{"id":17993,"date":"2023-10-14T17:40:36","date_gmt":"2023-10-14T12:10:36","guid":{"rendered":"https:\/\/wbbsesolutions.guide\/?p=17993"},"modified":"2024-05-23T09:32:56","modified_gmt":"2024-05-23T04:02:56","slug":"covalent-bond-definition-formation-properties-and-types","status":"publish","type":"post","link":"https:\/\/wbbsesolutions.guide\/covalent-bond-definition-formation-properties-and-types\/","title":{"rendered":"WBCHSE Class 11 Chemistry Notes For Covalent Bond – Definition, Formation, Properties and Types"},"content":{"rendered":"
Ionic bonds are formed when one atom loses electrons to achieve a stable configuration and the other atom accepts those electrons to complete the octet in its outermost shell. But what about atoms that have 4 electrons in their valence shell?<\/p>\n
Read and Learn More WBCHSE For Class11 Basic Chemistry Notes<\/a><\/strong><\/p>\n The chlorine molecule<\/strong> Each chlorine atom (Z = 17) has seven electrons in its valence shell (2, 8, 7) and needs one more electron to complete its octet. In the formation of the chlorine molecule, two chlorine atoms contribute one electron each and share two electrons. In this way both the chlorine atoms achieve the stable configuration of eight electrons in their outermost shell. The sharing of electrons by two chlorine atoms or the formation of a bond between them is shown in Figure.<\/p>\n The Ammonia Molecule<\/strong> A nitrogen atom has five electrons in the outermost shell. It shares three of these and attains an octet. Hydrogen has only one electron, it needs one more electron to complete its Is orbital. The nitrogen atom and each of the hydrogen atoms contribute one electron each to the bonded pair. The electron pair left unshared on the nitrogen atom is the lone pair.<\/p>\n The Carbon Tetrachloride Molecule<\/strong> A carbon atom has four valence electrons. It shares all the four electrons with four chlorine atoms to attain an octet in the carbon tetrachloride molecule. Each of the chlorine atoms also attains an octet.<\/p>\n Multiple Covalent Bonds: <\/strong>When two atoms share only one pair of electrons, the bond formed between them is called a single covalent bond. The chlorine, ammonia, and carbon tetrachloride molecules contain single covalent bonds. There is one single covalent bond in a chlorine molecule. The ammonia and carbon tetrachloride molecules contain three and four single covalent bonds respectively.<\/p>\n Now, it is quite possible for two atoms to share more than one pair of electrons. When two atoms share more than one pair of electrons, the bond between the atoms is called a multiple covalent bond. When two atoms share two pairs of electrons, the bond between the atoms is called a double covalent bond and when three pairs of electrons are shared by two atoms, the bond formed between them is called a triple covalent bond.<\/p>\n The Oxygen Molecule<\/strong> The oxygen atom (Z = 8) has six electrons in its valence shell (2,6), so it needs two more electrons to complete its outermost cell. In the formation of the 02 molecule, the two oxygen atoms, therefore, contribute two electrons each and share two pairs of electrons. Thus, in the oxygen molecule, the two oxygen atoms are held by a double bond.<\/p>\n The Nitrogen Molecule<\/strong> The nitrogen atom (Z = 7) has five electrons in its valence shell (2,5) and needs three more electrons to complete its outermost shell. In the nitrogen molecule, therefore, each nitrogen atom contributes three electrons and the two atoms share six electrons, or three electron pairs. Thus, the nitrogen atoms in the N2<\/sub> molecule are held by a triple covalent bond.<\/p>\n The Ethene Molecule<\/strong> An ethene molecule is formed by bonding between two carbon atoms and four hydrogen atoms. Each of the two carbon atoms combines with two hydrogen atoms forming two single covalent bonds (by sharing two of its electrons). The remaining two electrons of each carbon atom form a double bond between e two carbon atoms.<\/p>\n The valency of an element in a covalent compound is known as covalency or the number of electrons which it contributes to form a covalent bond in that compound. For example, the valency of Cl in Cl2<\/sub> is 1, of O in O2<\/sub> is 2. Similarly, the covalency of C in CCl4<\/sub>\u00a0is 4 and that of N in N2<\/sub>\u00a0is 3.<\/p>\n Coordinate Covalent Bond: <\/strong>Certain atoms which have a complete octet and contain a lone pair of electrons can donate this pair to another atom which is short of electrons. When two atoms participate in this kind of sharing of electrons they are said to be bound by a coordinate bond. The coordinate bond can be looked upon as a special type of covalent bond.<\/p>\n Formation of O3<\/sub><\/strong> A molecule of oxygen contains two oxygen atoms which share two pairs of electrons to complete their octets. In the formation of ozone, one of these oxygen atoms donates a pair of electrons to a third oxygen atom, which contains only six electrons.<\/p>\n A combination that contains of only NH3<\/sub> and BF3<\/sub><\/strong> In ammonia, nitrogen has five valence electrons. Three of these are shared with threei hydrogen atoms to form three covalent bonds. Ammonia still has a lone pair of electrons which can be donated to any electron-deficient atom or molecule like BF3<\/sub>.<\/p>\n Formation of SO2<\/sub><\/strong>\u00a0Sulphur and oxygen both have six electrons in their valence shell. Each needs two more electrons to complete its octet, so they share two electrons each, thus forming a double bond with each other.