CHAPTER 1: MATTER 1.1 ATOMS AND MOLECULE
LEARNING OUTCOMES
a) Write isotope notation.
b) Interpret mass spectrum.
c) Calculate the average atomic mass of an element given the relative abundance of isotopes or a mass spectrum.
d) Calculate relative atomic mass based on C-12.
Atom is the smallest unit of an element.
Particle / symbol Mass (gram) Charge Relative
An atom is made up of three subatomic particles:
(Coulumb) Charge
- Proton (p)
Electron / e 9.1 x 10-28 -1.6 x 10-19 -1
- Neutron (n)
Proton / p 1.67 x 10-24 +1.6 x 10-19 +1
- Electron (e)
Neutron / n 1.67 x 10-24 0 0
Isotopes
• Isotopes are atoms of the same element with the same number of protons in the nucleus but different number of neutrons.
• Have the same chemical properties but different physical properties.
Isotope notation: Representation of an atom
Proton number, Z
• The total number of proton in the nucleus atom.
• Also known as atomic number.
Nucleon number, A
• The total number of protons and neutrons in the nucleus of the atom.
• Also known as mass number.
Example: Find the number of neutrons, protons and electrons.
a) b) c)
n
nip
Proton:
83g
Neutron: 80
Proton:
Neutron:122
Proton:
83
Neutron:
Electron:
Electron:
78 188
Electron:
SAMZ 1
, pie toe
CHAPTER 1: MATTER
Example 1:
PIA esp ve
Example 2:
1.1 ATOMS AND MOLECULE
Species Proton Neutron Electron Notation Symbol Number of: Charge
A 2 2 2 Proton Neutron Electron
B 1 1 1
YA 200
80 Hg
28049
B 63 so 120 so
29 Cu
C 1 2 0
c You
17
O 2- 29 34
D 7 7 10
1ps 59so 3 +
8
s a 2
Co
I
27 cost
27 32 24 3t
Sometimes an element is represented by using only the nucleon number:
nucleonnumber
Atom Symbol Proton Neutron Electron Mass number Notation
Cobalt-60 Co 27
33 27 60 Eco
Phosphorus-32 P 15
Carbon-14 C 6 17
8
15
6
32
14
It
Uranium-235 U 92
143 92 235 If
Mass Spectrometry Method:
A mass spectrometer is used to determine the:
• relative atomic mass of an element 24mg 25mg 26mg
• relative molecular mass of a compound
• type of isotopes, the abundance and its relative
isotopic mass
SAMZ 2
,CHAPTER 1: MATTER 1.1 ATOMS AND MOLECULE
Calculation of Relative Atomic Mass
nounit
Step 1: Determine the average atomic mass Step 2: Compare to mass of 1/12 of carbon 12
Q = the relative abundance / percentage abundance
M = the relative isotopic mass of the element. Relative atomic/molecular/formula mass has NO UNIT!
