The bond between two atoms formed by sharing of two pairs of electrons is called a double bond. Two horizontal lines between two atoms denote a double bond, e.g., O = O(O2)
(i) Formation of oxygen molecule, O2: Oxygen atom has six electrons in its outermost shell, two short of forming a complete octet. Thus each oxygen atom in O2 shares 2 electrons with the other oxygen atom and attains stable configuration as shown:
(ii) Formation of ethylene molecule (C2H4): In ethylene two carbon atoms share two pairs of electrons between them and the rest two electrons on each carbon atom share one electron each with two hydrogen atoms. Thus ethylene molecule has one double bond (C = C) and four single bonds (C—H).
D.
100% pure ethanoic acid.The covalent bond is said to be formed when two atoms achieve stability by sharing of an electron pair, each contributing one electron to the electron-pair. In this way, the atoms can be regarded as having acquired a noble gas configuration.
e.g.,
The bond formed between two atoms through the sharing of three electron pairs is called a triple bond. Three horizontal lines between two atoms denote a triple bond, e.g., nitrogen molecule is given asN≡N.
(i) Formation of N2 molecule: Nitrogen atoms have five electrons in their outermost shells. Therefore, in N2 molecules, two nitrogen atoms share 3 electrons with each other, thus acquiring the stable structure and forming a N2 molecule with triple bonds.
(ii) Formation of acetylene molecule (C2H2): In acetylene molecule, each carbon atom satisfies its valency by sharing one electron with a hydrogen atom and sharing the other three electrons with the other carbon atom as shown: