Answer:
The periodic table is an arrangement of chemical elements based on increasing atomic numbers.
Explanation:
The periodic table is an arrangement of chemical elements in order of increasing atomic numbers. According to the modern periodic law, the properties of elements is a periodic function of their atomic numbers.
The periodic table is arranged in columns and rows. The columns are called groups of elements. All elements in the same group have the same number of electrons on their outermost shell hence they possess the same chemical behavior. Elements across a period have the same number of shells thus they have the same maximum excitation level.
There are important trends across the periodic table such as atomic radius, ionic radius, electro negativity, electron affinity, melting and boiling points, metallic properties etc. All these depend on an elements position in the periodic table. periodic properties of elements increase or decrease across the period or increase or decrease down the group as the case maybe.
Hence, just as one can easily read off the date and make predictions based on dates shown in a calendar, a chemist can read off the properties of elements and make predictions about the reactivity and physical properties of elements based on their relative position in the periodic table.
Gradual changes that occur down the group in the periodic table are called group trends and they usually very significant in discussing the properties of members of a group.
