Halogens are nonmetallic elements found in group VIIA forming -1 ions and having a valency of 7.
Halogens include fluorine (F), chlorine (Cl), bromine
, iodine (I), astatine (At), and tennessine (Ts). Halogens are highly reactive and have seven valence electrons. These elements are constantly trying to complete their octets by gaining one additional electron. They are reactive toward alkali and alkaline earth metals. They are often found in nature as ions (halides) or diatomic molecules. Halogens have high electronegativity, ionization energy, and electron affinity. They have an oxidation state of -1 and an electronic structure characterised by the P orbital containing 5 electrons so commonly they have the electronic structure Xp5 and can readily accept 1 electron to form a full outer shell.
Practice Questions
Khan Academy
MCAT Official Prep (AAMC)
Practice Exam 4 C/P Section Question 26
Key Points
• Halogens have 7 valence electrons (2 in s shell and 5 in p shell)
• They often react with alkali and alkaline earth metals to form salts
• High in electronegativity, electron affinity, and ionization energy
• They have an oxidation state of -1
Key Terms
Valence electron: an outer shell electron that can participate in chemical bonds
Ionization energy: the energy required to remove an electron from the valence shell of a gaseous atom
Electron affinity: the energy change that occurs when an atom gains an electron
Electronegativity: a measure of the ability of an atom to attract the electrons in a bond
Oxidation state: a number assigned to an element in chemical combination which represents the number of electrons lost
Electronic structure: the descriptive numerical assignments to electrons in different energy levels and spin states in an atom
Alkaline earth metals: any of the elements beryllium, magnesium, calcium, strontium, barium, and radium, occupying Group IIA (2) of the periodic table
Alkali: consist of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr) they constitute group 1
