Download Mass of atom

MASS OF ONE ATOM
By
Mrs. Watcharee Janpleng
MASS OF ONE ATOM

particles of atom
*one proton has mass 1.66 x10-24 g
*one neutron has mass 1.66 x10-24 g
*one electron has mass
9.1 x10-28
g
( 1 a.m.u. = 1.66 x10-24 g )
**What
is the least particles?
MASS OF ONE ATOM
MASS OF ONE ATOM
MASS OF
ONE ATOM
= mass of protons + mass of neutrons
MASS OF ONE ATOM
H
C
Na
1 amu = 1.66 x 10 -24 g
1.mass of H one atom =………………g.= ........amu
2.mass of C one atom = ……………....g.=…..amu
หรือ ......... เท่าของ H 1 อะตอม
3.mass of Na one atom =..........................g.=…..amu
หรือ ......... เท่าของ H 1 อะตอม
MASS OF ONE ATOM
1.mass of H one atom= 1.66 x10-24 g.
= 1
amu.
2.mass of C one atom= 12 x1.66 x10-24 g.
= 12
amu.
= 12 เท่าของ H 1 อะตอม
3.mass of Na one atom= 23 x1.66 x10-24 g.
= 23
amu.
= 23 เท่าของ H 1 อะตอม
1/12 mass of one atom of C-12 = 1.66 x 10-24 g.
Chemical symbol
MASS OF ONE ATOM
Element p+ n mass of one atom (g)
12
C
23
Na
32
S
56
Fe
207
Pb
(a.m.u.)
12
12x 1.66 x10-24 g
12 a.m.u.
23
23x 1.66 x10-24 g
23 a.m.u.
32
32x 1.66 x10-24 g
32 a.m.u.
56
56x 1.66 x10-24 g
56 a.m.u.
207
207x 1.66 x10-24 g
207 a.m.u.
MASS OF ONE ATOM
1. Is fact but very less value.
2. Have unit as grams ( g ).
3. Difficult to use
so it’s not rarely use.
ATOMIC MASS
ATOMIC MASS
mass of one atom
ATOMIC MASS =
1/12 mass of one atom of C-12
1/12 mass of one atom of C-12 = mass of one atom of H
=1.66 x10-24 g
= 1 a.m.u.
Masses of all other atoms are given relative to this standard mass.
Mass of one atom /Atomic mass
Element p+ n Mass of one atom Atomic mass
12
C
23
Na
32
S
56
Fe
207
Pb
12
12x 1.66 x10-24 g
12
23
23x 1.66 x10-24 g
23
32
32x 1.66 x10-24 g
32
56
56x 1.66 x10-24 g
56
207 207x 1.66 x10-24 g
207
ATOMIC MASS
***1. The comparison is not true.
****2.
no unit.
*****3. use often in chemistry.
ATOMIC MASS
3. X 4 atom have mass 1.53x10-22 g. Find atomic
mass and mass of one atom of element X .
What is element X in pereodic table.
X 4 atom
= 1.53x10-22 g.
X 1 atom
= 1.53x10-22 / 4 g.
mass of one atom = 0.3825 x 10-22 g.
atomic mass = 0.3825 x 10-22 g.
1.66 x10-24 g.
= 23.04 ≈ 23
X is
Sodium (Na )
ATOMIC MASS
4. Find atomic mass of atom Y. Then one atom of
atom Y has mass 5 times of two atom of atom
carbon ( bonus for the winner)
one atom of atom Y
=
5 times of 2 atom of C
atomic mass of atom Y = 5 x 2 x 12
= 120
ATOMIC MASS
ATOMIC MASS
ATOMIC MASS
ATOMIC MASS
ATOMIC MASS
Natural lithium is:
7.42% 6Li (6.015 amu)
92.58% 7Li (7.016 amu)
Average atomic mass of Lithium:
(7.42 x 6.015) + ( 92.58 x 7.016)
= 6.941
100
ATOMIC MASS (average)
ATOMIC MASS (average)
Isotopes
Isotopes are atoms of the same element (X) with different
numbers of neutrons in their nuclei
Atomic number (Z) = number of protons in nucleus
Mass number (A) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
Mass Number
Atomic Number
1H
1
235 U
92
AX
Z
2H
1
(D)
Element Symbol
3H
1
238 U
92
(T)
ATOMIC MASS (average)
Atomic mass= ∑ [(%abundance of isotope) (mass of isotope)]
Ex 1: The natural abundance for boron isotopes is: 19.9%
10B (10.013 amu) and 80.1% 11B (11.009amu).
Calculate the atomic weight of boron.
Atomic Mass = [(0.199)(10.013)] + [(0.801)(11.009)]
= [1.992587] + [8.818209]
= 10.810796
so, the atomic weight of B = 10.811
Atomic Mass =
∑( % of isotope)( mass of isotope)
100
Ex 1:The natural abundance for boron isotopes is: 19.9%
10B (10.013 amu) and 80.1% 11B (11.009amu).
Calculate the atomic weight of boron.
Atomic Mass = [(19.9)(10.013)] + [(80.1)(11.009)]
100
= [199.2587] + [881.8209] = 1081.00796
100
100
= 10.810796
so, the atomic weight of B = 10.811
Average atomic mass (6.941)
มวลอะตอม มวลโมเลกุล ผู้สอน: อ.ศราวุทธ แสงอุไร
46Ti
= 8.2%
47Ti
= 7.4%
48Ti
= 73.8%
49Ti
= 5.4%
50Ti
= 5.2%
The natural abundances of the isotopes of four elements
(Cl,Cr,Ge, and Sn) illustrate the diversity of isotopic distributions.
The mass number and percent abundance of each isotope are
indicated.
What is the average atomic mass of Cl?
What is the average atomic mass of Cr?
What is the average atomic mass of Ge?
มวลอะตอม มวลโมเลกุล ผู้สอน: อ.ศราวุทธ แสงอุไร
ATOMIC MASS (average)
EX The atomic mass of Lithium is 6.94, the naturally occurring
isotopes are 6Li = 6.015121 amu, and 7Li = 7.016003 amu.
Determine the percent abundance of each isotope.
Aw = [(%abundance of isotope) (mass of isotope)] +
[(%abundance of isotope) (mass of isotope)] + [….]
6.94 =[(% 6Li)(6.015121)] + [(%7Li)(7.016003)]
6.94 =[(X)(6.015121)] + [(1-X)(7.016003)]
6.94 =[6.015121X] + [7.016003- 7.016003 X]
7.016003X - 6.015121X = 7.016003 - 6.94
X = 0.075936
therefore 6Li =0.075936 x100% = 7.59% and therefore 7Li =0.924064 x100% = 92.41%
relative atomic mass
Hence the relative atomic mass of
the mass m is defined as:
Ar = m / mu
 It is now dimensionless and does
not have any units. This trick is
highly confusing and against the
standards of modern metrology.
Therefore we recommend not to
use any "relative" mass.

Answer Practice
Page 5.
2. 32 x 1.66 x10-22 g.
3.
23 ;
4. 5 x 2 x 12 = 120
5.
2
Page 6.
1. 14.0037
X is Na
เท่า
2. 28.09
3. B -10 = 20 % ; B -11 = 80 %
4. 192.254
5. Cu-63 = 72.7 % ; Cu-65 = 27.3 %