nucleonnumber Unit: a.m.u
1. Determine the relative atomic mass of Mg. (24.33) 2. Calculate the relative atomic mass of the naturally occurring sulphur
m24,0163m25,0281ms
26,059
iq
from the following data. (32.1)
mi32,0as.mi33 a o.ts.ms34,034.24
atomic
Average mass aim
Ea
mass concustconcasitca
atomic na
Average
esnar ra
Averageatomic
mass24.3279 a.mu
atomic
average massasczato
atomic
mass
acsastx.ua
astototx.su
320924a.m.u
on
O
Average
Ar 24.3279
a.mu
naxacamu l im
µ Arti É L O
g
3. a) What is the percentage abundance of each Rb isotope? (72%,28%)
Q
a181m85,027ms87 stro
ssro.gg 100 ist 100
stro 72 stro28
b) Calculate the relative atomic mass of Rb. (85.56)
atomic
Average Sam
mass now Ea Ar 85.86a.m m
Ea
masssassiness
atomic massassassin
atomic
Average
yiaxrca.mu
Average
ist atomic
mass ftp.m.y Ar 85.86
Average
mom
SAMZ 3
, m isotopic mass
CHAPTER 1: MATTER nucleonnumber 1.1 ATOMS AND MOLECULE
4. Naturaly occurring Iridium, Ir is composed of 2 isotopes 191Ir and 193Ir 5. The ratio of relative abundance of naturally occurring chlorine is as
in the ratio of 5:8. Calculate the Ar of Ir. (192.23) follow: 35Cl/37Cl = 3.127. Calculate the Ar of chlorine. (35.48)
averageatomicmass QM averageatomicmass 8am
mm
Ir Ig aa m Yilan callas m n no so
aa m i satissitiest
a am 1922308 amy a am a.mu
35.4846
Are192.2308 Aremoxie
souses
Yax's
m ma
Ar 19223
6. Boron, B has 2 isotopes 10B and 11B. The relative atomic mass of B 7. The relative isotopic mass of 6Li and 7Li are 6.01 and 7.02
is 10.81, calculate their percentage abundance. (19%, 81%) respectively. What is the percentage abundance of each isotope if the
g relative atomic mass of Li is 6.94? (7.92%, 92.08%)
assume ios nie B 108in't m b 6ol ma707.02
stop nolo ocin.to tri 100 n
Assume
aam Sam i oui n
sa B 19010 a.am Sam
io.si acroitnoonicht sa
n two n
w.ge wutwoo in Baloon'to say no tooonot
n two n
swoon
minortas
100 B ooo 19 gq ni as.os
lost contino an
n n
a t.az
35 37
8. A sample of Chlorine consists of 76% Cl and 24% Cl. Calculate 9. A sample of chlorine consists of two isotopes 35Cl and 37Cl. The
the relative atomic mass of Chlorine. (35.48) relative atomic mass of chlorine is 35.5. Determine the percentage
missa to.me't0524 composition of each in the sample. (75%, 25%)
areypsygq.mn aam Sam sic75
II
atomic
Average mass tessitura so
tax ar 35.4s 35.5 sscustztcioo.nl
massss.xsa.mu
atomic
Average too stacioo n
3550 3521370037m 3 1 10075
3742510
SAMZ 4
LEARNING OUTCOMES
a) Write isotope notation.
b) Interpret mass spectrum.
c) Calculate the average atomic mass of an element given the relative abundance of isotopes or a mass spectrum.
d) Calculate relative atomic mass based on C-12.
Atom is the smallest unit of an element.
Particle / symbol Mass (gram) Charge Relative
An atom is made up of three subatomic particles:
(Coulumb) Charge
- Proton (p)
Electron / e 9.1 x 10-28 -1.6 x 10-19 -1
- Neutron (n)
Proton / p 1.67 x 10-24 +1.6 x 10-19 +1
- Electron (e)
Neutron / n 1.67 x 10-24 0 0
Isotopes
• Isotopes are atoms of the same element with the same number of protons in the nucleus but different number of neutrons.
• Have the same chemical properties but different physical properties.
Isotope notation: Representation of an atom
Proton number, Z
• The total number of proton in the nucleus atom.
• Also known as atomic number.
Nucleon number, A
• The total number of protons and neutrons in the nucleus of the atom.
• Also known as mass number.
Example: Find the number of neutrons, protons and electrons.
a) b) c)
n
nip
Proton:
83g
Neutron: 80
Proton:
Neutron:122
Proton:
83
Neutron:
Electron:
Electron:
78 188
Electron:
SAMZ 1
, pie toe
CHAPTER 1: MATTER
Example 1:
PIA esp ve
Example 2:
1.1 ATOMS AND MOLECULE
Species Proton Neutron Electron Notation Symbol Number of: Charge
A 2 2 2 Proton Neutron Electron
B 1 1 1
YA 200
80 Hg
28049
B 63 so 120 so
29 Cu
C 1 2 0
c You
17
O 2- 29 34
D 7 7 10
1ps 59so 3 +
8
s a 2
Co
I
27 cost
27 32 24 3t
Sometimes an element is represented by using only the nucleon number:
nucleonnumber
Atom Symbol Proton Neutron Electron Mass number Notation
Cobalt-60 Co 27
33 27 60 Eco
Phosphorus-32 P 15
Carbon-14 C 6 17
8
15
6
32
14
It
Uranium-235 U 92
143 92 235 If
Mass Spectrometry Method:
A mass spectrometer is used to determine the:
• relative atomic mass of an element 24mg 25mg 26mg
• relative molecular mass of a compound
• type of isotopes, the abundance and its relative
isotopic mass
SAMZ 2
,CHAPTER 1: MATTER 1.1 ATOMS AND MOLECULE
Calculation of Relative Atomic Mass
nounit
Step 1: Determine the average atomic mass Step 2: Compare to mass of 1/12 of carbon 12
Q = the relative abundance / percentage abundance
M = the relative isotopic mass of the element. Relative atomic/molecular/formula mass has NO UNIT!
