What is electro-positivity and electro-negativity? How is it related to metallic character in the periodic table? What trends does the table show regarding this feature?
The elements that can easily lose electrons to form positive ions are called electropositive elements, for example: metals. Electropositivity is the measure of the ability of elements (mainly metals) to donate electrons to form positive ions.
The elements that can easily accept electrons to form negative ions are called electronegative elements, for example: non-metals. Electronegativity is the measure of the ability of elements (mainly non-metals) to attract electrons towards itself.
The opposite of electronegativity is electropositivity.
Down a group, the atomic size and nuclear charge increases but effect of increased atomic size outweighs the increased nuclear charge and hence electrons are less tightly held to the nucleus and can be easily removed so metallic or electropositive character increases.
Across a period, nuclear pull increases due to increase in atomic number and so atomic size decreases making it difficult for electrons to lose. So, metallic or electropositive character decreases and non-metallic or electronegative character increases.