Define groups in the Modern Periodic Table. How do valency, atomic size and metallic character vary in a group?
Groups are the vertical columns present in the modern periodic table which consists of elements having similar chemical properties .
Example: Group 1 - alkali metals
In a group, all elements have the same valency. Eg all members of group 1 elements (alkali metals) are monovalent.
- Atomic size
As we move down the group, the number of shells increases and therefore, the atomic size also increases.
- Metallic character:
- For metals: As we move down the group, metals become more reactive . This is because as atomic size increases, the strength with which electrons are held by the nucleus decreases so it becomes easier for the atom to lose electrons.
- For non metals: As we move down the group, the ability to accept electrons decreases because of decreased electrostatic force. So, the non metallic character decreases.