CST Review
Day 1
“Must we do it?
I don’t want to
do it!”
Objectives
1. Atoms consist of protons,
electrons, and neutrons.
2. Elements are identified by
their atomic numbers in the
PT.
3. Mass Numbers of some
elements can differ because
of isotopes.
Atoms…
• Consist mostly of empty
space.
• Consist of three subatomic particles: protons,
electrons, and neutrons.
• Has a central region called
the nucleus where most of
the mass of the atom is
concentrated.
Nucleus
THE SUB-ATOMIC PARTICLES
Particle
Location
Charge
Protons = p+
Inside the
nucleus
Positive
Neutrons = no
Inside the
nucleus
No Charge
Electrons = e-
Outside the
nucleus; inside
electron clouds.
Negative
Number of p+ = Number of eAn ATOM carries
NO charge.
This is because
the number of
positive charges
equal the number
of negative
charges.
The number of PROTONS can NEVER change.
That means an ELEMENT will always have the
same number of protons.
Checkpoint:
1. What do we call the central region of the
atom?
2. Which two particles are found inside this
region?
3. Where can electrons be found?
4. What is the over-all charge of the atom?
5. Can the number of protons in an atom
change?
1. This particle is
most probably
the ______,
which has a
________
charge.
2. This central
region is the
_____________. It
contains two
particles:
___________ and
___________.
The atomic
number of
VANADIUM
is 23.
The Periodic Table lists all elements according to
their atomic numbers, which is the number of
protons it has.
1. How many protons does IRON have?
2. How many electrons does IRON have?
3. What is the atomic number of the element next to Iron
in the PT?
A.Which element is
this?
B.What is its atomic
number?
C.How many
electrons should
it have?
Should this
element be found
right beside the
element on the
left?
Why or Why not?
MASS NUMBER!
• The MASS NUMBER describes how “heavy” an element
or atom is. It is the total number of protons plus
neutrons in the nucleus.
This is the
collectively
the MASS
NUMBER!
35 amu
ISOTOPES…
• The number of NEUTRONS can change,
this means the mass of the element can
be different for different