How many valence electrons do the halogens possess?
5
6
2
1
7
The correct answer and explanation is :
The correct answer is 7.
Halogens are found in Group 17 of the periodic table, which includes elements such as fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). These elements are all highly reactive nonmetals that have seven valence electrons.
Valence electrons are the electrons located in the outermost electron shell of an atom, and they are crucial in determining the chemical behavior and reactivity of an element. The number of valence electrons in an element determines how it bonds with other elements. For halogens, having seven valence electrons means they are just one electron short of achieving a stable electron configuration, resembling the nearest noble gas. This makes halogens highly reactive, as they tend to gain one electron during chemical reactions to complete their outer electron shell and achieve the stability of a noble gas.
For example:
- Fluorine (F), the first halogen, has an electron configuration of 1s² 2s² 2p⁵, with seven electrons in its outermost shell.
- Chlorine (Cl) has an electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁵, again with seven electrons in its outermost shell.
Since they need one more electron to complete their outer shell, halogens tend to form negative ions (anions) by gaining one electron, resulting in a charge of -1. Alternatively, they can share electrons with other elements to form covalent bonds, such as in hydrogen chloride (HCl) or chlorine gas (Cl₂). This strong tendency to gain electrons or form bonds is why halogens are so reactive.
In summary, all halogens have 7 valence electrons, which is key to their reactivity and the types of chemical bonds they form.