<\/p>\n 1. To find the total number of valence electrons available for bonding in a nitric add (HNO3<\/sub>) molecule, write the valence shell configurations of the combining atoms.<\/p>\n \u21d2 \\(\\mathrm{H}\\left(1 \\mathrm{~s}^1\\right), \\mathrm{N}\\left(2 \\mathrm{~s}^2 2 \\mathrm{p}^3\\right), \\mathrm{O}\\left(2 \\mathrm{~s}^2 2 \\mathrm{p}^4\\right)\\)<\/p>\n The total number of valence electrons is [1 + 5 + 3 x (6)] = 24.<\/p>\n 2. The skeletal structure of HNO3<\/sub>\u00a0is<\/p>\n You can write the above skeletal structure by considering the atomic structure and elemental properties of the combining atoms, which we have already studied in previous classes. Although hydrogen is the least electronegative atom, nitrogen is placed in the centre of the molecule. The valency of nitrogen is 3, whereas that of hydrogen is 1. For the same reason, N is bonded with three oxygen atoms, and the hydrogen atom is bonded to one of the oxygen atoms.<\/p>\n 3. Draw a single bond between each pair of bonding atoms and complete the octets on each oxygen atom.<\/p>\n 4. This does not complete the octet on the nitrogen atom. Therefore, we resort to multiple bonding between one of the oxygen atoms and the nitrogen atom so that each bonded atom gets an octet of electrons.<\/p>\n The carbonate ion \\(\\left(\\mathrm{CO}_3^{2-}\\right))\\)<\/strong><\/p>\n 1. To find the total number of valence electrons available for bonding, write the valence shell configurations of the combining atoms.<\/p>\n \u2234 \\(C\\left(2 s^2 2 p^2\\right) O\\left(2 s^2 2 p^4\\right)\\)<\/p>\n The total number of valence electrons is [4 + 3 x (6)] = 22. The total number of electrons available is 24 since the carbonate anion carries two negative charges.<\/p>\n 2. The skeletal structure of carbonate is<\/p>\n Here carbon is the least electronegative atom and therefore centrally located in the ion.<\/p>\n 3. Draw a single bond between each pair of bonding atoms and complete the octet on each of the oxygen atoms.<\/p>\n 4. In the structure, the octet of carbon is incomplete. Therefore, we resort to multiple bonding between carbon and one of the oxygen atoms.<\/p>\n The octet of each bonded atom is now complete in the structure of the carbonate ion.<\/p>\n Consider the example of the ozone molecule. Its Lewis dot representation is<\/strong><\/p>\n Let us calculate the formal charge on each oxygen atom in the molecule. All the oxygen atoms have six valence electrons. The central oxygen atom marked 1 has one lone pair and three bond pairs.<\/p>\n \u2234 formal charge on oxygen atom marked 1 = 6 – 2- 1\/2 x 6 = +1<\/p>\n The oxygen atom marked 2 has two lone pairs and two bond pairs,<\/p>\n \u2234 formal charge on oxygen atom marked 2 = 6 – 4- 1\/2 x 4 = 0.<\/p>\n The oxygen atom marked 3 has three lone pairs and one bond pair.<\/p>\n \u2234 formal charge on oxygen atom marked 3 = 6 – 6 -1\/2 x 2 = -1<\/p>\n Since O3<\/sub> is a neutral molecule, the sum of the formal charges is zero.<\/p>\n In general, this simple formula can be used to calculate the formal charge (FC) on an atom in a molecule:<\/p>\n FC = (total number of valence electrons in the free atom) – (total number of electrons in the lone pairs) – 1\/2 (total number of shared electrons)<\/p>\n Formal charge is calculated for the species involved in covalent bonding. If there are a number of possible Lewis structures for a molecule, then the values of the formal charges on its atoms help to determine the lowest energy structure. Generally, the structure with the smallest formal charges on the atoms is the one with lowest energy.<\/p>\n Properties of covalent compounds <\/strong>Covalent compounds, or compounds formed by covalent bonding, have the following common characteristics.<\/p>\n State<\/strong> Covalent compounds, unlike ionic compounds, exist as individual molecules in which the atoms are held together by the sharing of electrons. The intermolecular force of attraction in such compounds is generally weak. So most of these compounds exist in the liquid or gaseous state at room temperature.<\/p>\n Melting and boiling points<\/strong> Covalent compounds generally have low melting and boiling points because the inter-molecular force of attraction in such compounds is weak and not much energy is required to overcome this force.<\/p>\n Conductivity<\/strong> They are generally poor conductors of electricity because they do not contain free electrons or ions to conduct electricity.<\/p>\n Solubility<\/strong> They are usually insoluble in water because of the lack of interaction between the polar molecules of water and the nonpolar molecules of such compounds. But they dissolve in nonpolar solvents like benzene.<\/p>\n Molecular reactions<\/strong> Covalent compounds do not produce ions when dissolved. So, when such compounds react with other reagents, the reaction does not involve the combination of ions. It involves the cleavage of the covalent bond in the reacting species and the formation of new covalent bonds in the product molecules. Such reactions are naturally much slower than ionic reactions.<\/p>\n","protected":false},"excerpt":{"rendered":" Covalent Bond Ionic bonds are formed when one atom loses electrons to achieve a stable configuration and the other atom accepts those electrons to complete the octet in its outermost shell. But what about atoms that have 4 electrons in their valence shell? It would be difficult for such an atom to either lose or … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[47],"tags":[],"yoast_head":"\n<\/p>\n
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The Nitric Acid Molecule<\/h2>\n
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