Chapter 2 Topics:
Elements and the Periodic Table
http://www.youtube.com/watch?v=1PSzSTilu_s
Can you find the halogens? Alkali metals? Noble gases? Transition
metals? Alkaline earth metals? Lanthanides and actinides? Metals?
Nonmetals? Semimetals or metalloids?
Balancing Equations
What coefficients balance this equation:
Mg + Al2S3 → Al + MgS
Types of Reactions
Classify the reaction type above.
Subatomic Particles!
Particle
Charge
Mass
Location
Electron
-1
1/1800
Outside the
nucleus
Proton
+1
1
Inside the
nucleus
Neutron
0
1 + 1/1800
Inside the
nucleus
Atomic number is the number of
protons. This tells WHAT element it is!
The number on the
Periodic table is the
ATOMIC WEIGHT.
This is an average
mass of all the
ISOTOPES that
occur in nature.
Atomic mass or mass
number is a WHOLE
number that must be
rounded from the
number on the periodic
table. It is the
number of protons + the
number of neutrons
in an atom of the
element.
Isotopes are atoms of the same element that have
different MASSES. They have the same number
of PROTONS, but different numbers of NEUTRONS.
Isotope
Notation!
Isotopes of an
element have
the same physical
and chemical
properties. They
only have different
MASSES!
40
20Ca
How many protons? What is the atomic
number? What is the mass number? How many
neutrons? How many electrons? (Hint: All atoms
must be neutral!)
21Ne
How many protons? How many neutrons?
How many electrons?
19
9X
How many protons? How many neutrons?
What element is this?
An isotope of an element has 3 protons and 4
neutrons. Write its isotope notation.
ATOMIC
WEIGHT
Lithium exists as two isotopes: lithium-7 and lithium-6
Lithium-7 has a mass of 7.015 amu and makes up
92.58% of lithium
Lithium-6 has a mass of 6.015 amu and makes up
7.42%
What is the atomic weight of lithium (on the
periodic table)? Which isotope is more abundant,
lithium-6 or lithium-7?
To calculate the average atomic mass of lithium,
multiply the mass of each isotope by its abundance,
then add these 2 values to each other
Mass Defect
There's actually one more reason
why the mass isn't a whole number....
recall that the mass of a neutron isn't
exactly 1 amu. And when protons
and neutrons stick together
to make a nucleus, a small
amount of mass is
converted to energy, making
a very strong bond called
strong nuclear force.
E=mc2
When an
atom loses
electrons it
becomes a
positively
charged ion
called a
cation.
IONS
Atoms are neutral
because they have the
same number of
protons and electrons.
When an
atom gains
electrons it
becomes a
negatively
charged ion
called an
anion.
39K+
How many protons does this isotope have?
How many neutrons?
How many electrons does this ion have?
16O2-
How many protons does this isotope have?
How many neutrons?
How many electrons does this ion have?