Atomic
Structure
Atomic Structure

1.
2.
3.
Elements
the “stuff” of which all things are made
C, H, O and N most common in living
things
90% of all atoms on Earth are H
Atomic Structure

Element = a distinct type of atom
Hydrogen (H)
Gold (Au)
Atomic Structure
An atom is made up of 3 particles:
Protons (p+)
2. Neutrons (n0)
3. Electrons (e-)
1.
Protons
 Charge
- Positive
 Location
 Mass
+
(p )
- nucleus
– 1 atomic mass unit (amu)
Atomic Number
= # of protons an element has
Atomic Number
2
He
4.003
Atomic Number
e.x.
the atomic number of Hydrogen
is 1 because it has 1 proton
Atomic Number
What is the atomic number of Lithium?
3
How many protons does it have?
3
What is the atomic number of carbon?
6
How many protons does it have?
6
Neutrons (n0)
Charge
-none (Neutron – Neutral)
Location - nucleus
Mass – 1 atomic mass unit (amu)
Neutrons
Neutrons
Isotope = an atom of a certain element that
has a different # of neutrons
than other atoms of that element
e.g. Most C atoms have 6 neutrons (C12)
but some have 8 (C14)
Isotopes
 For
what is Carbon 14 used?
carbon dating
(radiometric dating)
Atomic Nucleus
The
nucleus contains most of
the atomic mass
protons + neutrons = Atomic
mass
Review
1. What does F stand for?
Fluorine
2. What is its atomic number ?
9
3. How many protons does it have?
9
4. How many electrons does it have?
9
Review
5. What is Fluorine's atomic mass?
19
6. How many neutrons does it have?
10
atomic mass - protons = neutrons
19 – 9 = 10 neutrons
Electrons (e-)
 Charge
- Negative
 Location – in orbit in electron shell or
cloud around the nucleus
 Mass – negligible (too small to count!)
(9.1 X 10 -31 kg)
 # electrons = # of protons
(for now)
Electrons
Valence electrons- electrons in
outermost shell of atom
Determine the properties of an
element e.g. taste, texture,
appearance, color
2. Determine how an element reacts
chemically
1.
Models of the Atom

Studies done by Chemists for years has
lead to different models of the atom
 Earnest
 Gold
Rutherford
foil experiment-discovered nucleus
 Neils
Bohr
 Schrodinger and Heisenburg
 Probability
 Louis
Cloud
de Broglie –moving matter possesses a
wavelength
Gold Foil Experiment
Models of the Atom
I.
Bohr model (planetary model)

-Neils Bohr in 1911
Electrons orbit the nucleus with different
energies (on a path, like planets orbit
the sun)
