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1 Chapter-2 CHEMICAL BONDING Chemical bonding: The force by which two (or more) atoms are held together to form a stable molecule. Chemical bond Why do atoms participate in chemical bonding ? Reason: The elements with unstable electronic configuration participate in chemical bonding to attain stable electronic configuration. How do the atoms form chemical bonds and attain stable electronic configuration? Ans: The atoms having unstable electronic configuration lose or gain electrons or share electrons with other atoms to attain stability. What is stable electronic configuration? If an element has 8 electrons in its valence shell (outer most orbit) or completely filled valence shell then it is said to have stable electronic configuration. e.g : Noble gases posses stable electronic configuration. Noble gas Electronic configuratio n K L M N Helium 2 Neon 2 8 Argon 2 8 8 Krypton 2 8 18 8 Since the noble gases have stable electronic configuration they do not participate in chemical bonding hence they are inert. Helium has duplet configuration i.e. 2 electrons in valence shell Noble gases other than Helium have octet configuration i.e. 8 valence electrons. The elements with unstable electronic configuration tend to attain the stable electronic configuration of the nearest noble gas by either electron transfer or sharing electrons - Octet rule Stable electronic configuration (stability) is attained by an in the following ways: i) By electron transfer between two atoms- Electrovalent bond ii) By the mutual sharing of electrons between the atoms- Covalent bond Electrovalent bond (or) Ionic bond: The transfer of electron/s between the atoms with a higher difference in their electronegativity values leads to the formation of Electrovalent bond. ICSE CHEMISTRY for Class X www.icsechemistry16.blogspot.com http://icsechemistry16.blogspot.com
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