Which is the most active halogen? Which is the least active?
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The bigger the radius, the less the 8th electron is attracted, so I is the least reactive, and F the most.
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Halogens are elements in Group 17 in the periodic table of the elements. Their valence shells already contain seven electrons, so they only need one electron each to complete the valence shell and become stable. Consequently, they are described as very reactive nonmetals.
Nonmetallic activity is based on the ability to gain (attract) electrons. The smaller the atom (least number of electron shells), the stronger the attraction between (negative) valence electrons and the positive nucleus.
The larger the atom (greatest number of electron shells), the weaker the attraction between (negaive) valence electrons and the positive nucleus.
The most reactive halogen is fluorine (F) that has only two shells and whose valence electrons are in the second shell.
The least reactive halogen is iodine (I) that has five shells and whose valence electrons are in the fifth shell.
Nonmetallic activity is based on the ability to gain (attract) electrons. The smaller the atom (least number of electron shells), the stronger the attraction between (negative) valence electrons and the positive nucleus.
The larger the atom (greatest number of electron shells), the weaker the attraction between (negaive) valence electrons and the positive nucleus.
The most reactive halogen is fluorine (F) that has only two shells and whose valence electrons are in the second shell.
The least reactive halogen is iodine (I) that has five shells and whose valence electrons are in the fifth shell.