COVALENT BONDING
WHERE ELECTRONS ARE SHARED
AND ATOMS REMAIN NEUTRAL
IONIC BONDING
ELECTRONS ARE LOST BY METAL
AND GAINED BY NONMETALS
ATOM IS A METAL
ATOM BECOMES
CHARGED
-ATOM IS A NONMETAL
-ATOM BECOMES
-CHARGED
---
+
COVALENT BONDING
SHARING OF ELECTRONS
ATOMS REMAIN NEUTRAL
OCCURS BETWEEN:
2 NONMETALS
A NONMETAL AND A METALLOID
HYDROGEN AND ALL NONMETALS
PRODUCES WEAK BONDS
PRODUCES COMPOUNDS THAT HAVE LOW
MELTING POINTS
ALL ORGANIC COMPOUNDS ARE COVALENT
COVALENT BONDINGBETWEEN
2 NONMETALS
Nonmetals, because they have more than 4 valence electrons and
especially those that have small atomic radii, will bond with themselves in order to become stable and exist at a lower energy state.
These atoms will be called DIATOMS. There are 7 diatoms
That you will need to memorize. They are F, Cl, Br, I, O, N, H.
COVALENT BONDS
Between hydrogen and
A nonmetal
Fluorine has 7 valence electrons
It needs 8 in order to exist in a lower
Energy state. It could bond ionically
With A metal or covalently with hydrogen
by sharing one of its valence electrons.
Hydrogen has only one
Electron and therefore will never
Lose that electron. In order for
It to become stable and exist
In a lower energy state, it will
Share its only electron with
fluorine
COVALENT BONDING
BETWEEN
NONMETAL AND A METALLOID
Carbon will be our only metalloid with 4 valence electrons
Fluorine is a
Nonmetal with 7
Valence electrons
The resulting stable cmpd
Contains 4 F and 1 C.
Because the atoms never
LOST E’s they remain
neutral.
POLARITY
UNEVEN DISTRIBUTION OF CHARGES
Molecules tend to be asymmetric
__
+
On polar molecules, electrons are controlled by one
Of the atoms.
Nonpolar: even distribution of charges
Molecules tend to by symmetric
Water molecules are polar = the hydrogen side of the molecule ‘feels’ more positive
Because of the absence electrons. The oxygen side of the molecule ‘feels’ more negative
Because of the presence of electrons. Here, as in all polar molecules, oxygen has 2 energy
Shells, making oxygen the ‘larger’ atom. It will control hydrogens’ electrons.
Because oxygen is controlling the electrons shared from hydrogen atoms, the electrons
Will circle around oxygen’s nucleus as well as hydrogens’ nuclei.
Oxygen’s greater presence of negative charges and energy, will cause the electrons to
Be shared unequally=polar.
+
+
_
Intermolecular forces: forces that hold molecules
(smallest part of a covalent bond) together.
In an ionic bond the opposite charges of the ions
hold the compound together. In a covalent bond
there are no opposite charges because electrons
are not lost or gained.
Hydrogen bonds: forces found between the
molecules of the water molecules.
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
O
H
H
Well how does all this connect with solutions? The reason why solutes stay in solution
is because of polarity. Polar solutes dissolve most easily in polar solvents – water is polar
and so it can dissolve all polar molecules. Nonpolar solvents dissolve nonpolar solutes.
NaCl
Cl -
Na +
Cl -
Na +
Cl -
Cl Na +
Na + Cl - Na +
Cl - Na
Na + Cl Cl +
Na + Cl - Na +
Cl - Na +
Na
+
Na + Cl Cl Cl Na +
Cl Na +
Cl Na +
Cl -
Cl -
Na +
Cl Cl -
Cl Na +
NaCl is an ionic compound
that is made up of + Na
ions and - Cl ions.
NaCl
When an ionic compound
dissolves in water it is
called DISSOCIATION.
If a non polar molecule is put into water, it will NOT dissolve because of the like
Charges that will meet in the water and the solute.
CH4 is a symmetric
molecule that is
non polar. It will not
dissolve in water
because it will be repelled
by the positive pole of
the water molecule.
In the water molecule, hydrogen has the
ability to form 4 bonds-two covalent
with oxygen and two hydrogen bonds
with oxygen of another water molecule.
Because of this, cohesion, attraction
between molecules of the same compound
occurs. We call this kind of attractive force
surface tension.
Adhesion is the attractive forces acting
between molecules of different
substances
Van der Waal forces: weaker than
Hydrogen bonds; found in polar molecules.
Solutions and suspensions:
Solutions: homogenous mixture
solute-substance being dissolved
solvent-substance dissolving
polarity
Cl
H Cl H Cl H Cl H Cl H
H
O Na O Na O Na O Na O
H
Cl
H
Cl
H
Cl
H
Cl
H
Cl
H
NaCl = Na + & Cl Each sodium ion will dissociate (move away from) from the chlorine ion. It is still an ion so it
Maintains its charge. Water is polar-hydrogen feeling more positive-oxygen feeling more neg.
Ions will ‘stick’ through opposite charges to the polar ends of the water molecule=dissolving.
Suspensions: mixture
heterogeneous
Blood:
solution: dissolved salts, proteins,
and carbohydrates
suspension: blood cells and fat
that are moved along but not
dissolved
Acids, bases, salts, buffers
Acids: forms H ions in solution.
pH 1-6
Bases: form OH ions in solution
pH 8-14
Salts: ionic metal and nonmetal
pH 7 = neutral
Buffers: weak acids and bases
Organic compounds: any compound
that contains carbon and a specific ratio
of hydrogen to oxygen.
Because carbon has 4 valence electrons
it has the capability of producing multiple
bonds with not only other elements but
with itself as well.
Living cells contain molecules that are
Made of thousand or hundred of thousand
Molecules bonded together.
These molecules are called macromolecules
Because they are so large.These molecules
are formed through a process known as
polymerization
Four macromolecules found in living cells
are:
Carbohydrates
Lipids
Proteins:
http://highered.mcgrawhill.com/sites/0072495855/student_view0/cha
pter2/animation__how_enzymes_work.html
Proteins:
Nucleic acids:
Reactions:
Dehydration: removal of water to form a
compound
Glucose + glucose
2 monosaccharides
sucrose + water
disaccharide
Neutralization: acid + base
pH: 1-6
8-14
a salt + water
7
7
Neutral cmpds
Activation energy-energy needed to start
a reaction and produce a product.
Remember= atoms bond in order to exist
at a lower energy state.
=every bond made contains
energy
=every bond broken will
release energy
=every compound needs a
specific amount of energy to be formed
ReactantsHigher energy
ProductsLower E
A=energy of the reactants
B=activation energy
C=activated complex
D=energy of the products
Exothermic rxn =
Spontaneous rxn
Energy of reactants is less than
The energy of the products
Endothermic reaction =
B
Not spontaneous.
D
A
C