6.2 covalent bonding 6.2 continued…polar bonds! key concepts what happens when atoms don’t share...
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6.2 Covalent Bonding
6.2 Continued…Polar Bonds!Key Concepts• What happens when atoms don’t share electrons
equally?
• What factors determine whether a molecule is polar?
• How do attractions between polar molecules compare to attractions between nonpolar molecules?
6.2 Covalent Bonding
• In general, atoms on the _______ side of the table have a greater attraction for electrons
• _____________ is the most electronegative element
• Why are the noble gases crossed off?
right
fluorine
Their outer energy levels are full
6.2 Covalent Bonding
Because some atoms are better at attracting electrons than others, sometimes electrons are shared _________________
Unequal Sharing of Electrons
HCl
H Cl
In hydrogen chloride, which atom looks like it has more electrons around it?
These atoms acquire ____________ charges
unequally
chlorine
partial
δ – δ +
6.2 Covalent Bonding
When atoms share electrons ________________, the covalent bond is called a ______________ covalent bonds
Unequal Sharing of Electrons
HCl
H Cl
Polar means “opposite” in characterδ – δ +
unequally
polar
6.2 Covalent Bonding
This is similar to the polar bear and the penguin…who has the ice cream more often?
Unequal Sharing of Electrons
HCl
H Cl δ – δ +
The polar bear (chlorine)
6.2 Covalent Bonding
If this was an ionic bond, how would the picture be different?
Unequal Sharing of Electrons
The penguin would GIVEAWAY the ice cream
No sharing!
6.2 Covalent Bonding
Bond types can be determined by calculating the ______________ in the bonded atom’s electronegativity values
Nonpolar covalent
less than 0.5
Polar covalent
0.5 to 2.0
Ionic
greater than 2.0
Electronegativity Table
difference
6.2 Covalent Bonding
What type of bond is H – H ?
Nonpolar covalent
less than 0.5
Polar covalent
0.5 to 2.0
Ionic
greater than 2.0
Electronegativity Table
2.1 – 2.1 = 0
nonpolar covalent
6.2 Covalent Bonding
What type of bond is C – O ?
Nonpolar covalent
less than 0.5
Polar covalent
0.5 to 2.0
Ionic
greater than 2.0
Electronegativity Table3.5 – 2.5 = 1.0
Polar covalent
6.2 Covalent Bonding
What type of bond is Na – Cl ?
Nonpolar covalent
less than 0.5
Polar covalent
0.5 to 2.0
Ionic
greater than 2.0
Electronegativity Table
3.0 – 0.9 = 2.1
Ionic
6.2 Covalent Bonding
Polar and Nonpolar Molecules
When a molecule has more than two atoms, two factors will determine whether or not the molecule is polar…• ________ of atoms• ____________ of the molecule
Unequal Sharing of Electrons
type
shape
6.2 Covalent Bonding
In a carbon dioxide (CO2)
molecule, the polar bonds ______________ out because the molecule is straight in shape or _________________.
So this entire molecule is considered ________________
Kind of like a game of tug-o-war that ___________ is winning
Unequal Sharing of Electrons
δ + δ - δ -
3.5 2.5 3.5
O = C = O
cancel
linear
nonpolar
no one
6.2 Covalent Bonding
In a water (H2O) molecule, the
polar bonds do ________ cancel out because the molecule is___________.
Or in other words, one side of the water molecule is still partially ________________ while the other side is still partially _________________
Unequal Sharing of Electrons
δ –
δ + δ +
2.1 H
2.1 H
O3.5
NOT
bent
positive
negative
6.2 Covalent Bonding
Polar molecules, due to their opposite charges, can also attract ________ _______________ and form additional bonds
Due to the attraction between polar molecules, water exhibits…• ___________ tension• a __________ boiling
point than other molecules
similar to it in size
Attraction Between Molecules
one another
surface
higher
6.2 Covalent Bonding
Surface Tension
6.2 Covalent Bonding
The attractions between polar molecules are _______________ than the attractions among nonpolar…but nonpolar attractions do ____________
They explain why CO2 and N2, both normally __________, can be stored as solids or liquids at ___________ temperatures and ___________ pressures
Attraction Between Molecules
stronger
exist
gases
lower higher
6.2 Covalent Bonding
Assessment Questions
1. What is the difference between a polar and nonpolar molecule?
Partial opposite charges
Partial chargescancel out
6.2 Covalent Bonding
Assessment Questions
2. What determines whether a molecule is polar?a. type of atoms and shape of moleculeb. mass of atoms and number of valence electronsc. type and mass of atomsd. ionization energy and number of covalent bonds
6.2 Covalent Bonding
Assessment Questions
3. Why does water have a much higher boiling point than methane? a. Methane molecules are more polar, so its molecules
have stronger attractive forces.
b. Partial charges on the polar water molecules increase attractive forces between molecules.
c. A water molecule has much more mass than a methane molecule, so water has a higher boiling point.
d. Water has a higher boiling point because its molecules do not contain carbon atoms.