Ionic Compounds Chapter 5. What are ions? ► An ion is an atom or group of atom that has an electric charge because it has gained or lost electron. ► [Na]=

Ionic CompoundsIonic Compounds

Chapter 5Chapter 5

What are ions?What are ions?

►An ion is an atom or group of atom that An ion is an atom or group of atom that has an electric charge because it has has an electric charge because it has gained or lost electron.gained or lost electron.

►[Na]= 1s[Na]= 1s2 2 2s2s² 2p² 2p6 6 3s3s11

► [Na[Na++] = ] = 1s1s2 2 2s2s² 2p² 2p6 6

►When a sodium atom loses its When a sodium atom loses its outermost electron, it becomes outermost electron, it becomes positively charged ion called as sodium positively charged ion called as sodium ion.ion.

Cations and anionsCations and anions

► Ions with a positive charge are called Ions with a positive charge are called as cations. They have more protons as cations. They have more protons than electrons.than electrons.

►Negatively charged ions are called as Negatively charged ions are called as anions. They have more electrons than anions. They have more electrons than protons.protons.

► [Cl[Cl--] = 1s] = 1s²2s²2p²2s²2p663s²3p3s²3p6 6 =[Ar]=[Ar]► [Cl] = [Cl] = 1s1s²2s²2p²2s²2p663s²3p3s²3p55

► Collection of cations are never found without Collection of cations are never found without the formation of similar number of anions. the formation of similar number of anions. The concept of having equal number of The concept of having equal number of positive charges is called electroneutrality.positive charges is called electroneutrality.

Class PracticeClass Practice

►What will be the electronic What will be the electronic configuration of configuration of

►[Ca] and [Ca[Ca] and [Ca2+2+]]

Write down the number of protons and Write down the number of protons and electrons.electrons.

Transition metalsTransition metals

►Not all simple ions are isoelectronic Not all simple ions are isoelectronic with noble gas atoms. The transition with noble gas atoms. The transition metals do not fit this pattern. metals do not fit this pattern. Lanthanides and actinides elements Lanthanides and actinides elements form cations, mostly with +3 charges, form cations, mostly with +3 charges, hence they are not isoelectronic with hence they are not isoelectronic with noble gases.noble gases.

Octet ruleOctet rule

►The tendency of atoms of elements to The tendency of atoms of elements to gain or lose electrons so that their gain or lose electrons so that their outer s and p orbitals are full with outer s and p orbitals are full with eight electrons.eight electrons.

The tendency of atoms to match the The tendency of atoms to match the electron configuration of the s and p electron configuration of the s and p orbitals of a noble gas is called the orbitals of a noble gas is called the octet rule.octet rule.

Binary ionic compoundBinary ionic compound

►An ionic compound composed of An ionic compound composed of simple cation and simple anion is simple cation and simple anion is called a binary ionic compound.called a binary ionic compound.

►Common table salt NaCl is composed Common table salt NaCl is composed of equal number of sodium ions, Naof equal number of sodium ions, Na+ +

and chloride ions Cland chloride ions Cl--..

Naming Binary CompoundsNaming Binary Compounds

► The name consists of two words: the name The name consists of two words: the name of the cation followed by the name of the of the cation followed by the name of the anion.anion.

►NaCl sodium chlorideNaCl sodium chloride►MgMg33NN2 2 magnesium nitridemagnesium nitride

► The magnesium ion,MgThe magnesium ion,Mg2+ 2+ has two positive has two positive charges, and the nitride ion, Ncharges, and the nitride ion, N3- 3- has three has three negative charges. We must combine in such negative charges. We must combine in such a way that there are as many negative a way that there are as many negative charges as there are positive charges.charges as there are positive charges.

►Three MgThree Mg2+2+ cations are needed for cations are needed for every two Nevery two N3- 3- anions to produce anions to produce electrically neutral compounds. electrically neutral compounds. Subscripts denote 3 magnesium ions Subscripts denote 3 magnesium ions and 2 nitride ions.and 2 nitride ions.

