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“STRUCTURE OF MATTER” Covalent Bonds Ch. 6
“STRUCTURE OF MATTER”
Covalent BondsCh. 6
MATTER Matter is
anything that has mass and occupies space.
Matter is made of atoms which are the smallest particles that have the properties of an element.
MATTER Pure substances are any
matter that has a fixed composition and definite properties.
Cannot be broken down by physical changes.
There are about 100 million pure substances that have been identified Out of these pure substances, only 118 of them are elements, the rest are compounds
MATTER
MATTER Elements are
substances that cannot be broken down into simpler substances.
Compounds are substances made of atoms of more than one element bound together.
Every compound is made up of a chemical formula
CHEMICAL FORMULAS
A chemical formula tells us:the type of atoms presentthe number of atoms presentthe type of compound
CHEMICAL FORMULASExample: table salt: Sodium Chloride
Chemical formula: NaCl
Count the atoms present:1 Na atom1 Cl atom
CHEMICAL FORMULAS Sometimes there are subscripts present.
A subscript is a small number that is in a chemical formula.
Example - water: H2O 2 H atoms 1 O atom
Subscript
CHEMICAL FORMULASSometimes there are parentheses with a subscript. The subscript only applies to the atoms within the parentheses.
Example - calcium hydroxide (kidney stones): Ca(OH)2. 1 Ca atom 2 O atoms 2 H atoms
CHEMICAL FORMULAS
Sometimes there are subscripts in the parentheses. Multiply the subscript outside the parentheses by the subscript of each element within the parentheses. If no subscript is present assume that it is 1.
Example - calcium nitrate: Ca(NO3)2 1 Ca atom 2 N atoms 6 O atoms (3 oxygens x 2 = 6)
STRUCTURE OF MATTER
Nuances in molecular structure can affect its properties. Chemical formulas can be visually represented using chemical structures which can show bond length, bond angles and atomic sizes.
STRUCTURE OF MATTER The structure of a compound
affects its properties. Example: strong bonds = high
melting points.
TYPES OF MOLECULAR STRUCTURES Network
Structures: Structure:
strong, rigid structure
Bond Strength: strong
Boiling and Melting Points: high
TYPES OF MOLECULAR STRUCTURES Ionic network
structures: Structure: regularly
shaped crystals Bond Strength:
strong Boiling and Melting
Points: high
TYPES OF MOLECULAR STRUCTURES Molecular
structures: Structure:
molecules weakly bonded together.
Bond Strength: weak
Boiling and Melting Points: low
TYPES OF MOLECULAR STRUCTURES Molecular structures
typically experience two types of attractive force:
The attraction between molecules is called intermolecular force.
It is rarely as strong as intramolecular force which is inside the molecule.
ATOMIC BONDS Atoms form atomic
bonds to become more stable.
Atoms become more stable by filling their valence shell or at least meeting the octet rule by getting 8 valence electrons.
ATOMIC BONDS There are three main types of chemical bonds
used by atoms to fill their valence shell: Covalent Metallic Ionic
“Bond,Chemical Bond”
http://edtech2.boisestate.edu/lindabennett1/502/Compounds%20and%20Naming/Ionic%20vs%20covalent.html
COVALENT BONDS
In covalent bonds, nonmetal atoms meet the octet rule by sharing one or more pairs of electrons.
The shared electron pair is called a bonding pair and represented by a line on a Lewis structure.
COVALENT BONDS
Chlorine forms a
covalent bond with
itself.
Cl2
COVALENT BONDS
Cl ClEach chlorine atom wants to gain one
electron to achieve an octet.
COVALENT BONDS
Cl ClEach chlorine atom wants to gain one
electron to achieve an octet.
COVALENT BONDS
Cl ClEach chlorine atom wants to gain one
electron to achieve an octet.
COVALENT BONDS
Cl ClThe octet is achieved by each atom sharing
the electron pair in the middle.
octetoctet
COVALENT BONDS
Cl ClThis is the bonding pair.
COVALENT BONDS
Cl ClIt is a single bonding pair so it is called a
single bond.
COVALENT BONDS
Cl ClSingle bonds are abbreviated with a dash
COVALENT BONDS
Cl Cl
This is now a chlorine molecule.
Cl2
COVALENT BONDS
Oxygen is also a
diatomic molecule
(a molecule with 2 of
the same element bonded
together).
O2
COVALENT BONDS
O OHow will oxygen bond?
COVALENT BONDS
O OHow will oxygen bond?
COVALENT BONDS
O OHow will oxygen bond?
COVALENT BONDS
O OSince each oxygen has 6 valence, they
would each need to gain 2 more electrons to be stable.
COVALENT BONDS
O OBoth pairs of electrons are shared.
COVALENT BONDS
O O6 valence electrons + 2 shared electrons = full octet
COVALENT BONDS
O OTwo bonding pairs, making a double bond.
COVALENT BONDS
O OThe double bond can be shown as two dashes.
