Atoms and Ions Bohr Diagrams

Atoms and Ions
Inside the Atom
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Three sub­atomic particles
Protons: ­positive charge, heavy, inside nucleus
Electrons: ­negative charge, very light, "orbiting" nucleus
Neutrons: ­ neutral, heavy, inside nucleus
Did you know
If you could somehow squeeze all the space out of your body's atoms you would be smaller than a penny but still be as heavy.
Bohr­Rutherford Diagrams
Bohr Diagrams
Ex. phosphorus ­ 31
Steps for drawing Bohr diagrams:
Draw a circle for the nucleus and add the symbol
•
•
Draw circles around the nucleus to represent electron orbits. First orbit = 2 electrons
Second orbit = 8 electrons
Third orbit = 8 electrons (Just Remember 2,8,8)
Add dots to each orbit until the •
# of electrons = atomic number=# protons.
mass #
31
atomic #
15
P
# of Protons = atomic number
= 15
15 P
16 N
# of Neutrons = mass # ­ atomic #
= 31 ­ 15
= 16
Atoms are neutral because they have equal numbers of protons (+ve) and electrons (­ve).
Charged ions are formed when atoms gain or lose electrons.
•
Gain of electrons = negative ion = Anion
•
Loss of electrons = positive ion = Cation
n for negative
Atoms become stable ions, by gaining or losing electrons until they have 8 valence electrons (stable octet rule).
(­only 2 needed for the first orbit). Example: Do not copy
What must a sodium atom do to become stable?
t looks like a + sign
edixo
edimorb
.gnidne "edi" na teg snoinA :etoN
negyxo .xe
enimorb
Na
Protons Electrons
+ve
­ve
11
11
Sodium Atom
NOTE: Only electrons can be gained or lost, because protons are heavy, and they're stuck in the nucleus.
It must either:
a) Lose 1 electron or
b) Gain 7 electrons
Atoms become stable ions, by gaining or losing electrons until they have 8 valence electrons (stable octet rule).
(­only 2 for the first orbit). Atoms become stable ions, by gaining or losing electrons until they have 8 valence electrons (stable octet rule).
(­only 2 for the first orbit). Example: Example: What must a sodium atom do to become stable?
Take this one away
Valence electron
Na
Protons Electrons
+ve
­ve
11
11
Sodium Atom
It must either:
a) Lose 1 electron or
b) Gain 7 electrons
Na
11
Sodium Atom
It will most likely lose 1 electron
Protons Electrons
+ve
­ve
Atoms become stable ions, by gaining or losing electrons until they have 8 valence electrons (stable octet rule).
(­only 2 for the first orbit). Example: Draw Bohr diagrams for the following atoms and corresponding stable ions.
Magnesium atom
Magnesium ion
Example: +1
We now have 1 more +ve than ­ve
Na
11
Sodium
Mg
Mg
Protons Electrons
+ve
­ve
10
Sulfur atom
Sulfur ion
Ion
S
Non­metals tend to gain electrons.
Metals tend to lose electrons.
S
electrons
electrons
+
Non­metals tend to gain electrons.
Metals tend to lose electrons.
­
1
­
+
18
+1
H
+1
Li
+1
stable
2
13
+2
+3
Be
+2
Na Mg
+1
K
+2
Ca
B
+3
14
no ion
C
N
no ion
Al Si
15
­3
­3
P
16
­2
O
­2
S
17
­1
He
stable
Ne
F
­1
Cl
stable
Ar
Group 14 elements do not form ions.
Noble gases already have 8 valence electrons, so they do not form ions.