Chemical Bonds
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Transcript of Chemical Bonds
Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons
C would like to N would like toO would like to
Gain 4 electronsGain 3 electronsGain 2 electrons
Electron Dot Structures
Symbols of atoms with dots to represent the valence-shell electrons
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 :
Chemical bond
• A chemical bond forms when outer-shell electrons of different atoms come close enough to each other to interact and rearrange themselves into a more stable arrangement.
Types of Chemical Bonds
• Ionic bonds formed when metal atoms combined with non-metal atoms
• Metallic bonds formed when metal atoms combined with metal atoms.
• Covalent bonds formed when non-metal atoms combined with non-metal atoms.
Ionic Compounds
1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.
How many chlorine ions surround each sodium ion and vice versa?
NaCl coordination number- 6:6
The coordination number of an ionic lattice is writtenas a ratio x:y
Hardness and Brittleness
Figure 6.4 Figure 6.4 The repulsion The repulsion between like charges between like charges causes this sodium causes this sodium chloride crystal to chloride crystal to shatter when it is hit shatter when it is hit sharply.sharply.
Electrical Conductivity
• In the solid form, ions in sodium chloride are held in the crystal lattice and are not free to move so cannot conduct electricity.
• When the solid melts the ions are free to move. • In a similar way, when sodium chloride dissolves
in water, the ions separate and are free to move towards the opposite charge.
Properties of Ionic Compounds
– Forms crystal composed of 3d array of ions (ionic network lattice)
– Have high melting and boiling temperatures.
– Are hard but brittle
– Do NOT conduct electricity in the solid state
– They will only conduct electricity if they are melted or dissolved in water.
Structure
• From the properties we can conclude:– The forces between the particles are strong.– There are no free-moving electrons present,
unlike in metals.– There are charged particles present, but in solid
state they are not free to move. – When an ionic compound melts, however, the
particles are free to move and the compound will conduct electricity.
Use Electron shell diagram and simple equation to show the formation of:
• NaCl
• MgO
Naming Binary Ionic CompoundsContain 2 different elements
Name the metal first, then the nonmetal as -ide.
Examples:
NaCl sodium chloride
ZnI2 zinc iodide
Al2O3 aluminum oxide
Practise
Complete the names of the following binary compounds:
Na3N ________________
KBr ________________
Al2O3 ________________
MgS _________________________
Solution
Complete the names of the following binary compounds:
Na3N sodium nitride
KBr potassium bromide
Al2O3 aluminum oxide
MgS magnesium sulfide
Transition Metals
Many form 2 or more positive ions
1+ 2+ 1+ or 2+ 2+ or 3+
Ag+ Cd2+ Cu+, Cu2+ Fe2+, Fe3+
silver cadmium copper(I) ion iron(II) ion
ion ion copper (II) ion iron(III) ion
Zn2+
zinc ion
Write symbols for these:• Potassium ion
• Magnesium ion
• Copper (II) ion
• Chromium (VI) ion
• Barium ion
• Mercury (II) ion
Formula of ionic compounds
Criss-Cross MethodCriss-Cross Method
1.1. Write the symbols for the ions side by side. Write Write the symbols for the ions side by side. Write the cation first.the cation first.• AlAl3+3+ OO2-2-
1.1. Write the symbols for the ions side by side. Write Write the symbols for the ions side by side. Write the cation first.the cation first.• AlAl3+3+ OO2-2-
2.2. Cross over the charges by using the absolute value Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other of each ion’s charge as the subscript for the other ion.ion.• AlAl22 OO33
3. Check the subscripts and divide them by their 3. Check the subscripts and divide them by their largest common factor to give the smallest possible largest common factor to give the smallest possible whole-number ratio of ions. Then write the whole-number ratio of ions. Then write the formula.formula.• AlAl22OO33
• For Al: 2 x 3For Al: 2 x 3++ = 6 = 6++ For O: 3 x 2For O: 3 x 2-- = 6 = 6--
2.2. Cross over the charges by using the absolute value Cross over the charges by using the absolute value of each ion’s charge as the subscript for the other of each ion’s charge as the subscript for the other ion.ion.• AlAl22 OO33
3. Check the subscripts and divide them by their 3. Check the subscripts and divide them by their largest common factor to give the smallest possible largest common factor to give the smallest possible whole-number ratio of ions. Then write the whole-number ratio of ions. Then write the formula.formula.• AlAl22OO33
• For Al: 2 x 3For Al: 2 x 3++ = 6 = 6++ For O: 3 x 2For O: 3 x 2-- = 6 = 6--
Example 1: Calcium and OxygenExample 1: Calcium and Oxygen
Calcium Ca2+ Ca2+
Oxide O2-
O2-
Ca2O2
Criss-Cross Method
CaO
Example 2: Magnesium and PhosphorusExample 2: Magnesium and Phosphorus
Magnesium
Mg2
+
Mg2
+
Phosphorus
P3-
P3-
Mg3P
2
Criss-Cross Method
The sum of the cation charge and the sum of the anion charge The sum of the cation charge and the sum of the anion charge must cancel each other so that the compound formed is must cancel each other so that the compound formed is neutral.neutral.
