Atomic number is considered to be a more appropriate parameter than atomic mass for classification of elements in a periodic table. Why?
How does metallic character of elements vary on moving from
- left to right in a period?
- from top to bottom in a group?
Give reasons for your answers.
Answer:
The properties of elements depend upon valence electrons in the atom which in turn depends on the total number of electrons, i.e., atomic number. Therefore, atomic number is a more appropriate parameter than atomic mass for classification of elements.
- On moving from left to right in a period, the metallic character decreases. This is due to an increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.
- On moving from top to bottom in a group, metallic character increases. This is because new shells are being added as we go down the group. This increases the distance between the valence shell and the nucleus.