types of chemical bonds ionic bonds covalent bonds hydrogen bonds metallic bonds
TRANSCRIPT
TYPES OF CHEMICAL BONDS
• IONIC BONDS
• COVALENT BONDS
• HYDROGEN BONDS
• METALLIC BONDS
IONIC BONDING
When an atom of a nonmetaltakes one or more electrons
from an atom of a metalso both atoms end up with
eight valence electrons
IONIC BONDING
IS THE COMPOUND AN IONIC COMPOUND?
METALMETAL NONMETAL
SUBSCRIPTS
IONIC BOND FORMATION
Neutral atoms come near each other. Electron(s) are transferred from the Metal atom to the Non-metal atom. They stick together because of electrostatic forces, like magnets.
IONIC BONDING
Metals will tend to lose electrons and become
POSITIVE CATIONS
Normal sodium atom loses one electron to become sodium ion
IONIC BONDING
Nonmetals will tend to gain electrons and become
NEGATIVE ANIONS
Normal chlorine atom gains an electron to become a chloride ion
Properties of Ionic Compounds
• Crystalline structure.
• A regular repeating arrangement of ions in the solid.
• Ions are strongly bonded.
• Structure is rigid.
• High melting points- because of strong forces between ions.
Crystalline structureThe
POSITIVE CATIONS stick to the
NEGATIVE ANIONS, like
a magnet.
Do they Conduct?
• Conducting electricity is allowing charges to move.
• In a solid, the ions are locked in place.• Ionic solids are insulators.• When melted, the ions can move
around.• Melted ionic compounds conduct.• Melting points always above 800ºC.• Dissolved in water they conduct.
Ionic solids are brittle
+ - + -+- +-
+ - + -+- +-
Ionic solids are brittle
+ - + -
+- +-+ - + -
+- +-
• Strong Repulsion breaks crystal apart.
COVALENT BOND FORMATION
When one nonmetal shares one or more electrons with an atom of another nonmetal so both atoms end up with eight valence electrons
COVALENT BONDING
IS THE COMPOUND A COVALENT COMPOUND?
NONMETALNONMETAL NONMETAL
YES since it is made of only nonmetal elementsYES since it is made of only nonmetal elements
Covalent bonding
• Fluorine has seven valence electrons
F
Covalent bonding
• Fluorine has seven valence electrons
• A second atom also has seven
F F
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons
F F
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons
F F
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons
F F
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons
F F
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons
F F
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons Both end with full orbitals
F F
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons Both end with full orbitals
F F8 Valence electrons
Covalent bonding Fluorine has seven valence electrons A second atom also has seven By sharing electrons Both end with full orbitals
F F8 Valence electrons
Single Covalent Bond
• A sharing of two valence electrons.
• Only nonmetals and Hydrogen.
• Different from an ionic bond because they actually form molecules.
• Two specific atoms are joined.
• In an ionic solid you can’t tell where the electrons came from
Water
H
O
Each hydrogen has 1 valence electron
Each hydrogen wants 1 more
The oxygen has 6 valence electrons
The oxygen wants 2 more
They share to make each other happy
Water• Put the pieces together• The first hydrogen is happy• The oxygen still wants one more
H O
Water
• The second hydrogen attaches
• Every atom has full energy levels
H OH
Two types of covalent bonds:
• Sigma bonds: represented by the symbol two orbitals with a DIRECT overlay (so it falls DIRECTLY between the nuclei of the atoms in the bond)
Two types of bondsAnother view of sigma bonds (showing electron clouds):
Two types of covalent bonds:
• Pi bonds, represented by the symbol
• two lobes of one involved atomic orbital overlap two lobes of the other involved atomic orbital.
Two types of covalent bonds
• So single bonds (or the FIRST bond formed) is a bond, and the second and/or third are always bonds
Coordinate covalent bond
• Other examples:
Polar Molecules
• Molecules with a positive and a negative end• Requires two things to be true The molecule must contain polar bonds
This can be determined from differences in electronegativity.
Symmetry can not cancel out the effects of the polar bonds.
Must determine geometry first.
Is it polar?
• HF
• H2O
• NH3
• CCl4
• CO2
Intermolecular Forces
What holds molecules to each other
Intermolecular Forces
• They are what make solid and liquid molecular compounds possible.
• The weakest are called van der Waal’s forces - there are two kinds
• Dispersion forces• Dipole Interactions
– depend on the number of electrons – more electrons stronger forces– Bigger molecules
Dispersion forces
• When electrons temporarily ‘clump’ in one part of a molecule
• Results in a temporary attractive force from a temporary dipole
Dispersion Forces
• Also called London Forces or Van der Waals forces
• The larger the molecule, the greater the additive effect
Dispersion Forces
• This is why gasoline is a solid at room temperature, but methane is a gas
Dipole interactions
• Depend on the number of electrons
• More electrons stronger forces
• Bigger molecules more electrons
• Fluorine is a gas
• Bromine is a liquid
• Iodine is a solid
Dipole interactions• Occur when polar molecules are attracted to
each other.
• Slightly stronger than dispersion forces.
• Opposites attract but not completely hooked like in ionic solids.
H F
H F
Dipole Interactions
Hydrogen bonding
• Are the attractive force caused by hydrogen bonded to F, O, or N.
• F, O, and N are very electronegative so it is a very strong dipole.
• The hydrogen partially share with the lone pair in the molecule next to it.
• The strongest of the intermolecular forces.
Hydrogen Bonding
HH
O+ -
+
H HO+-
+
Hydrogen bonding
HH
O H HO
HH
O
H
H
OH
HO
H
HO HH
O
Metallic Bonds
• Metals hold onto their valence electrons very weakly.
• Think of them as positive ions floating in a sea of electrons.
Sea of Electrons
+ + + ++ + + +
+ + + +
• Valence electrons are free to move through the solid.
• Metals conduct electricity.
Metals are Malleable
• Hammered into shape (bend).
• Ductile - drawn into wires.
Malleable
+ + + ++ + + +
+ + + +
Malleable
+ + + +
+ + + ++ + + +
• Electrons allow atoms to slide by.