Practise
1. The formula for the ionic compound of
Na+ and O2- is
1) NaO 2) Na2O 3) NaO2
2. The formula of a compound of aluminum and chlorine is
1) Al3Cl 2) AlCl2 3) AlCl3
3. The formula of Fe3+ and O2- is
1) Fe3O2 2) FeO3 3) Fe2O3
Solution
A. The formula for the ionic compound of Na+ and O2- is
2) Na2O
B. The formula of a compound of aluminum and chlorine is
3) AlCl3
C. The formula of Fe3+ and O2- is
3) Fe2O3
Sample Problem 7-1
•Write the formulas for the binary ionic compounds Write the formulas for the binary ionic compounds formed between the following elements:formed between the following elements:
A. lithium and fluorineB. lithium and oxygen
Names of Variable Ions
Use a roman number after the name of a metal that forms two or more ions
Transition metals and the metals in groups 4A and 5A
FeCl3 (Fe3+) iron (III) chloride
CuCl (Cu+ ) copper (I) chloride
SnF4 (Sn4+) tin (IV) fluoride
PbCl2 (Pb2+) lead (II) chloride
Fe2S3 (Fe3+) iron (III) sulfide
II. Stock system (roman numerals)
Example:Example:
Fe2+
• Iron(II)Iron(II)
Fe3+
• Iron(III)Iron(III)
CuCl• copper(I) chloridecopper(I) chloride
CuCl2• copper(II) chloridecopper(II) chloride
Sample Problem 7-2
a. Write the formula and give the name for the a. Write the formula and give the name for the compound formed from the ions Crcompound formed from the ions Cr3+3+ and F and F--..
b. Write the name for Cub. Write the name for Cu33NN22..
Fe [Ar] 3d64s2
Fe2+ [Ar] 3d6
Fe3+ [Ar] 3d5
Here are the changes in the electronic structure of iron to make the 2+ or the 3+ ion.
