Which is an outer electron configuration of a halogen? ns np ns np ns ns2 np
The correct answer and explanation is :
The correct outer electron configuration of a halogen is:
ns² np⁵
Explanation (≈300 words):
Halogens are the elements found in Group 17 (Group VIIA) of the periodic table. This group includes:
- Fluorine (F)
- Chlorine (Cl)
- Bromine (Br)
- Iodine (I)
- Astatine (At)
- Tennessine (Ts)
All halogens share a common outer electron configuration of ns² np⁵, where:
- n is the principal quantum number corresponding to the period (row) the element is in.
- s² indicates two electrons in the s orbital of the outer shell.
- p⁵ indicates five electrons in the p orbital of the same shell.
This gives halogens a total of 7 valence electrons (2 in s and 5 in p). Since a full outer shell contains 8 electrons (s²p⁶), halogens are one electron short of a noble gas configuration. This makes them highly reactive, especially with alkali metals (Group 1), which have a configuration of ns¹ and are eager to lose one electron.
When halogens gain one electron, they achieve the stable noble gas configuration (ns² np⁶), becoming negatively charged ions (anions) with a -1 charge. This high reactivity and tendency to gain one electron underlie many of their chemical properties:
- Fluorine (1s² 2s² 2p⁵): Outer configuration = 2s² 2p⁵
- Chlorine (3s² 3p⁵): Outer configuration = 3s² 3p⁵
- and so on…
Chemical Behavior:
Due to the ns² np⁵ configuration:
- Halogens form salts with metals (e.g., NaCl).
- They undergo oxidation-reduction reactions, often acting as oxidizing agents.
- They exhibit trends in reactivity: fluorine is the most reactive; reactivity decreases down the group.
In summary, the ns² np⁵ outer configuration defines the halogens’ chemical identity, dictating their valency, reactivity, and place in many essential chemical processes.