Download UNIT VIII - St John Brebeuf

UNIT VIII
ATOMS AND THE PERIODIC TABLE
LESSON#1
ATOMIC NUMBER, ATOMIC MASS, ISOTOPES REVIEW
VIII.1 THE STRUCTURE OF THE ATOM
Some vocabulary:
PROTONS:
(P+)
Positively charged subatomic particles
that are found in the nucleus.
NEUTRONS:
(N)
Neutrally charged subatomic particles that are ALSO
found in the nucleus.
* Elements are differentiated from one another by the
number of protons in the nucleus.
****Different number of protons….different element.***
VIII.1 THE STRUCTURE OF
THE ATOM
(e-)
Negatively charged subatomic particles
that are found in orbitals around the
nucleus.
ELECTRONS:
***like satellites orbiting the earth***
ATOMIC NUMBER:
Is the number found in the topic left hand corner of the
element on the periodic table.
Atomic # is equal to the number of protons an element
has.
What the periodic table tells
you…
11
Na
Sodium
22.99
Atomic Mass:
The Atomic Number is equal
to the # of protons (P+) in an
element.
*** Notice Atomic Mass is never a
whole number….the extra little bit is
from????
Electrons!
Atomic Mass is equal to the # of protons plus the number of neutrons.
P+ + N = Atomic Mass
Atoms vs Ions
 Atoms are neutrally charged
 Ions are either positively or negatively
charged.
 Atoms have equal number of
protons and electrons.
 Ions have different numbers of
protons and electrons.
 These inequalities determine
the ions charge.
2 Protons
4 Electrons
=
-2 Charge
VIII.1 THE STRUCTURE OF THE ATOM
IONS:
When electrons are added or taken away from an atom,
an ion is formed (charged element).
Atoms = Neutral…aka #P+ = #e-
Ex: If an extra
Chlorine atom:
# protons: 17
Ions = Charged…aka #P+ ≠ #e-
electron is added to a neutral
# electrons: 17 + 1 Extra electron = 18 e-
Charge on nucleus (Protons): +17
Charge of Electrons: -18
Total Charge of Atom: -1
VIII.1 THE STRUCTURE OF
THE ATOM
11
17
17
11
11P+
+
10e-
= +1
17P+ + 18e- = -1
VIII.1 THE STRUCTURE OF
THE ATOM
VIII.1 THE STRUCTURE OF
THE ATOM
Ex: If 2 electrons (e-) are removed from Barium (Ba)
# protons: 56
# electrons: 56 – 2 = 54
Charge on nucleus (Protons): +56
Charge of Electrons: -54
Total Charge of Atom: +2
VIII.1 THE STRUCTURE OF THE ATOM
Ex: How many electrons are possessed by Ca2+?
Find Ca on the periodic table
Ca’s atomic number is 20.
20 -2 = 18 protons
So 20 – 2 less electrons because it 2+

How many protons are in Ca+2 ?
20
VIII.1 THE STRUCTURE OF
THE ATOM
Atomic mass:
Equal to the number of protons to neutrons….mostly***
Formula:
Atomic
Number:
# P+ + N = Atomic Mass
=
Number of
Protons
Therefore:
N = Atomic Mass - # P+
THE STRUCTURE OF THE ATOM
Practice Questions
Ex: Find the number of protons, neutrons and electrons
possessed by the following atoms:
12
6
C
Atomic
number
Protons:
6
Electrons:
6
Neutrons:
6
Atomic Mass
# P+ + N = Atomic Mass
So
N = Atomic Mass - # P+
N = 12 – 6
N=6
THE STRUCTURE OF THE ATOM
Practice Questions
Ex: Find the number of protons, neutrons and electrons
possessed by the following atoms:
65
Zn3+ Protons:
30
30
Electrons:
30 -3 = 27
Neutrons:
65-30 = 35
VIII.1 THE STRUCTURE OF
THE ATOM
Isotopes: Atoms with same # of protons, but different # of neutrons;
therefore different atomic mass!
If you add a proton to an atom, a new element is
produced:
12
Carbon
+
6
proton (P+)
→
12
Nitrogen
7
If you add a neutron to an atom, you get the same
element but heavier; in other words an isotope!
12
6
C
+ n
→
13
C
6
VIII.1 THE STRUCTURE OF
THE
ATOM
Three Hydrogen-isotopes:
1.
H = H = Hydrogen
2.
H = D = Deuterium
3.
H = T = Tritium

C-isotopes:
VIII.1 THE STRUCTURE OF
THE ATOM
E. Natural Mixtures of Isotopes
Molar Mass --- is really an average value for a MIXTURE ALL POSSIBLE
isotopes.
VIII.1 THE STRUCTURE OF
THE ATOM
Ex: The following mixtures of isotopes are found in nature –
calculate the expected molar mass for the following
elements with from their isotopes.
a) Ga-69 = 60.0% , Ga-71 = 40.0%
**To get the average molar mass multiply the percentage (In decimal form)
by the molar mass for each isotope and add them together.**
Ga-69 = 0.60 X 69g/mol = 41.4 g/mol
Ga-71 = 0.40 X 71g/mol = 28.4 g/mol
Add
= 69.8 g/mol
VIII.1 THE STRUCTURE OF
THE ATOM
b) Ag-107 = 51.8%, Ag-109 = 48.2%
Ag-107 = 0.518 X 107g/mol = 55.43 g/mol
Add
Ag-109 = 0.482 X 109g/mol = 52.54 g/mol
= 107.9 g/mol
Homework
Hebden p.142-150)
P. 142 # 2
P. 144 # 9, 10
P. 146 # 13 (a,c), 14 (a,c), 15 (a,c,e,h, i)
P. 147 # 19
P. 150 # 23 (a,c,e,g)