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VII Atomic Structure C. Bonding. Bonding. Bonding between atoms in a compound comes from the sharing of electrons The kind of bond formed between the two atoms depends on the amount of sharing of the electrons. Bonding in Compounds. Kinds of Bonds Ionic - PowerPoint PPT Presentation
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VII Atomic Structure C
Bonding
Bonding
• Bonding between atoms in a compound comes from the sharing of electrons
• The kind of bond formed between the two atoms depends on the amount of sharing of the electrons
Bonding in Compounds
• Kinds of Bonds
Ionic
electron transferred from one atom to another
generally between a metal cation and a non metal anion
Covalent
electrons shared between 2 atoms in a bond
• Electronegativity– Measure of the ability of an atom in a bond
to attract the bonding electrons– Across a Period: EN increases– Down a Group: EN decreases– Most electronegative element is fluorine
Li Be B C N O F1.0 1.5 2.0 2.5 3.0 3.5 4.0Na Mg Al Si P S Cl0.9 1.2 1.5 1.8 2.1 2.5 3.0K Ca Ga Ge As Se Br0.8 1.0 1.6 1.8 2.0 2.4 2.8
Determine the amount of covalent or ionic character in a bond
Using Electronegativity
• The difference in electronegativity between two atoms can be used to determine how ionic or how covalent the bond is
Difference in electronegativityEN
EN = 1.7 = 50% ionic
EN > 1.7 more ionic
EN < 1.7 more covalent
The larger the EN, the more ionic the bond
The smaller the EN, the more covalent the bond
So the farther apart the atoms are the more ionic the bond
Compare three bonds:
A) C--F B) O--F C) N--F
Which is the most ionic?
Compare three bonds:
A) C--F B) O--F C) N--F
Which is the most covalent?
1. The bond with the smaller cation is the more covalent bond
2. The bond with the larger anion is the more covalent bond
3. The bond with the larger charge on the cation or anion is the more covalent bond
4. The bond with a transition metal cation is the more covalent bond
•Determine the amount of covalent or ionic character in a bond
•Fajan’s Rules of Covalency
• Predict which is the more covalent
A) SbCl3B) BiCl3
C) BeOD) BeS
E) Tl2O
F) Tl2O3
G) NaClH) CuCl
Sb is smaller than Bi, so the SbCl3 ismore covalent
S is larger than O, so the BeS is more covalent
Compare Tl+ and Tl+3 , thallium(III) oxidemore covalent
Cu is a transition metal, CuCl more covalent
Which is the Most Covalent?
A) MgCl2B) MgBr2
C) CaCl2D) CaBr2
Which is the Most Covalent?
A) MgCl2B) MgBr2
C) CaCl2D) CaBr2
Compare: Mg cation and Ca cation.Mg smaller than Ca so Mg compounds more covalent
Compare: Cl anion and Br anion.Br larger than Cl, so Br compounds more covalent
Which is the Most Ionic?
A) MgCl2B) MgBr2
C) CaCl2D) CaBr2
Which is the Most Ionic?
A) MgCl2B) MgBr2
C) CaCl2D) CaBr2
Most ionic is the same as least covalent
Compare: Mg cation and Ca cation.Mg smaller than Ca so Mg compounds more covalent, Ca more ionic
Compare: Cl anion and Br anion.Br larger than Cl, so Br compounds more covalent, Cl more ionic
Which of the following is least covalent?
A) Cu2O
B) CuO
C) Cu2S
D) CuS
Which of the following is least covalent?
A) Cu2O
B) CuO
C) Cu2S
D) CuSCompare anions O and S. S is the larger anion, so it forms more covalent bonds. Therefore, Cu2O and CuO are less covalent
Cu2O is Cu+1, CuO is Cu+2 , the larger charge is more covalent, so Cu2O is the least covalent
Which of the following is least ionic?
A) AgCl
B) NaCl
C) AuCl
D) RbCl
Which of the following is least ionic?
A) AgCl
B) NaCl
C) AuCl
D) RbCl
Least ionic is Most covalent
Ag and Au are transition metals, so they are more covalent than Na and Rb which are Group 1 Alkali metals.
Compare Ag and Au. Ag is the smaller size so it forms the most covalent bond.
• Bond polarity– Because electrons are shared unequally in
a bond due to the difference in electronegativity, a covalent bond has a positive end and a negative end. (poles)
– The bond is said to be polar
H ---Cl– Bond dipole - occurs when you have a
polar bond– Dipole moment () - is a measure of the
bond dipole (the amount of polarity)
+ -
• Bond Polarity– The more ionic the bond the more polar the
bond– The more ionic the bond, the larger the bond
dipole– The more ionic the bond, the greater the dipole
moment.
Compare three bonds:
A) C--F B) O--F C) N--F
Which is the least polar bond?