nucleonnumber Unit: a.m.u
1. Determine the relative atomic mass of Mg. (24.33) 2. Calculate the relative atomic mass of the naturally occurring sulphur
m24,0163m25,0281ms
26,059
iq
from the following data. (32.1)
mi32,0as.mi33 a o.ts.ms34,034.24
atomic
Average mass aim
Ea
mass concustconcasitca
atomic na
Average
esnar ra
Averageatomic
mass24.3279 a.mu
atomic
average massasczato
atomic
mass
acsastx.ua
astototx.su
320924a.m.u
on
O
Average
Ar 24.3279
a.mu
naxacamu l im
µ Arti É L O
g
3. a) What is the percentage abundance of each Rb isotope? (72%,28%)
Q
a181m85,027ms87 stro
ssro.gg 100 ist 100
stro 72 stro28
b) Calculate the relative atomic mass of Rb. (85.56)
atomic
Average Sam
mass now Ea Ar 85.86a.m m
Ea
masssassiness
atomic massassassin
atomic
Average
yiaxrca.mu
Average
ist atomic
mass ftp.m.y Ar 85.86
Average
mom
SAMZ 3
, m isotopic mass
CHAPTER 1: MATTER nucleonnumber 1.1 ATOMS AND MOLECULE
4. Naturaly occurring Iridium, Ir is composed of 2 isotopes 191Ir and 193Ir 5. The ratio of relative abundance of naturally occurring chlorine is as
in the ratio of 5:8. Calculate the Ar of Ir. (192.23) follow: 35Cl/37Cl = 3.127. Calculate the Ar of chlorine. (35.48)
averageatomicmass QM averageatomicmass 8am
mm
Ir Ig aa m Yilan callas m n no so
aa m i satissitiest
a am 1922308 amy a am a.mu
35.4846
Are192.2308 Aremoxie
souses
Yax's
m ma
Ar 19223
6. Boron, B has 2 isotopes 10B and 11B. The relative atomic mass of B 7. The relative isotopic mass of 6Li and 7Li are 6.01 and 7.02
is 10.81, calculate their percentage abundance. (19%, 81%) respectively. What is the percentage abundance of each isotope if the
g relative atomic mass of Li is 6.94? (7.92%, 92.08%)
assume ios nie B 108in't m b 6ol ma707.02
stop nolo ocin.to tri 100 n
Assume
aam Sam i oui n
sa B 19010 a.am Sam
io.si acroitnoonicht sa
n two n
w.ge wutwoo in Baloon'to say no tooonot
n two n
swoon
minortas
100 B ooo 19 gq ni as.os
lost contino an
n n
a t.az
35 37
8. A sample of Chlorine consists of 76% Cl and 24% Cl. Calculate 9. A sample of chlorine consists of two isotopes 35Cl and 37Cl. The
the relative atomic mass of Chlorine. (35.48) relative atomic mass of chlorine is 35.5. Determine the percentage
missa to.me't0524 composition of each in the sample. (75%, 25%)
areypsygq.mn aam Sam sic75
II
atomic
Average mass tessitura so
tax ar 35.4s 35.5 sscustztcioo.nl
massss.xsa.mu
atomic
Average too stacioo n
3550 3521370037m 3 1 10075
3742510
SAMZ 4
