Ionic Bonds Formed through transfer of electrons betweenatoms of metal and non-metal. Example of metals: sodium, magnesium, iron, lead, aluminium Example of non-metals: Chlorine, sulphur, oxygen Metal atoms donate electrons Non-metals atom accept electronsAchievestablestableelectronelectronarrangementarrangementAchievestablestableelectronelectronarrangementarrangement
Formation of Ionic Bonds Ionic compounds Formed through ionic bonds Example 1: sodium chloride Sodium atom: electron arrangement : 2.8.1 Chlorine atom : electron arrangement : 2.8.7
Formation of ionic bonds of insodium chlorideNa ClNa Cl
Formation of ionic bonds insodium chloride Electron arrangement of sodium atom is 2.8.1 A sodium atom donates one electron to achieve the stable octetelectron arrangement (2.8) Sodium ion, Na+is formed This electron is transferred to a chlorine atom with an electronarrangement of 2.8.7 A chlorine atom accepts electron from sodium atom to achieve thestable octet electron arrangement (2.8.8) Chloride ion, Cl-is formed The sodium ion and chloride ion, formed are attracted to oneanother to form a solid sodium chloride, The strong electrostatic force between the ions is called ionic bond(electrovalent bond)
Formation of Ionic Bonds Example 2: magnesium fluorideMgFFMgF F
Formation of ionic compound magnesium fluoride Electron arrangement of magnesium atom is 2.8.2 A magnesium atom donates two electron to achieve the stableoctet electron arrangement (2.8) Magnesium ion, Mg2+is formed This electron is transferred to two fluorine atom with an electronarrangement of 2.7 two fluorine atom accepts 1 electrons each from magnesium atomto achieve the stable octet electron arrangement (2.8) Fluoride ion, F-is formed The magnesium ion and fluoride ions, formed are attracted to oneanother to form a solid magnesium floride, MgF2. The strong electrostatic force between the ions is called ionic bond(electrovalent bond)
Covalent Bondsnon-metal atomsShare electronsStable electronarrangementSingle bondDoublebondTriplebonda pair of electronsis sharedtwo pairs ofelectrons aresharedthree pairs ofelectrons aresharedFormed by
Single Bond Formed when a pair of electrons is shared between 2 atoms. Example : hydrogen molecule Hydrogen atom has 1 valence electron Needs 1 more to achieve duplet electron arrangement 2 hydrogen atoms contribute one electron each for sharing This shared pair of electrons forms a single bond in hydrogenmolecule, H2
Double Bond 2 pair of electron are sharing between atoms Example: formation of an oxygen molecule, O2 An oxygen atom has 6 valence electron Needs 2 electron to achieve octet electron arrangement 2 oxygen atom each contribute 2 electrons for sharing A double bond is formed between 2 atoms
Triple Bond Is formed when 3 pairs of electron are shared between 2 atoms Example: formation of a nitrogen molecule, N2 Nitrogen atom has the electron arrangement of 2.5. It needs 3 more electron to achieve stable electron arrangement. Each atom contribute 3 electron each Thus sharing 3 pairs of electrons Triple bond is formed between the nitrogen atoms.
Comparison between the ionic bondand covalent bondIonic bond Metal atomsand non-metalatom Transferringelectron Positivelycharged ionand negativelycharged ionCovalent bond Non metalsatoms Sharingelectrons moleculesTypes ofElements involvedin the formationof each bondHow each bondis formedThe particles inthe compoundformed
Try this out!Draw the electron arrangement of the formationfor the following ionic compounds:[Proton number : Li, 3 ; Na, 11 ; K, 19 ; Ca, 20 ;Mg, 12 ; O, 8 ; Cl, 17 ; S, 16] Lithium oxide, Sodium sulphide, Calcium chloride, Magnesium oxide,
Try this out Draw the electron arrangements of theformation Hydrogen chloride Water tetrachloromethane
Try this out Draw the electron arrangements of theformation Carbon dioxide Ammonia (NH3)
The Properties of Ionic andCovalent CompoundsIonic compound Exist as solid High. ->Non-volatile Conduct electricity inaqueoussolution/moltenstate Dissolve in water &do not dissolve inorganic solventsCovalent Compound Exist as solids, liquidor gases Low. ->volatile Do not conductelectricity Dissolve in organicsolvents and do notdissolve in waterPhysical stateat roomtemperatureMelting &boiling pointElectricialconductivitySolubility
Electrical conductivity – ionic compounds Do not conduct electricity in solid. Ions are fixed in positions in the crystal latticestructure Ions do not move freely Conduct electricity in molten or aqueoussolution Ions are free to moveWhy?
Electrical Conductivity – covalent compounds Do not conduct electricity in all states Consist of neutral moleculesWhy?
Melting and Boiling Points Ionic compounds have high melting and boilingpoints. Ions are held together by strong ionic bonds. A lot of energy is needed to overcome the strongelectrostatic forces between the ions Covalent compounds Have low melting and boiling points Consist of molecules that held together by weakintermolecular forces Less heat is required to overcome these forces
Use of covalent compounds Most covalent compounds are good solvents withhigh volatility Example: Alcohol Acetone Ether Hexane Used in Cosmetics Medical industries