Home workHome work

►Page 164 Section reviewPage 164 Section review►Q1) b and c.Q1) b and c.►Q2) a, d, e and h.Q2) a, d, e and h.►Q3) e, c and d.Q3) e, c and d.

Ionic BondingIonic Bonding

►Sodium a very reactive Group I metal Sodium a very reactive Group I metal combines with chlorine a reactive combines with chlorine a reactive Group 17 non metal ( a poisonous Group 17 non metal ( a poisonous yellowish green gas that consists of yellowish green gas that consists of molecules with two chlorine atoms molecules with two chlorine atoms bonded together) react a violent bonded together) react a violent exothermic reaction occurs. The white exothermic reaction occurs. The white residue formed from two dangerous residue formed from two dangerous elements is the salt we eat every day.elements is the salt we eat every day.

Crystal structure of NaClCrystal structure of NaCl

►The coulombic force of attraction of The coulombic force of attraction of oppositely charged ions is greater than oppositely charged ions is greater than the coulombic force of repulsion from the coulombic force of repulsion from the ions of like charges. Coulombic the ions of like charges. Coulombic force is the attraction or repulsion force is the attraction or repulsion between two objects that have electric between two objects that have electric charges.charges.

Energy aspects of salt Energy aspects of salt formation.formation.

► Ionization energy is the energy that Ionization energy is the energy that must be supplied to remove the must be supplied to remove the outermost electron from an atom. outermost electron from an atom. Atoms always resist having their Atoms always resist having their electrons removed so their ionization electrons removed so their ionization energies are always positive.energies are always positive.

►NaNa(g) (g) +495 kJ/mol --+495 kJ/mol -- Na Na++(g) (g) +e+e-- (g)(g)

►Electron affinity is the energy needed to Electron affinity is the energy needed to put an extra electron into a neutral put an extra electron into a neutral atom. Most electron affinities are atom. Most electron affinities are negative indicating that the recipient negative indicating that the recipient atom easily accepts another electron.atom easily accepts another electron.

►ClCl(g) (g) +e+e--(g) (g) -349 kJ/mol ---349 kJ/mol -- Cl Cl--(g)(g)

►Adding the above two equations we find Adding the above two equations we find that the electron transfer from sodium that the electron transfer from sodium to chlorine atom is an endothermic to chlorine atom is an endothermic reaction.reaction.

►NaNa(g) (g) +Cl+Cl(g) (g) +146 kJ/mol --+146 kJ/mol -- Na Na++(g) (g) + Cl+ Cl--(g)(g)

► This is very different from what happens in This is very different from what happens in the flask. The formation if ions is only a part the flask. The formation if ions is only a part of the reation.of the reation.

► 1. The energy must be added to convert 1 1. The energy must be added to convert 1 mol of sodium from a solid to a gas.mol of sodium from a solid to a gas.

NaNa(s) (s) + energy --+ energy -- Na Na(g)(g)

2. More energy must be added to remove 2. More energy must be added to remove one electron from each sodium atom.one electron from each sodium atom.

NaNa(g) (g) +energy --+energy -- Na Na+ + (g) (g) +e-+e-

► 3. No energy is needed to convert chlorine into gaseous 3. No energy is needed to convert chlorine into gaseous state because it is already a gas. However energy must be state because it is already a gas. However energy must be added to break up added to break up ½ mole of Cl½ mole of Cl2 2 molecules to produce 1 molecules to produce 1 mol of chlorine atoms.mol of chlorine atoms.½Cl½Cl2(g) 2(g) + energy ---+ energy --- Cl Cl(g)(g)

► 4. Some energy is given off when an electron is 4. Some energy is given off when an electron is added to each chlorine atom to form Cladded to each chlorine atom to form Cl - - ion. This is an ion. This is an exothermic reaction.exothermic reaction.ClCl(g) (g) + e+ e- - ---- Cl Cl- - (g) (g) + energy+ energy

► 5. Much more energy is given off when Na5. Much more energy is given off when Na+ + and Cland Cl- - ions ions come together to form ionic crystal of NaCl.come together to form ionic crystal of NaCl.Na Na ++

(g) (g) + Cl+ Cl- - (g) (g) ---- NaCl NaCl (s) (s) +energy.+energy.