Learning Check
Complete the names of the following binary
compounds with variable metal ions:
FeBr2 iron (_____) bromide
Cu2O copper (_____) oxide
SnCl4 ___(_____ ) ______________
Fe2O3 ________________________
CuS ________________________
Solution
Complete the names of the following binary
compounds with variable metal ions:
FeBr2 iron ( II ) bromide
Cu2O copper ( I ) oxide
SnCl4 tin (IV) chloride
Fe2O3 iron (III) oxide
CuS copper (II) sulfide
Learning Check
Name the following compounds:A. CaO
1) calcium oxide 2) calcium(I) oxide3) calcium (II) oxide
B. SnCl4 1) tin tetrachloride 2) tin(II) chloride 3) tin(IV) chloride
C. Co2O3
1) cobalt oxide 2) cobalt (III) oxide3) cobalt trioxide
Solution
Name the following compounds:
A. CaO 1) calcium oxide
B. SnCl4 3) tin(IV) chloride
C. Co2O3 2) cobalt (III) oxide
Learning Check
Write the correct formula for the compounds containing the following ions:
A. Na+, S2-
1) NaS 2) Na2S 3) NaS2
B. Al3+, Cl-
1) AlCl3 2) AlCl 3) Al3Cl
C. Mg2+, N3-
1) MgN 2) Mg2N3 3) Mg3N2
Solution
A. Na+, S2-
2) Na2S
B. Al3+, Cl-
1) AlCl3
C. Mg2+, N3-
3) Mg3N2
Practise
Na2O K2S MgBr2 AlN Ba3As2
CaCl2 AgCl AlH3 ZnI2 Li3P
Name the following ionic compounds:
Nomenclature of binary ionic compounds
Na2O = sodium oxide K2S = potassium sulfide
MgBr2 = magnesium bromide AlN = aluminum nitride
Ba3As2 = barium arsenide CaCl2 = calcium chloride
AgCl = silver chloride AlH3 = aluminum hydride ZnI2 = zinc iodide Li3P = lithium phosphide
Answers:
III. Polyatomic Ions
A A chargedcharged group of group of covalentlycovalently bonded bonded atomsatoms Combine with ions of opposite charge to form Combine with ions of opposite charge to form
ionic compoundsionic compounds
Ex: NHEx: NH44++, NO, NO33
--, SO, SO442-2-
Nomenclature of binary ionic compoundsSome polyatomic anions that you must know:
NO3- = nitrate NO2
- = nitrite
SO4 2 - = sulfate SO3
2- = sulfite
PO43- = phosphate PO3
3- = phosphite
CO32- = carbonate
HCO31- = hydrogen carbonate or
bicarbonate
OH- = hydroxide CN- = cyanide
C2H3O2- = acetate C2O4
2- = oxalate
III. Polyatomic IonsIII. Polyatomic Ions
Most commonMost common ion is given the ending ion is given the ending –ate–ate..Most commonMost common ion is given the ending ion is given the ending –ate–ate..
ClO3-ClO3-
• chloratechlorate• chloratechlorate ClO2-ClO2-
• chloritechlorite• chloritechlorite ClO-ClO-• hypochloritehypochlorite• hypochloritehypochloriteClO4
-ClO4-
• perchlorateperchlorate• perchlorateperchlorate
• One less oxygenOne less oxygen than than –ate–ate ends inends in –ite–ite..• One less oxygenOne less oxygen than than –ate–ate ends inends in –ite–ite..
• One less oxygenOne less oxygen than than –ite–ite is given the prefixis given the prefix hypohypo..
• One less oxygenOne less oxygen than than –ite–ite is given the prefixis given the prefix hypohypo..• One more oxygenOne more oxygen than than -ate-ate is given the prefixis given the prefix perper..
• One more oxygenOne more oxygen than than -ate-ate is given the prefixis given the prefix perper..
NO3-NO3-
• nitratenitrate• nitratenitrate NO2-NO2-
• nitritenitrite• nitritenitrite
Sample Problem 7-3
a. Write the formula for potassium sulfate.a. Write the formula for potassium sulfate.
b. Write the formula for calcium carbonate.b. Write the formula for calcium carbonate.
c. Write the formula for tin(IV) sulfate.c. Write the formula for tin(IV) sulfate.
potassium chloride
magnesium nitrate
copper(II) chloride
K+ Cl
Mg2+ NO3
Cu2+ Cl
KCl
Mg(NO3)2
CuCl2
Ionic Nomenclature Practice
Nomenclature of binary ionic compounds
NaHCO3 K2SO3 MgSO4 KCN H2PO4
Ca(OH)2 NH4NO3 Zn(NO3)2 Li3PO4 HNO3
Naming salts composed of the polyatomic ions is the same as with the monatomic anions. Metal name then polyatomic name.
NaOH sodium hydroxide Ba(NO3)2 barium nitrateH2SO4 hydrogen sulfate CsNO2 cesium nitrite
Sometimes there is a common name:KHCO3 potassium hydrogen carbonate or potassium bicarbonate
Note: the polyatomic anions must be memorized.
Name the following ionic compounds: