Introduction to Chlorine's 7th Oxidation State

The 7th oxidation state of chlorine, ClVII, represents a significant loss of electrons, manifesting as a highly charged ion. This state is critical in understanding the chemical behavior and bonding of chlorine in various compounds, particularly in perchlorates. In this article, we will explore the meaning of the 7th oxidation state of chlorine, its occurrence in perchlorate ions, and the implications of the formal charge in determining the oxidation state.

Electron Loss and Positive Charge

In the neutral state, chlorine (Cl) has an atomic number of 17, which means it has 17 electrons. When chlorine achieves an 7th oxidation state, it effectively loses seven electrons, resulting in a 7 charge. This is represented as Cl7 . The 7th oxidation state is commonly observed in compounds such as potassium perchlorate (KClO4), where chlorine is bonded to multiple oxygen atoms, leading to a high oxidation state.

Electronegativity and Bonding

The 7th oxidation state is primarily observed because of the strong electronegative nature of oxygen. In compounds like KClO4, each chlorine atom is bonded to four oxygen atoms through double bonds. Due to oxygen's high electronegativity, all the electrons in these double bonds are considered assigned to oxygen, giving each oxygen atom a formal charge of -2. As a result, the ion as a whole has a -1 charge, leaving the chlorine atom with a formal charge of 7.

Chemical Equations and Oxidation States

Chemical reactions often involve the transformation of chlorine from its standard oxidation states into the 7th state. For instance, the oxidation of chlorine can be represented by the following equation:

1/2 Cl2 4 H2O → ClO4- 8 H 7 e-

This equation highlights the formation of the perchlorate ion (ClO4-) and the simultaneous release of hydrogen ions and electrons. The perchlorate ion, ClO4-, exhibits the 7th oxidation state of chlorine, which is expressed using Roman numerals as ClVII.

Cl2O7 and Oxidation Number

The compound Cl2O7 (dichlorine heptoxide) is another example where the 7th oxidation state of chlorine is evident. In Cl2O7, each chlorine atom forms a total of seven oxygen bonds, with each oxygen atom contributing two electrons to the bond due to oxygen's high electronegativity.

Calculating the formal charge of chlorine in Cl2O7 (Clvii) involves the following steps:

Determine the number of valence electrons in a neutral chlorine atom (17 - 2 inner electrons 15 valence electrons). Each chlorine atom forms 7 bonds, giving each atom a formal charge of 7. Since there are two chlorine atoms, the total formal charge is 2 * 7 14. Since the ion has a charge of -1, the formal charge on each chlorine atom is 7 - 2 7 - 2(2) 3.

Thus, the oxidation number of chlorine in Cl2O7 is 7, as indicated by the Roman numeral VII.

Conclusion

The 7th oxidation state of chlorine, ClVII, is a significant and complex state that arises due to the loss of electrons and strong electronegativity of oxygen. Understanding this state is essential in comprehending the behavior of chlorine in various compounds and reactions. By examining the formal charge, we can accurately determine the oxidation state and chemical properties of chlorine in different contexts.

Related Concepts

Electronegativity: The tendency of an atom to attract electrons towards itself. Oxidation States: The hypothetical charge an atom would have if all bonds to atoms of different elements were completely ionic. Perchlorate Ion (ClO4-): A polyatomic ion where chlorine has the 7th oxidation state.

Keywords

chlorine oxidation state, perchlorate ion, formal charge