What are the salient features of Modern
Answer: In a period of the periodic table, the number of valence electrons increases as atomic number increases. As a result, elements change from metal
to metalloid to nonmetal to noble gas.
Atomic size is a periodic property. As atomic number increases in a period, atomic radius decreases. As atomic number increases in a group, atomic radius increases.
Positive ions have smaller atomic radii than the neutral atoms from which they derive. Negative ions
have larger atomic radii than their neutral atoms.
Positive ions in the same group increase in size down the group.
In a group, each element has the same number of valence electrons. As a result, the elements in a group show similar chemical behaviour.
Metallic character decreases from left to right in a period because of the increase in the effective nuclear charge.
Non-metallic character increase from left to right in a period because of increase in
effective nuclear charge.Non-metallic character decreases down the group because of increase in the size of the