Download The Atom Notes

The Atom
What to look for:
Three Essential Questions
E. Q. #1 = What are the parts of an atom?
E. Q. #2 = In what manner can subatomic particles be differentiated?
E. Q. #3 = How does the atomic structure impact chemical change &
reactivity?
The Building Block of Matter
 400 BC
Democritus (Greek Philosopher)
 Atomos = “indivisible”
 …like a brick is used to build a building; an
atom is used to build all matter…
First Atomic Theory


1808 John Dalton (English Chemist)
Using experiments formulates the first
atomic theory
1. All elements are composed of indivisible
particles called atoms
2. Atoms of the same elements are exactly the
same
3. Atoms of different elements are different
4. Two or more elements combine to form
compounds
Subatomic Particles
The idea that the atoms was not a solid
sphere, but a composition of small particles
which came to be known as subatomic
particles
 Julius Plucker, William Crooks & J J Thomson
mid-1800’s
J J Thomson
 1897 Discovers the electron
Ernest Rutherford (English Physicist)
 Gold Foil Experiments
 1908 Discovers that the
atom is mostly empty
space
 Discovers a hard, dense
center of the atom called
the NUCLEUS
The Gold Foil Experiment
The atom is mostly empty space
 Most of the particles passed straight
through to gold foil.
 First important discovery by Rutherford
The NUCLEUS is Discovered
 1911 Rutherford proves that the particles that
do not pass through are hitting a small, dense
center of the atom called the nucleus.
 Rutherford later goes on to discover the proton
3
Name three major discoveries made by Ernest
Rutherford & the Gold Foil Experiment:
1. _______________________________________
2. _______________________________________
2
1
3. _______________________________________
What are the two results of firing particle at atoms in
the foil of the Gold Foil Experiments:
1. _______________________________________
2. _______________________________________
Who was the first to attempt to form a complete atomic theory?
1. _______________________________________
Electron Energy Levels
 1913 Niels Bohr (Danish physicist) discovers
the electrons travel around the outside of the
atom on different energy levels
 The Bohr Model = “solar system” model
The Neutron is
Found
 1932 James Chadwick proves
the existence of the neutron.
 Only 4 years later the neutron is
used to split the first atom
 Why was the neutron’s existence
more difficult to prove?
 What evidence hinted of its
existence? “the missing mass”
E. Q. #1 = What are the parts of an atom?
The Subatomic Particles
Particle
Location
Mass
(AMU)
Charge
Electron
Electron
Cloud
0
negative
Proton
Nucleus
1
positive
Neutron
Nucleus
1
neutral
E. Q. #2 = In what manner can subatomic particles be differentiated?
Finding the Number
of Subatomic
Particles in an Atom
 Atomic Number = the number of protons in
the nucleus of an atom
 Identifies each element
 Hydrogen is 1 and it has 1 proton in its
nucleus (only hydrogen has 1 proton)
 Helium is 2 and it has 2 protons in its
nucleus (only helium has 2 protons)
Electrons
IF the atom is neutral (same number positive
charges as negative charges) then the number
of electrons will be the same as protons.
 ION = a charged atom (unequal number of
protons and electrons)
 +1 charge = the atom LOST one electron
 -1 charge = the atom GAINED one electron
 +2 charge = LOST 2 electrons
 -2 charge = GAINED 2 electrons and so on
Example of Ions
 Sodium will lose one electron when it bonds
 Na+1 or Na+
 Sodium’s atomic number is 11, so it has 11
protons.
 The +1 charge means Na+1 has 10 electrons
Another Example
 Chlorine will gain an electron when it bonds
 Cl-1 or Cl-
 Chlorine’s atomic number is 17, so it has 17
protons
 The -1 charge means Cl-1 has 18 electrons
Mass Number
 The two subatomic particles that have mass?
 Proton and neutron, both found in the nucleus
 Mass Number = # of Protons + # of Neutrons
Mass # - Atomic # = # of neutrons
Practice Problems
Symbol
Atomic
Number
Mass
Charge Protons Neutrons Electrons
Number
Mg
12
24
0
12
12
12
K
19
39
0
19
20
19
Na+1
11
23
+1
11
12
10
F-1
9
19
-1
9
10
10
Mg+2
12
24
+2
12
12
10
Do Parts of the Atom & Atomic Structure practice sheet now.
ISOTOPES



Atoms of the same element with a different number
of neutrons.
Ex: carbon-12 & carbon-14
Carbon-12
1.
2.
3.

6 protons
6 neutrons
6 electrons
Carbon-14
1.
2.
3.
6 protons
8 neutrons
6 electrons
Isotopes of Hydrogen
 Hydrogen-1 (protium) 0 neutrons
 Hydrogen-2 (deuterium) 1 neutron
 Hydrogen-3 (tritium) 2 neutrons
The ELECTRON
CLOUD
 The electron cloud is separated by different
energy levels.
 Electrons with less energy travel on the levels
closest to the nucleus.
 Energy levels are divided into sub-levels
 Sub-levels are divided into orbitals
 All of these levels, sub-levels & orbitals can
overlap.
VALENCE ELECTRONS
 Valence electrons = the outermost
electrons
 The electrons involved in bonding
 Determines the chemical properties of an
atom
E. Q. #3 = How does the atomic structure impact chemical
change & reactivity?
Do Practice sheets What Is This Atom Now? 1 & 2 now.
More about Electrons
 Maximum # of electrons on each
energy level
 Level 1 = 2 electrons
 Level 2 = 8 electrons
 Level 3 = 18 electrons
 Level 4 = 32 electrons
“the Stable 8”



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Due to the overlapping levels, sub-levels and
orbitals the maximum number of outer most
electrons is EIGHT.
An atom is becomes stable when it outer-most
energy levels is full of electrons
This explains the chemical bonding properties
of the atoms
Atoms will do one of three things in order to fill
their outer most energy levels.
1. gain electrons
2. lose electrons
3. share electrons
Concepts Coming Up Next
 The number of valence electrons an atom has
determines the group it becomes to on the
PERIODIC TABLE.
 Groups or families of elements on the periodic
table has similar chemical properties.
Concepts Coming Up Next
 Valence electrons determine how atoms will
bond with other atoms in order to complete their
outer-most energy level.
 The Stable 8
 CHEMICAL BONDING
 Ionic bonding (gaining/losing of electrons)
 Covalent bonding (sharing of electrons)