Across a period I.E increases progressively from left to right
Explanation:
The trend of the first ionization energy is such that across a period I.E increases from left to right due to the decreasing atomic radii caused by the increasing nuclear charge. This not compensated for by successive electronic shells.
Ionization energy is a measure of the readiness of an atom to lose an electron.
The lower the value, the easier it is for an atom to lose an electron.
Elements in group I tend to lose their electrons more readily whereas the halogens hold most tightly to them.
The first ionization energy is the energy needed to remove the most loosely bonded electron of an atom in the gaseous phase.
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