Chemistry: PERIODIC TABLE
Periodic table refers to a table in which all the elements present on the earth are arranged in order of their increasing atomic number and increasing atomic mass. The elements are arranged in left to right order that means as you move from left side to the right side of the periodic table the atomic number of the elements will go on increasing.
Atomic number of an element is the sum of the protons present in it. The different rows present in a periodic table are called periods. The period number of the element represents the highest level of energy that an electron can occupy in the atomic structure of that element. The number of electron increases as you navigate down a periodic table and its energy level increases along with the sub levels of energy. When an electron moves from its original stage to a higher energy level it requires more energy but when it travels down from one energy level to a lower energy level it looses energy.
From a periodic table, you can get information about the nature, reactivity and other information about the different elements present in a periodic table. For instance, you can easily calculate the number of carbon atoms present in 1 kg of carbon. You can judge easily from the reactivity of element weather it is a metal or non-metal. The behaviour of the elements changes as you move from metal towards non-metals. All the elements present in same column of a periodic table are called a group.