Download ATOMIC MASS

•What is the chemical formula for
water?
Draw the structure of water.
Write down all the types of
bonding that you know of.
What allows
this drop of
water to
hang there
without
falling?
Surface Tension
Hydrogen Bonding in Water
Chemical Context of Life
 Matter (space & mass)
 Element; compound
 The atom
 Atomic number (# of
protons); mass number
(protons + neutrons)
 Isotopes (different # of
neutrons); radioactive
isotopes (nuclear decay)
 Energy (ability to do work);
energy levels (electron
states of potential energy)
Chemical Bonding
Covalent
Double covalent
Nonpolar covalent
Polar covalent
Ionic
Hydrogen
van der Waals
Covalent Bonding
 Sharing pair of valence
electrons
 Number of electrons
required to complete an
atom’s valence shell
determines how many
bonds will form
 Ex: Hydrogen & oxygen
bonding in water;
methane
Covalent bonding
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Polar/nonpolar covalent bonds
Electronegativity
attraction for electrons
Nonpolar covalent
•electrons shared equally
•Ex: diatomic H and O
Polar covalent
•one atom more
electronegative than
the other (charged)
•Ex: water
Polar/nonpolar bonds
Ionic bonding
 High electronegativity
difference strips
valence electrons away
from another atom
 Electron transfer
creates ions (charged
atoms)
 Cation (positive ion);
anion (negative ion)
 Ex: Salts (sodium
chloride)
Ionic bonds
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Hydrogen bonds
Hydrogen atom
covalently bonded to
one electronegative
atom is also attracted
to another
electronegative atom
(oxygen or nitrogen)
van der Waals interactions
Weak interactions between molecules or
parts of molecules that are brought about
by localized change fluctuations
Due to the fact that electrons are
constantly in motion and at any given
instant, ever-changing “hot spots” of
negative or positive charge may develop
Water
 Polar~ opposite ends, opposite charges
 Cohesion~ H+ bonds holding molecules
together
 Adhesion~ H+ bonds holding molecules to
another substance
 Surface tension~ measurement of the
difficulty to break or stretch the surface of a
liquid
 Specific heat~ amount of heat absorbed or
lost to change temperature by 1oC
 Heat of vaporization~ quantity of heat
required to convert 1g from liquid to gas
states
 Density……….
Density
Less dense as solid
than liquid
Due to hydrogen
bonding
Crystalline lattice
keeps molecules at a
distance
Acid/Base & pH
 Dissociation of water into a
hydrogen ion and a hydroxide
ion
 Acid: increases the hydrogen
concentration of a solution
 Base: reduces the hydrogen
ion concentration of a solution
 pH: “power of hydrogen”
 Buffers: substances that
minimize H+ and OHconcentrations (accepts or
donates H+ ions)
Two major parts of an atom
Nucleus
(not to scale)
Electron
Cloud
Three Major
Sub-Atomic Particles
• Protons
• Neutrons
• Electrons
PROTON
+
(p )
a single, relatively large
particle with a
positive charge that is
found in the nucleus
THE PROTON
• Fat
(heavy)
+
p
• Positive 
(charge)
• Doesn’t move
(lazy)
NEUTRON (N°)
a single, relatively large
particle with a
neutral charge that is
found in the nucleus
THE NEUTRON

°
N
• Fat
(heavy)
• Neutral 
(charge)
• Doesn’t move
(lazy)
ELECTRON
(e )
a single, very small
particle with a
negative charge that is
found in a “cloud”
around the nucleus
THE ELECTRON
• Skinny
(very light)
e
• Negative 
(charge)
• Moves a lot
(runs around)
Review: Subatomic Particles
+
p

°
N
e-
Please complete the following table
Protons
Neutrons Electrons
Where are
they found?
Nucleus
Nucleus
Electron
Cloud
Mass
Heavy
Heavy
Very Light
Charge
(attitude)
Positive 
Neutral 
Negative 
ATOMIC MASS #
(A)
The total mass of all of
the subatomic particles
in an atom
(but really # of protons and
neutrons)
ATOMIC NUMBER
(Z)
the number of protons
in an atom
(assuming the atom is
+
neutral, # of p = # of e )
Example: Sodium
Atomic Mass # =
+
p &
22.99
Na
11
Atomic # = # of protons
°
N
Another Notation
Atomic Mass # =
+
p &
Atomic # = # of protons
°
N
To calculate the number
of neutrons, subtract the
atomic number (smaller)
from the atomic mass
number (larger)
A – Z = # of neutrons
Ex: How many neutrons
does Sodium have?
Mass # - Atomic # = #N°
(You may need to round the atomic #)
22.99
Na
11
23 - 11 = 12
N°
ION
Atoms of the same
element that differ in
charge.
(They have the same # of
+
p , but different # of e )
Positive Ions Negative Ions
(cations)
(anions)
•
2+
• Ca (lost 2 e )
3+
• Al (lost 3 e )
4+
• Pb (lost 4 e )
+
• H (lost 1 e )
•
2• O (gain 2 e )
3• P (gain 3 e )
2• S (gain 2 e )
• OH (gain 1 e )
+
Na (lost 1 e )
Cl (gain 1 e )
If an atom GAINS
electrons, its overall charge
becomes more negative.
If it LOSES electrons, its
charge becomes more
positive
ISOTOPE
Atoms of the same
element that differ in
mass.
(They have the same # of
+
p , but different # of N°)
Isotopes are
CHEMICALLY the
SAME as atoms, but
DIFFER PHYSICALLY
because they have
different masses.
A few examples of isotopes…
Complete the following table
Protons
Na+
Br w/ mass
84
O2- with
mass 13
Neutrons
Electrons