Periodic table
Each square represents a different element Contains three pieces of information:
Element symbol Atomic number Mass number
1
H
Atomic number
Number represents the number of protons in
the element’s nucleus
This will always be a whole number
Is used to identify which element you are
looking at
Atomic mass number
Not a whole number because it is the weight average
of all the masses of the naturally occurring isotopes of that element
Mass number can never be less than the atomic
number
Used to tell how many neutrons are in an element
because the mass is = # protons + # neutrons
Atomic mass unit
Commonly used for the mass of subatomic particles
and atoms
An amu is 1/12 the mass of a carbon atom which
Proton
Positively charged particle that exists in the
nucleus of an atom
The proton has a mass of 1 atomic mass units (a.m.u.) (1.673 x 10-24 g)
Most of the atom’s mass is made up from the proton
Number of protons determines which element
you are looking at
If you change the number of protons, then you change the element
Neutron
Neutrally charged particle that exists in the
nucleus of an atom
The neutron has a mass of 1 a.m.u. (1.675 x 10-24 g)
Most of the mass of an atom is made up from the neutrons
Number of neutrons can vary from atom to
atom; you still have the same element, just a different form of it
Electron
Electrons have a negative charge
The mass of an electron is approximately 0 a.m.u. (9.109 x 10-28 g)
Most of the volume is made up from the electrons Electrons exist in clouds surrounding the nucleus
The number of electrons an atom has can
change; when this happens, you still have the same element, just a different form of it
fyi
Look at a penny
If the size of the protons, neutrons, and
electrons were all the same size – it would weight 190, 000, 000 tons
The Basic Atom - most of an atom is
empty space
Protons - p+
Mass ~ 1 amu +1 charge
Neutrons - n0
Mass ~ 1 amu 0 charge
Electrons - e
- Mass ~ 1/2000 amu -1 charge
Structure of the Atom
The Subatomic Particles
Name Symbol Mass Charge Location
Proton p+ 1 amu 1+ Part of the
nucleus Neutron no 1 amu 0 Part of the
nucleus Electron e- 1/1837 amu 1- Normally at
large distances
from the nucleus
How to calculate subatomic particles
Protons = atomic number
The same as the number of protons in the nucleus of an
element; it is also the same as the number of electrons surrounding the nucleus of an element in its neutral state
# protons + # neutrons = mass number (so the
neutrons = mass number - # protons)
Electrons = protons, if the element does not have a
charge, + or - (if the element is an ion, then you have to subtract or add electrons accordingly)
1
H
practice
Calculate the subatomic particles for the
following:
Gold Lead
Modern theory of the atom
Electrically neutral sphere with a tiny nucleus
at the center, which holds the positively charges protons and the neutral neutrons
The negatively charged electrons move
around the nucleus in complex paths, all of which comprise the electron cloud
To be neutral the number of protons must
Ions
Have same number of protons, but different number of
electrons
This means that they have a charge
If the charge is positive, +, we have lost electrons (you
must subtract this number of electrons)
Cations
Metals
Become less metallic
If the charge is negative, - , we have gained electrons
(you must add this number of electrons)
Anions
Shorthand notation
12
C
6
+4
+4
A
X
+4
Z
Z = atomic number
A = mass number
Z = Atomic number
number of protons
number of electrons in neutral atom
determines which element
A = Mass Number
number of protons and neutrons
isotopes have different A values but
How many protons, neutrons, and electrons
are in:
C+4 H-1 P-3 O
Isotopes
Atoms that have the same number of protons,
but the number of neutrons have changed
These are what are commonly used in nuclear chemistry
You can tell you have an isotope because the
mass number you are using is different than what is listed on the periodic table
Practice with Subatomic particles
Isotope
Z
A Protons Neutrons
81
35
Br
81
123
12 25
Review Atomic Structure
Nuclear model of the atom
The nucleus is a dense core that contains the protons
(1+) and the neutrons (0)
The nucleus composes over 99.5% of the mass of the
atom
Only 0.5% of the mass is taken up by the electron
The nucleus occupies only about 1/100,000 of the
atom’s volume. The rest is electron space!!
Think of a marble on the 50 yard line of a football
Review
A neutral atom must have an equal number of
electrons (-) and protons (+)
If there are more electrons (-) than protons
(+) then the atom has a ____ charge – and we call it __________
If there are more protons (+) than electrons
(-), then the atoms has a ____ charge – and we call it _________
Review
Atomic number = number of protons
The number written above the element symbol in the
periodic table
Also equal to the number of electrons if the atom
is neutral
Atomic mass = number of protons + neutrons
- The number written below the element symbol in the periodic table
Review
The number of neutrons vary from atom to
atom
We determine the number of neutrons by the
subtracting the atomic number from the atomic mass
Review
Ions – atoms that have an electrical charge An atom becomes an ion by losing or gaining
electrons
Na Na+ + e- (loss of an electron) Cl + e- Cl- (gain of an electron)
Review
Isotopes have the same number of
_________ but different numbers of __________
Shorthand notation
When writing an element, its atomic number
and its atomic mass in shorthand – where
does the atomic number and the atomic mass number go?
Metals vs. nonmetals vs. metalloids
Get our a piece of paper and write your name on
it
Make three columns on your paper
Title one metals, one nonmetals, one metalloids You will look at metals, nonmetals, and
metalloids and write down physical characteristics about them.
On the back, make a venn diagram
Showing how they are similar and Different from each other
