Bonding

Chemical Bonds Chemical Bonds result from simultaneous attraction of electrons to TWO or more nuclei TWO conditions for stability of atoms in relation to bonding –Full Valence(complete outer shell) –Electrical Neutrality

Electrons are placed in shells according to rules: 1)The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons. Chemical bonds: an attempt to fill electron shells

Bonds Between Atoms Electrons may be transferred or shared between atoms –Ionic compounds are formed when electrons are transferred (lost or gained) between atoms –Covalent molecules are formed when electrons are shared (equally or unequally) between atoms

Ionization Energy The amount of energy needed to remove the most loosely bound electron from a neutral atom in the gaseous phase

The tendency to lose electrons is evidence of metallic character –Metals tend to lose electrons when interacting –Metals gain a positive charge as ions when bonding

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons

IONIC BOND bond formed between two atoms by the transfer of electrons

Ionic compounds result when metals react with nonmetals Electrostatic Force (+ and -) holds ions together

Formation of Sodium Ion Sodium atom Sodium ion Na  – e   Na p + 11 p + 11 e - 10 e

Formation of Magnesium Ion Magnesium atom Magnesium ion  Mg  – 2e   Mg p + 12 p + 12 e- 10 e

Ions from Nonmetals In ionic compounds, nonmetals in 15, 16, and 17 gain electrons from metals Nonmetal add electrons to achieve the octet arrangement Nonmetal ionic charge: 3-, 2-, or 1-

Fluoride Ion unpaired electronoctet     1 - : F  + e  : F :     p+ 9 p + 9 e- 10 e ionic charge

COVALENT BOND bond formed by the sharing of electrons

Covalent Bond Bonding between two or more nonmetals

Bonds in all the polyatomic ions and diatomics are all covalent bonds -Polyatomic ions: ions containing two or more elements (found on the back of PT) -Diatomics: elements that are always found in pairs, two bonded together (N 2, O 2, F 2, Cl 2, Br 2, I 2, H 2 )

when electrons are shared equally between atoms NONPOLAR COVALENT BONDS H 2 or Cl 2

when electrons are shared but shared unequally between atoms POLAR COVALENT BONDS H2OH2O

- water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

METALLIC BOND bond found in metals; holds metal atoms together very strongly

Metallic Bonding Metals lose electrons and cannot normally accept them. The electrons are given up to a “sea" of electrons that surrounds the metal atoms. The electrons become the property of ALL the atoms.

Metallic Bond Formed between atoms of metallic elements Electron cloud around atoms properties of metals… malleable, ductile, good conductors of electricity, high luster, hardness.