Chemical Bonds
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Transcript of Chemical Bonds
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Chemical Bond
• The interaction b/ atoms/ions that results in a decrease in potential energy of the system which hence becomes stable.
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Electron -dot(Lewis) symbols
Valence electrons are shown as dots around the symbols of the atoms.
1 2 13 14 15 16 17 18
H He:
Li Be B C N O : F :Ne :
Na Mg Al Si P S :Cl :Ar :
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Types of bonds
• Ionic
• Covalent
• Metallic
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IONIC BONDThe Electrostatic
attraction forces happen b/ metal and nonmetal
ions as a results of exchanging electrons.
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Ionic Bonds: One Big Greedy Thief Dog!
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-have crystalline structure formed of repeating units).
-ions stay together as a result of attraction b/ oppositely charged ions.
-The 3D structure of the crystalline is named as :lattice.”
Properties of ionic compounds
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• Hard, brittle.
• Relatively high melting and boiling points
• Do not conduct the electricity when solid but do when molten or in aqueous solution (since the ions are free to move).
• Are more soluble in water than other solvents
Properties of ionic compounds
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Ex.
• Write
a)Lewis (electron-dot) formula
b)Chemical formula
of the compound formed b/ Mg and O.
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Ex.
• Write
a)Lewis (electron-dot) formula
b)Chemical formula
of the compound formed b/ Al and S.
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NAMING IONIC COMPUNDS (P.100)
• Name of the metal+ ionic name of the nonmetal
Name of the metal+ name of the polyatomic ion
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NAMING IONIC COMPUNDS (P.100)
Name of the metal (oxidation state of the metal in Roman numeral) + ionic name of the nonmetal
Name of the metal (oxidation state of the metal in Roman numeral) + name of the polyatomic ion
Compounds Made with Variable Charged Metals
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NAMING IONIC COMPOUNDS
• NaBr
• FeCl2
• Mg3N2
• Al4C3
• CuO
• LiH
• K3P
• PbO2
• CuS
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NAMING IONIC COMPOUNDS
• BaCO3
• Zn(NO3)2
• Rb3(PO4)
• Fe(OH)3
• AgHCO3 CoI2
• CaSO4 NiCr2O7
• CuOH CrCrO4
• MnO2 KMnO4
• K2C2O4 Sr(ClO4)2
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COVALENT BOND:Happens b/ nonmetal atoms as a result of sharing electrons.
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• Many interactions are present:
– The attraction forces b/ the electrons and nucleus
– Repulsion forces b/ the electrons
– Repulsion forces b/ the nuclei
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The shared electrons are attracted w/ an equal power
by both atoms in the bonding.
NONPOLAR COVALENT BOND:
H2 , Cl2,Br2,Cl2,O2,N2
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Oxygen AtomOxygen Atom Oxygen AtomOxygen Atom
Oxygen Molecule (O2)
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H2,Cl2:
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The shared electrons are NOT attracted w/ an equal power by
the atoms in the bonding.
POLAR COVALENT BOND:
H2O,HF, HCl,NH3,CH4
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• The sharing of electrons in HF is unequal: the fluorine atom attracts electron density away from the hydrogen (the bond is thus a polar covalent bond)
• The H-F bond can thus be represented as:
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Electronegativity and bond polarity
The ‘ δ+' and ' δ -' symbols indicate partial positive and negative charges.The arrow indicates the "pull" of electrons off the hydrogen and towards the more electronegative atom
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The bond gets polar as the difference in the electronegativities of the atoms bonded increases.
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HCl:
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Bond energy• bond energy (E) is the measure of bond strength in
a chemical bond. It is the heat required to break one mole of gaseous molecules into their individual gaseous atoms.
33(Bond energy)
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Bond energy
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• Strong interactions have greater bond energies than that of the weak interactions.
Ar(s) + 6.4 kJ Ar(g)
H2O(s) + 43.9 kJ H2O(g)
H2O(g) + 463.4 kJ 2H•(g) + OH•(g)
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Bond energy
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Bond length Bond energy
C
C
C
C
CC
154 pm
134 pm
120 pm 835 kJ/mol
602 kJ/mol
346 kJ/mol
Bond length:The average distance b/ the nuclei of the atoms when the attraction and repulsion forces b/ the atoms are balanced.
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Bond length: C-C > C=C > C≡C
Bond energy: C-C < C=C < C≡C
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Dublet(duet) Rule: Completion of valence electron number to 2 when atoms make bonds in order to reach the stability of He (H,Li).
Octet Rule: Completion ve number to 8 when the atoms make a bond in order to reach the stability of Noble gases. (O,N,F,C,Cl,Br,I,P,S…)
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Atoms that are out of duet and octet rules:
Be,B
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Naming covalent compounds
• (prefix to indicate the number of 1st nonmetal+name of 1st nonmetal) + (prefix to indicate the number of 2nd nonmetal+ ionic name of second nonmetal)
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Naming covalent compounds
• For you own information, here is some other generally useful information:
• Roman Numerals
• I = 1; II = 2; III = 3; IV = 4; V = 5; VI = 6; VII = 7.
• Prefixes:
• mono = 1; di = 2; tri = 3; tetra = 4; penta = 5; hexa = 6; hepta = 7; octa = 8.
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Naming covalent compounds
• N2O3
• N2 O5
• Cl3F
• Cl2O7
• Cl2O
• PCl3
• SF4
• P2S3
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Naming compounds including polyatomic ions only
• Name of 1st polyatomic ion + Name of 2nd polyatomic ion
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Naming covalent compounds
• (NH4)3PO4
• (NH4)2SO4
• (NH4)2S
• NH4Cl
• (NH4)2CO3
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Bond Bond formationformation
Bond Bond formationformation
ClH H Cl••
••
••
••
••
••
+
Notice that each atom has one Notice that each atom has one unpaired electronunpaired electron!!!!!!!!!!
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Cov. Bond and lone (non-Cov. Bond and lone (non-bonding) electronsbonding) electrons::
Cov. Bond and lone (non-Cov. Bond and lone (non-bonding) electronsbonding) electrons::
•
••
•
••
H ClLone pair electrons
Bonding electrons
LEWIS LEWIS formformula!!!ula!!!
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HCl
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WARNING!!!!!!!!!!!!
All diatomic molecules have a linear geometry…