Download Atomic Structure Atomic_Structure

Physical Science BHHS 2010/Melmore
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Learning Objectives
Learning Objectives
Apply an understanding of the
structure of the atom. Be able
to interpret numbers of
subatomic particles making up
each atom.
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Atomic Models
 This model of the atom
may look familiar to
you. This is the Bohr
model. In this model,
the nucleus is orbited
by electrons, which are
in different energy
levels.
 A model uses familiar ideas to
explain unfamiliar facts
observed in nature.

A model can be changed as new
information is collected.
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ATOMIC STRUCTURE
Particle
Charge
Mass
proton
+ ve charge
1
neutron
No charge
1
electron
-ve charge
nil
Atoms are the smallest particles of an
element that retains the chemical
properties of that element
 Parts:
 Nucleus – small region in
the center of the atom.
(+ charged protons, =
charged neutrons)
 Electron Cloud – large
region, compared to
nucleus, where electrons
are found.
Size of nucleus vs. electron
cloud
If an atom was the size of a sports stadium, the nucleus
would be the size of a marble!
Subatomic Particles:
 Protons : + charge, relative mass = 1.007 atomic mass units
(amu); round to 1
 Neutrons: = charge, relative mass = 1.009 atomic mass units
(amu); round to 1
 Electrons: - charge, relative mass = 0.0005 atomic mass
units (amu); round to 0 (not factored in when figuring
total mass of an atom)
Isotopes
 Atoms with the same number of protons & electrons
but a different number of neutrons.
 They are the same element, but have different masses.
 All isotopes are used to calculate atomic mass (reason why
weight is a decimal).
 Most elements consist of a mixture of isotopes.
Atomic Number
 Number of protons in the nucleus (also the number of
electrons)
 Typically the number on top of the symbol on the
Periodic Table.
13
Al
26.981
Atomic Number
Mass Number
 Number of protons + number of neutrons in an atom.
 When solving for number of neutrons: round mass
number properly, subtract atomic number from mass
number.
Mass Number
Mass number is the number of
protons and neutrons in the nucleus
of an isotope: Mass # = p+ + n0
p+
n0
e- Mass #
8
10
8
18
Arsenic - 75
33
42
33
75
Phosphorus - 31
15
16
15
31
Nuclide
Oxygen - 18
Complete Symbols
 Contain the symbol of the element,
the mass number and the atomic
number.
Superscript →
Subscript →
X
Atomic
number
Mass
number
ATOMIC STRUCTURE
He
2
4
Atomic number
the number of protons in an atom
Atomic mass
the number of protons and
neutrons in an atom
number of electrons = number of protons
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ATOMIC STRUCTURE
Electrons are arranged in Energy Levels or
Shells around the nucleus of an atom.
•
first shell
a maximum of 2 electrons
•
second shell
a maximum of 8 electrons
•
third shell
a maximum of 8 electrons
Shells
s
p
d
1
2
2
2
6
3
2
6
10
4
2
6
10
f
g
Total
2
8
18
14
32
17
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DOT & CROSS DIAGRAMS
With Dot & Cross diagrams elements and compounds
are represented by Dots or Crosses to show electrons,
and circles to show the shells. For example;
X
Nitrogen
X X
N
XX
X X
N
7
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ELECTRONIC CONFIGURATION
With electronic configuration elements are represented
numerically by the number of electrons in their shells
and number of shells. For example;
Nitrogen
2 in 1st shell
5 in
2nd
shell
configuration = 2 , 5
2
+
5 = 7
N
7
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DOT & CROSS DIAGRAMS
With Dot & Cross diagrams elements and compounds
are represented by Dots or Crosses to show electrons,
and circles to show the shells. For example;
X
Nitrogen
X X
N
X X
N
7
14
XX
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DOT & CROSS DIAGRAMS
Draw the Dot & Cross diagrams for the following
elements;
X
8
17
X
a) O
b)
Cl 35 X
16
X
X
X
X
X
X
X X X Cl X X
X
X
X
O
X
X
X
X
X
X
X
X
X
1. How many protons does Helium have
2. How many electrons does Zinc have
3. Silver has ____electrons
4. Magnesium____electrons
5. Uranium____electrons
6. Kryption ______protons
7. Aluminium____electrons
8. Bromine ____mass
9. Calcium ____electrons
10. Sodium has ______protons
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1. What is meant when an atom is said to be in its ground state?
3. The subatomic particle(s) found in the nucleus of an atom are
5. What is the maximum number of electrons that can occupy an atomic orbital?
8. In which way do isotopes of an element differ?
9. Calcium's atomic number is 20. What does that that tell us about a calcium atom?
10. What is ALWAYS true regarding atoms of two different elements?
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1. What is meant when an atom is said to be in its ground state?
CORRECT: The state an atom is found naturally.
3. The subatomic particle(s) found in the nucleus of an atom are
CORRECT: protons and neutrons.
5. What is the maximum number of electrons that can occupy an atomic orbital?
CORRECT: 2, 6, 10, 14
8. In which way do isotopes of an element differ?
CORRECT: number of neutrons in the atom
9. Calcium's atomic number is 20. What does that that tell us about a calcium atom?
CORRECT: It has 20 protons.
10. What is ALWAYS true regarding atoms of two different elements?
CORRECT: They have different numbers of protons.
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ELECTRONIC CONFIGURATION
Write the electronic configuration for the following
elements;
a)
Ca
20
b)
Na
40
2,8,8,2
d)
Cl
17
35
2,8,7
11
23
c)
2,8,1
e)
Si
14
28
2,8,4
O
8
16
2,6
f)
B
5
11
2,3
ELECTRONIC CONFIGURATION
Write the name, electronic configuration and diagram
for the following elements;
1)
12
Mg
24
2,8,2
4)
C
2)
6
12
Ga
5)
Si
14
4
Be
8
2,2
6)
28
32
Ge
72
2,8,4
31
69
8)
2,8,18,3
10)
3)
40
2,8,8,2
2,4
7)
Ca
20
F
2,7
9
18
Al
13
26
2,8,18,4
9)
2,8,3
11)
Cl
17
34
2,8,7
B
5
10
2,3
12)
Br
35
79
2,8,18,7
DO YOU REMEMBER ?
1. The Atomic Number of an atom = number of protons in
is the............
the nucleus.
2. The Atomic Mass of an atom is
= number of Protons +
Neutrons in the
nucleus.
3. Protons in the nucleus equals
the.....
= Number of Electrons.
3. The number of Electrons =
Number of Protons
4.
shells.
Electrons orbit the nucleus in
_______
Structure of Subatomic
Particles
 Subatomic particles composed of fast moving points of
energy called quarks
Quark Calculations
(for protons and neutrons)
Each proton is 2 up quarks and 1 down quark
2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1
Each neutron is 2 down quarks and 1 up quark
2(-1/3) + 2/3 = 0
Each electron is composed of 2 down quarks
3(-1/3) = -1