Write the number of periods and groups present in the modern periodic table . State the changes in valency and metallic character of elements as we move from left to right in a period. Also state the changes if any in the valency and atomic size of elements as we go down a group
Answers
7 periods
18 groups.
Period:
Valency increases, Metallic character decreases.
Group:
Valency constant, M Character increases.
The modern periodic table has 18 vertical groups. Each vertical column accomodates elements with the same number of electron in the outermost shell. These vertical columns are known as groups arranged from left to right in order of increasing atomic number. There are seven horizontal rows in the modern periodic table known as periods.
The number of shells present in an atom determines its period. For example. Elements one period have one and two peruods have two shells. The metallic character increases from left to right in periods and on moving down a group the number of electron in the outermost shells remains the same. As we go down the period valency shells increases and electron increases from left to right of the period. The group is determined by the number of electrins ptesent in the outermost shells.
Fot example sodium has atomic number 11 and its electronic configuration is 2,8,1.it has three orbits and has one electron in outermost orbit. Hence it is placed in the third period and group 1.