Properties Of Binary ionic Properties Of Binary ionic compoundscompounds

►A simple cation combined with a simple A simple cation combined with a simple anion results in binary compounds.anion results in binary compounds.

►Since they form strong ionic bonds they Since they form strong ionic bonds they have higher melting and boiling points.have higher melting and boiling points.

►Since they have strong ionic bond these Since they have strong ionic bond these solids are not good conductors of solids are not good conductors of electricity.electricity.

►However in solution they form ions However in solution they form ions which help in conducting electricity.which help in conducting electricity.

Polyatomic ionsPolyatomic ions

►An electrically charged group of two or An electrically charged group of two or more chemically bonded atoms that more chemically bonded atoms that functions as a single ion. functions as a single ion.

Charges of poly atomic ions.Charges of poly atomic ions.

Oxidation numbersOxidation numbers

► A number assigned to an atom in a A number assigned to an atom in a polyatomic ion or molecular compound polyatomic ion or molecular compound based on complete transfer of electrons.based on complete transfer of electrons.

► Some guide lines:Some guide lines:► 1. The oxidation number of any free or 1. The oxidation number of any free or

combined element is zero.combined element is zero.► 2. Oxidation number for mono atomic ion is 2. Oxidation number for mono atomic ion is

the charge on the ion.the charge on the ion.► 3.The oxidation number on hydrogen is +1 3.The oxidation number on hydrogen is +1

unless combined with a metal when it has a unless combined with a metal when it has a charge -1.charge -1.

► The oxidation number of halogen is -1 since The oxidation number of halogen is -1 since more electro negative.more electro negative.

►Oxygen has an oxidation number -2 except Oxygen has an oxidation number -2 except in peroxides it is -1 and when combined with in peroxides it is -1 and when combined with fluorine it is +2.fluorine it is +2.

► In compounds the metals in Group I,II and Al In compounds the metals in Group I,II and Al have oxidation numbers +1,+2 and +3.have oxidation numbers +1,+2 and +3.

► The sum of the oxidation number for all the The sum of the oxidation number for all the atoms in a compound is zero.atoms in a compound is zero.

► The sum of the oxidation number for all The sum of the oxidation number for all polyatomic ion is equal to the charge on that polyatomic ion is equal to the charge on that ion.ion.

HomeworkHomework

►Page 181Page 181►# 1-5# 1-5

Silicates and HydratesSilicates and Hydrates

Silicates are any compounds Silicates are any compounds containing silicon, oxygen, one or containing silicon, oxygen, one or more metals, and possibly hydrogenmore metals, and possibly hydrogen

► Ionic compounds like copper sulfate Ionic compounds like copper sulfate CuSOCuSO44 with water molecules with water molecules incorporated into their crystal lattices incorporated into their crystal lattices are called hydrates. Some salts form are called hydrates. Some salts form hydrates. E.g CuSOhydrates. E.g CuSO44.5H.5H22OO

►When a hydrated compound is heated When a hydrated compound is heated to get rid of the water molecule the to get rid of the water molecule the remaining salt is anhydrous.remaining salt is anhydrous.

HomeworkHomework

►Page 184 Page 184 ►Q.3 a, c, e, f, i ,jQ.3 a, c, e, f, i ,j►Q.4 allQ.4 all►Q.5. a, c, d, e, h.Q.5. a, c, d, e, h.

Class work Class work

►Test prep page 191.Test prep page 191.