an element. Thus in today’s periodic table elements are arranged in Rows( Periods) and Groups(Columns). And also arranged according to increasing atomic number and not increasing atomic weight.
These trends can be observed in today’s form of periodic table :
1.) As one move across the Period atomic number of the element increases.
2.) The atomic radius increase from top to bottom in a Group.
3.) Number of Elements increase as we move down the periodic table
4.) Elements in a GROUP exhibit similar properties and also have same number of Valence electrons
5.) The atomic radius decrease are we move from left to right across the table .
6.) Energy required to remove an electron from an atom increases as we move left to right in the table.
7.) This energy decreases as we move down the column.
8.) The ability to form chemical bond increases as we move left to right .
9.) This ability decreases as we move down the column.
10.) When we look at the bottom of the periodic table ,there is a block of two rows of elements , Known as lanthanides and the actinides , these are also collectively known as the rare earth materials .