COVALENT BONDS
O O
This is now an oxygen molecule.
O2
COVALENT BONDS Elements can share up to three pairs (6
electrons).Single Bond (2e)
Double Bond (4e)
Triple Bond (6e)
COVALENT BONDS Equal sharing of
electrons creates nonpolar covalent bonds.
Ex. Ethane, C2H6
Unequal sharing of electrons is called polar covalent bonds and can lead to molecules having a positively and negatively charged side.
Ex. Water, H20
COVALENT BONDS The slight charges on a polar molecule can
cause a loose atomic bond called polar or hydrogen bond.
COVALENT BONDS NOMENCLATURE Naming binary
covalent compounds:
Two nonmetals Name each element End the last element
in –ide Add prefixes to show
more than 1 atom or 1 atom on the second element.
# of Atoms Prefix1 mono-2 di-3 tri-4 tetra-5 penta-6 hexa-7 hepta-8 octa-9 nona-
10 deca-
COVALENT BONDS NOMENCLATURE CO
carbon monoxide CO2
carbon dioxide PCl3
phosphorus trichloride
CCl4 carbon tetrachloride
N2O dinitrogen monoxide
# of Atoms Prefix1 mono-2 di-3 tri-4 tetra-5 penta-6 hexa-7 hepta-8 octa-9 nona-
10 deca-
COVALENT BONDS NOMENCLATURE dihydrogen
monoxide H2O
nitrogen dioxide NO2
carbon tetrahydride CH4
# of Atoms Prefix1 mono-2 di-3 tri-4 tetra-5 penta-6 hexa-7 hepta-8 octa-9 nona-
10 deca-
METALLIC BONDS Metallic bonds are
metal to metal bonds formed by the attraction between positively charged metal ions and the electrons around them.
Atoms are packed tightly together to the point where outermost energy levels overlap. This allows electrons to
move freely from one atom to the next making them great conductors of electricity.
IONIC BONDS An ion is a charged atom or
molecule. It is charged because the number of electrons do not equal the number of protons in the atom or molecule. Atoms with ADDED electrons are
negative (anions). Atoms with LESS electrons are
positive (cations).
IONIC BONDS The normal charge of an ion
can be quickly determined using the oxidation number of an element. The oxidation number of an
atom is the charge that atom would have if the compound was composed of ions.
IONIC BONDS To find oxidation number:
All elements with a valence number less than four will lose all of their electrons to achieve a full valence or the octet rule. Example:
Beryllium has 2 e- Loses the 2 e- Gains a charge of +2
IONIC BONDS To find oxidation number:
All elements with a valence number greater than four will gain electrons until they have achieved a full valence or the octet rule. Example:
Nitrogen has 5 e- Gains 3 e- Gains a charge of -3
IONIC BONDS Examples:
Oxygen – Group 16 -2
Calcium – Group 2 +2
Aluminum – Group 13 +3
Chlorine – Group 17 -1
IONIC BONDS Ionic bonds are bonds formed by the attraction
between oppositely charged ions. Electrons are transferred from one element to
another.
FKPotassium (metal – cation) needs to lose 1
valence electron to drop down to a full valence shell. Fluorine (nonmetal – anion) only needs 1
electron to complete its valence shell.
FKPotassium (metal – cation) needs to lose 1
valence electron to drop down to a full valence shell. Fluorine (nonmetal – anion) only needs 1
electron to complete its valence shell.
FKPotassium (metal – cation) needs to lose 1
valence electron to drop down to a full valence shell. Fluorine (nonmetal – anion) only needs 1
electron to complete its valence shell.
FKPotassium (metal – cation) needs to lose 1
valence electron to drop down to a full valence shell. Fluorine (nonmetal – anion) only needs 1
electron to complete its valence shell.
FKPotassium (metal – cation) needs to lose 1
valence electron to drop down to a full valence shell. Fluorine (nonmetal – anion) only needs 1
electron to complete its valence shell.
Once the transfer is complete, the potassium will have a +1 charge (K+) and the fluorine will have
a -1 charge (F-).
FK+ _
FK+ _
Once the transfer is complete, the potassium will have a +1 charge (K+) and the fluorine will have
a -1 charge (F-).
FK+ _
The ionic bond is formed because of the electrostatic forces between the positive and negatively charged ions and the new overall
charge is 0.
FK
MgMagnesium (metal – cation) needs to lose 2
valence electron to drop down to a full valence shell. Iodine (nonmetal – anion) only needs 1
electron to complete its valence shell, but Mg can give to two different atoms.
I I
MgMagnesium (metal – cation) needs to lose 2
valence electron to drop down to a full valence shell. Iodine (nonmetal – anion) only needs 1
electron to complete its valence shell, but Mg can give to two different atoms.
I I
MgMagnesium (metal – cation) needs to lose 2
valence electron to drop down to a full valence shell. Iodine (nonmetal – anion) only needs 1
electron to complete its valence shell, but Mg can give to two different atoms.
