Download Chapter 3: Atomic Theory

III. ATOMS
A. Atomic Components and Standard Notation
1. Interaction of Electrical Charges
a) Opposites attract, likes repel.
+ and - attract
+ and + repel
- and - repel
b) Force depends on the distance and the size of the charges
2. Atomic Components
NAME
ABBREVIATION
CHARGE
proton
neutron
electron
p
n
e-
+1
0
-1
RELATIVE
MASS
1
1
0.00055
3. Arrangement
p’s and n’s together in the nucleus, e-‘s orbit the nucleus (according to the Bohr
model)
4. Atomic number is the number of protons in the atom. (Note in Standard Notation
the
atomic number is written in the lower left-hand corner.)
The number of protons determines the identity, not n’s or e -‘s or color, or even the
symbol.
6C
9F
12Mg
What element is 9X ?
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5. Atomic mass number is the number is protons + neutrons.
(2): How many p’s and n’s are in
12
6
C
6. Isotopes are atoms of the same element with a different number of neutrons or
mass
number.
(3): How many neutrons are in each of the following atoms of carbon?
11
6
C
12
6
C
13
6
14
6
C
C
Isotope does not mean radioactive, while some isotopes are radioactive, the vast
majority of isotopes are not.
7. Number of electrons in neutral atoms
ALL elements are electrically neutral !
(4): What is the charge on the element sodium
11Na
?
(5): What is the charge on the element chlorine 17Cl ?
(6): How many protons, neutrons and electrons are in the element
27
13
Al
8. Number of electrons in ions
a) Ion is an atom with a net electrical charge.
An ion cannot exist on its own, it is always part of a compound !
NaCl is Na1+ with Cl1- , NaCl is a compound, not an element
Na+1 cannot exist on its own, Cl1- cannot exist on its own.
c) Negative ions (anions)
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(9): How many electrons are in a chlorine atom, how many electrons are is a chloride
ion, 17Cl1-?
(10): How many electrons are in a sulfur atom, how many electrons are is a sulfide ion.
216S ?
b) Positive ions (cations)
(7): How many electrons are in a sodium atom, how many electrons are in a sodium
ion, 11Na1+?
(8): How many electrons are in an aluminum atom, how many electrons are in an
aluminum ion, 13Al3+?
d) Summary
(11): How many p’s, n’s and e-‘s are in
(12): Which is an isotope of
104
53
X
3+
104
54
X
3+
104
54
104
54
X
3+
?
X
2+
105
54
X
3+
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B. Electron Configuration
1. Bohr Model
a) The electron(s) circulate the nucleus in orbits or shells
b) There are a number of orbits or shells around the nucleus, each larger than the
preceding.
c) The orbits or shells are labeled with either a number (n) or a letter
n
letter
1
K
2
L
3
M
4
N
5
O
etc.
etc.
d) The orbits or shells are also called energy levels – the bigger the orbit the
more energy the electron has.
e) Each orbit (or energy level) has a maximum capacity, given by 2x(n 2)
n
1
2
3
4
5
6
7
max # e-‘s
2
8
18
32
?
?
?
(1): What is the maximun number of electrons that can be held by the fifth energy level?
2. Electron Configuration
(2): Draw the Bohr diagram for
4
2
(3): Draw the Bohr diagram for
12
6
(4): Draw the Bohr diagram for
32
16
He
C
S
3. Short Notation
He
2
C
2-4
S
2-8-6
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C. Periodic Table and periodic Properties
1. Construction of Periodic Table
1
H
1
He
2
Li
2-1
Be
2
Na
Mg
B
2-2
2-3
C
N
2-4
Al
Si
O
2-5
F
2-6
Ne
2-7
2-8
P
S
Cl
Ar
3
2-8-1
2-8-2
2-8-3
2-8-4
2-8-5
2-8-6
2-8-7
2-8-8
4
5
6
7
a) Period number = the number of occupied orbits (or energy levels)
b) Group number = the number of outer electrons
c) Outer electrons are called valence electrons. The only electrons that are
involve in the formation of compounds are the valence electrons
d) For ALL Main group atoms the group number tells the number of valence
electrons, and the period number tells in which orbit they are located.
(1): What is the electron configuration of
19K?
(2): How many valence electrons are in 33As, and in which orbit are they located?
(3): How many valence electrons are in 56Ba, and in which orbit are they located?
(4): Which atom has 3 valence electrons in its 5th orbit?
- 22 2. Periodic properties
a) Atoms from the same group tend to form compounds with the same formula.
I
HCl
LiCl
NaCl
KCl
II
BeCl2
MgCl2
CaCl2
III
IV
V
BCl3
CCl4
NCl3
AlCl3 SiCl4 PCl3
GaCl3 GeCl4 AsCl3
VI
VII
OCl2
SCl2
SeCl2
FCl
BrCl
b) When forming compounds, atoms will take on or give up electrons until their
outer orbit (or energy level) is filled. Except for H and Li this means 8
electrons. H and Li are filled when their outer orbits have 2 electrons.
(5): When Na forms a compound what would you expect it to do to achieve 8 outer
electrons?
(6): When Ca forms a compound what would you expect it to do to achieve 8 outer
electrons?
(7): When 31Ga forms a compound what would you expect it to do to achieve 8 outer
electrons?
(8): When F forms a compound what would you expect it to do to achieve 8 outer
electrons?
(9): When S forms a compound what would you expect it to do to achieve 8 outer
electrons?
c) In general. metals lose their valence electrons, nonmetals gain electrons
in order to achieve 8 electrons.
H is a special case, since it valence orbit can hold only 2 electrons, it tends to take on 1
electron, and ends up with a filled orbit with 2, NOT 8, electrons.
- 23a d) Electronegativity is a measure of an atoms ability to gain electrons.
EN is a relative scale that runs from 0 to 4 (like a grade point index).
The higher the value, the greater the ability to take on electrons.
Metals have relatively low EN’s
Nonmetal have relatively high EN’s
e) En increases from left to right, and from bottom to top.
(10): Of all the atoms, which has the highest EN
(11): In period 3, which atom has the highest EN, Na, Al, Cl. or Ar?
(12): In Group VI, which atom has the highest EN?
(13): In Group V, which atom has the lowest EN?
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