The elements of the group 13 – 18 come under the p – block elements. In these elements the last electron enters in the outermost p – orbital. They have ns2np1-6 electronic configuration in valence shell, helium being an exception. These elements show the maximum oxidation state equal to the sum of electrons in the outermost shell or valence shell. Most of the elements of the p – block form covalent compounds although some elements form ionic compounds (such as halogens) and coordination compounds as well. p-block contains elements which are either metals, non – metals or metalloids. p-block elements include the group of halogens and inert gases. First member of each family of the p-block elements is given below in the table with their general electronic configuration and oxidation states. p-block has the most electronegative element which is fluorine. Elements of p-block generally form acidic oxides. Many elements such as C, Si, Ge, O, N etc. also show phenomenon of allotropy. Property of catenation is also shown by many elements.
We have covered the Boron Family (Group -13 elements), the Carbon Family (Group – 14 elements), the Nitrogen Family (Group – 15 elements) and the Oxygen Family (Group – 16 elements) in other articles based on p-block elements. In this article, we will cover the Halogen Family or Group 17 Elements of p-block elements (Class XII, Chemistry).
Group 17 is the fifth group of p-block elements. The word Halogens is made up of two Greek words Halo and genes. Halo means salt and genes means born, thus halogen means salt producers. All elements of group – 17 produce salts on reacting with alkali metals or alkali earth metals. That’s why this group is also known as the Halogen family and this group elements are called halogens.
Anomalous Properties of Fluorine
Fluorine differs from other elements of the group – 17 due to its high electronegative character, small size, low F-F bond dissociation enthalpy and high ionization enthalpy.
Fluorine mostly shows exothermic reactions.
It forms only one oxoacid while other elements of the group – 17 form many oxoacids.
Hydrogen fluoride is liquid while other hydrogen halides are gases. fluorine forms a very strong bond with hydrogen due to its small size and high electronegative nature.
d- orbitals are not found in the valence shell of the fluorine atom.
An oxoacid is an acid that contains oxygen. Oxoacids of halogens contain oxygen, hydrogen and halogen atoms. For examples, HOF, HOCl, HOBr, HOI etc.
Fluorine forms only one oxoacid which is HOF due to its high electronegativity and small size.
Most of the oxoacids of halogens are not stable. They are stable either in aqueous solution or in the form of their salts. Structure of few oxoacids of chlorine are given below –
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Interhalogens compounds are those compounds which are formed by the reaction of two different halogens. They can be assigned general compositions as XX′ , XX3′, XX5′ and XX7′ where X is larger size halogen and X′ of smaller size and X is more electropositive than X′. As the ratio between radii of X and X′ increases, the number of atoms per molecule also increases.
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