I I
MgMagnesium (metal – cation) needs to lose 2
valence electron to drop down to a full valence shell. Iodine (nonmetal – anion) only needs 1
electron to complete its valence shell, but Mg can give to two different atoms.
I I
MgOnce the transfer is complete, the magnesium
will have a +2 charge (Mg2+) and each iodine will have a -1 charge (I-).
I I2+_ _
MgOnce the transfer is complete, the magnesium
will have a +2 charge (Mg2+) and each iodine will have a -1 charge (I-).
I I2+_ _
MgI I2+_ _
MgI2
IONIC BONDS Ionic bonds form
strong network structures with high melting and boiling points.
When melted or dissolved in water ionic compounds conduct electricity because ions are free to move.
IONIC BONDS NOMENCLATURE.• Name the cation (metal).
• If the first ion is a transition element other than zinc, cadmium, or silver, you must use a Roman Numeral with the name – we’ll discuss this later.
• Name the anion (nonmetal) by changing the suffix to -ide.
ExamplesNaCl
Name the metal ionSodium
Name the nonmetal ion, changing the suffix to –ide.
Chloride
CaO
Calcium Oxide
Al2S3
Aluminum Sulfide
MgI2
Magnesium Iodide
BaNa2 You should recognize a problem with this oneThis is two metals – not a binary ionic compoundThe name of this is Banana (JOKE – haha)
What is the name of this compound:
HIJKLMNO?
WATER – “H” to “O”
You have to admit – that was funny!
Banana Song
https://www.youtube.com/watch?v=ZYXTZh8CW4E
IONIC BONDS NOMENCLATURE. To go backwards from
the name to the formula you can use the “Swap and Drop” method.:
1. Write the symbols for each ion.
2. Determine the oxidation number of each ion.
3. Swap and Drop4. Reduce (if necessary).5. Rewrite
Be Fberyllium fluoride
2+ 1-
1 2
BeF2
1 1
IONIC BONDS NOMENCLATURE. To go backwards from
the name to the formula you can use the “Swap and Drop” method.:
1. Write the symbols for each ion.
2. Determine the oxidation number of each ion.
3. Swap and Drop4. Reduce (if necessary).5. Rewrite
Mg Omagnesium oxide
2+ 2-
2 2
MgO
POLYATOMIC IONS A polyatomic ion is a group of covalently
bonded atoms that have lost or gained an electron. (Example: Nitrate NO3
- and Ammonium NH4
+). Oppositely charge polyatomic ions can form
compounds. (Example: Ammonium nitrate NH4NO3).
POLYATOMIC IONS Naming of these
compounds follows the same rules as binary ionic compounds.
The most important part is recognizing there is a polyatomic ion present.
Common Polyatomic Ions
ammonium NH4+
carbonate CO32-
bicarbonate HCO3-
hydroxide OH-
nitrate NO3-
nitrite NO2-
phosphate PO43-
sulfate SO42-
sulfite SO32-
acetate C2H3O2-
POLYATOMIC BONDS To go from the
formula to the name:
1. Name the cation.2. Name the anion.
Be(NO3)2beryllium nitrate
POLYATOMIC BONDS To go from the
formula to the name:
1. Name the cation.2. Name the anion.
(NH4)2Sammonium sulfide
ammonium oxide
POLYATOMIC BONDS To go from name to formula:1. Write the symbols for each
ion.2. Determine the oxidation
number of each ion.3. Swap and Drop4. Reduce (if necessary).5. If a subscript greater than
one is added to the polyatomic ion use parentheses.
6. Rewrite
NH4 O1+ 2-
2 1
(NH4)2O( )
potassium sulfate
POLYATOMIC BONDS To go from name to formula:1. Write the symbols for each
ion.2. Determine the oxidation
number of each ion.3. Swap and Drop4. Reduce (if necessary).5. If a subscript greater than
one is added to the polyatomic ion use parentheses.
6. Rewrite
K SO41+ 2-
2 1
K2SO4
TRANSITION METAL IONIC COMPOUNDS Transition metals are cations
that have variable charges that makes them hard to name.
We use Roman numerals to indicate the charge of a transition metal.
Example: copper (II) oxide – charge of copper is +2 titanium ( IV) sulfide – charge of titanium is +4
Fe2O3
TRANSITION METAL IONIC COMPOUNDS To go from formula to
name you need to determine the Roman numeral for your transition metal:
1. If there are subscripts present use the reverse “Swap and Drop.”
2. Now use normal ionic bonding rules putting your new number in Roman numerals to the right of your transition metal ONLY.
3+ 2-
iron (III) oxide
Fe O
TRANSITION METAL IONIC COMPOUNDS To go from formula to name
you need to determine the Roman numeral for your transition metal.
1. If there are no subscripts, simply give the transition metal the equal and opposite charge to the nonmetal.
2. Now use normal ionic bonding rules putting your new number in Roman numerals to the right of your transition metal ONLY.
2-
iron (II) oxide
2+
