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SUMMARY
PARTS OF
THE ATOM
DISCOVERER
/YEAR EXPERIMENT
PROPOSED
ATOMIC MODEL
ELECTRON
NUCLEUS
NEUTRON ---
Joseph JohnThomson
(1897)
Cathode RayTube
Experiment
Plum PuddingModel/
Raisin BreadModel
ErnestRutherford
(1911)
Gold FoilExperiment
Nuclear Model ofthe Atom
(Rutherford Model
of the Atom)
JamesChadwick
(1932)
Bombardmentof thin sheet ofberyllium with
alpha particles
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German physicist who discovered theproton.
Eugen Goldstein
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PARTICLE MASS (g)CHARGE LOCATION
IN ATOMCOULOMBS
UNIT
CHARGE
PROTON 1.673 X 10-24 +1.602 X 10-19
NEUTRON 1.675 X 10-24 0
ELECTRON 9.109 X 10
-28
-1.602 X 10
-19
+1
0
-1
nucleus
nucleus
Outside
thenucleus
properties of the three key subatomic particles
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Atomic number
Mass number
isotopes
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Atomic number
-Atomic number (Z) is the number of protonsin the nucleus of each atom of an element
-In a neutral atom, the number of proton isequal to the number of electrons, so theatomic number also indicates the number of
electrons present in the atom
-The chemical identity of an atom can be
determined solely from its atomic number.
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https://phet.colorado.edu/sims/html/buil
d-an-atom/latest/build-an-atom_en.html
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mass number
- Mass number (A) is the total number ofprotons and neutrons in the nucleus of anatom of an element.
Mass number = number of protons + number of neutrons
Mass number = atomic number + number of neutrons
Number of neutrons
- The number of neutrons is equal to thedifference between the mass number andthe atomic number (AZ)
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Mass number = proton + neutron
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-The mass number of a particular boron atom is 12and the atomic number is 5. What is the number
of neutrons of this atom?
EXAMPLE
Given:
Mass number (A) = 12
Atomic number (Z) = 5
Number of neutrons = AZ
= 125
= 7
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DALTONS ATOMIC THEORY
1. Matter is composed of tiny indivisible spheres
called atoms.
2. Atoms of the same element are identical,
but atoms of one element are different from
those of all other elements.
3. Atoms cannot be created nor destroyed during a
chemical change.
4. Atoms of different elements combine in simple
whole number ratios to form compounds.
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ISOTOPES
-Atoms of a given element do not all have thesame mass. Most elements have two or moreISOTOPES, atoms that have the same atomicnumber but different mass number.
Example:
There are three isotopes of HYDROGEN:
Protium1 proton and no neutronDeuterium1 proton and 1 neutron
Tritium1 proton and 2 neutrons
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The accepted way to denote the atomic
number and mass number of an atom ofan element (X) is as follows:
X
A
Z
Mass number
atomic number
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Thus, for theisotopes ofhydrogen,we write:
XA
Z
Mass number
atomic number
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Example:
The two common isotopes of Uraniumwith mass numbers 235 and 238:
U238
92U235
92
With the exception of hydrogen, which hasdifferent names for each of its isotopes, isotopes
of elements are identified by their mass
numbers.
Name: Uranium-235Pronounced as
uranium two thirty-five
Name: Uranium-238Pronounced as
uranium two thirty-eight
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ISOTOPES OF CARBON:
SYMBOL NAMENUMBER OFPROTONS
NUMBER OFELECTRONS
NUMBER OFNEUTRONS
C11
6
C12
6
C14
6
C13
6
Carbon - 12
Carbon - 11
Carbon - 13
Carbon - 14
6
6
6
6
6
6
6
6
5
6
7
8
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- The chemical properties of an elementare determined primarily by the protonsand electrons in its atoms; neutrons do
not take part in chemical changes undernormal conditions:
- Isotopes of the same elements have
similar chemistries, forming the sametypes of compounds and displayingsimilar reactivities
IMPORTANT CONCEPTS
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Give the number of protons, neutronsand electrons in each of the followingspecies:
a.)
PRACTICE
Na20
11
Recall:
Superscript = mass number (A)Subscript = atomic number (Z)
Protons = 11
Neutrons = 2011 = 9
Electrons = 11
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Give the number of protons, neutronsand electrons in each of the followingspecies:
b.)
PRACTICE
Na22
11
Recall:
Superscript = mass number (A)Subscript = atomic number (Z)
Protons = 11
Neutrons = 2211 = 11
Electrons = 11
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Give the number of protons, neutronsand electrons in each of the followingspecies:
c.)
PRACTICE
O17
8
Recall:
Superscript = mass number (A)Subscript = atomic number (Z)
Protons = 8
Neutrons = 178 = 9
Electrons = 8
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Give the number of protons, neutronsand electrons in each of the followingspecies:
c.)
PRACTICE
C14
6
Recall:
Superscript = mass number (A)Subscript = atomic number (Z)
Protons = 6
Neutrons = 146 = 8
Electrons = 6
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SYMBOL
ATOMIC
NUMBER
(Z)
MASS
NUMBER
(A)
NUMBER
OF
PROTONS
NUMBER
OF
NEUTRONS
NUMBER
OF
ELECTRONS
Br 80
3 4
14 7
10 19 10
35 35 45 35
Li 3 37
7 7 7N
Ne 9 10
COMPLETE THE TABLE:
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SYMBOL
ATOMIC
NUMBER
(Z)
MASS
NUMBER
(A)
NUMBER
OF
PROTONS
NUMBER
OF
NEUTRONS
NUMBER
OF
ELECTRONS
Al 13 14
29 35
127 53
17 35
13 13
Cu 29 2964
53 53 74I
Cl 18 17
COMPLETE THE TABLE:
27
17
REFERENCES
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Chang, Raymond. 2010. Chemistry (10thedition).McGraw-Hill Companies, Inc.
Tillery, Bill. 2012. Physical Science (9thedition). McGraw-HillCompanies, Inc.
https://phet.colorado.edu/sims/html/build-an-atom/latest/build-an-atom_en.html
http://atomic-hair.net/atom.gif
http://2.bp.blogspot.com/-Xe08Ij1qo1U/TcnN1KgfSxI/AAAAAAAAAE0/dfG0jn8wRvU/s1600/boron.gif
http://upload.wikimedia.org/wikipedia/commons/6/6c/Protium deuterium tritium jpg
REFERENCES
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