CHEMISTRY
Atomic Structure
OBJECTIVES
•State the relative charges and approximate relative
masses of proton, neutrons and electrons
•Define proton number (atomic number) as the number of
protons in the nucleus of an atom
OBJECTIVES
•Define nucleon number (mass number) as the total
number of protons and neutrons in the nucleus of an atom
•Use proton number and the simple structure of atoms to
explain the basis of the Periodic Table, with special
reference to the elements of proton number 1-20
WHAT IS AN ATOM?
• Atom is the very small part of an element, which provides specific
properties of that element
• For example, gold is an element, it is composed of many gold atoms
joining together
WHAT IF WE EXAMINE
EACH INDIVIDUAL
ATOM…
• It is found that atom is
composed of subatomic
particles.
SUBATOMIC PARTICLES
• Each individual atom is
composed of subatomic
particles, including proton,
neutron and electron
PROTON, NEUTRON AND ELECTRON
Proton
Neutron
Electron
Charge
Positive charge (+ve)
Neutral
Negative charge
(-ve)
Relative mass
1
1
1/1837
Location
Nuclei
Nuclei
Around the atom
PROTON
•Located at the centre of the
atom (nuclei)
•Positively charged
Atomic diagram of helium
PROTON
• Number of proton equals to
atomic number
• From1,2,3......up to 118
• contributes to the mass
number of the element atom
Atomic diagram of helium
•How can we know the atomic
number of an element?
LOOK AT THE PERIODIC TABLE
• Top corner of the symbol
• When an atom has two protons in the
nuclei, the atomic number is 2.
• That is Helium.
QUIZ CHECK
•What element is it when
atomic number is:
i.
ii.
iii.
iv.
v.
6
8
12
17
19
PROTON, NEUTRON AND ELECTRON
-
✅
Neutron
Electron
Charge
Positive charge (+ve)
Neutral
Negative charge
(-ve)
Relative mass
1
1
1/1837
Location
Nuclei
Nuclei
Around the atom
Proton
NEUTRON
•Located at the centre of the
atom (nuclei)
•Neutral in charge
Atomic diagram of helium
NEUTRON
It is found that:
neutron in the nuclei
contributes to the mass
number of the element atom
Atomic diagram of helium
MASS NUMBER/ NUCLEON NUMBER
Number of proton +
number of neutron
Atomic diagram of helium
MASS NUMBER/
NUCLEON
NUMBER
MASS NUMBER/
NUCLEON
NUMBER
PROTON, NEUTRON AND ELECTRON
-
✅
Neutron
Charge
Positive charge (+ve)
Neutral
Negative charge
(-ve)
Relative mass
1
1
1/1837
Location
Nuclei
Nuclei
Around the atom
Proton
✅
Electron
•Moving around the nuclei,
form an electron cloud
•Negatively charged
•Always equals to the number
of proton if the atom itself is
neutrally existing
ELECTRON
ELECTRON
•It does not affect the mass of
element atom
•Determines the chemical
properties of elements
PROTON, NEUTRON AND ELECTRON
-
✅
Neutron
Charge
Positive charge (+ve)
Neutral
Negative charge
(-ve)
Relative mass
1
1
1/1837
Location
Nuclei
Nuclei
Around the atom
Proton
✅
Electron
✅
SHORT SUMMARY
• 3 subatomic particles of an atom:
proton, neutron, electron
• Proton (+ve)
- Centre of atom (nuclei)
- Atomic number
• Neutron
- Centre of atom (nuclei)
- Neutron + proton = mass number
• Electron (-ve)
- Moves around the nuclei
-
QUICK CHECK
QUICK CHECK
QUICK CHECK
QUICK CHECK
QUICK CHECK
CHECK PERIODIC TABLE
•Can you find out how do the elements are arranged in the
periodic table?
•Random/ systematic arrangement?
CHECK PERIODIC TABLE
•How are the elements arranged in periodic table?
•The arrangement of element in periodic table is based on the
number of proton.
ISOTOPE
ISOTOPE - HYDROGEN
• Number of proton = 1
ISOTOPE - HYDROGEN
• Number of proton = 1
Hydrogen
• Hydrogen and deuterium are the
same element, they have same
number of proton but different
number of neutron
Neutron
ISOTOPE - HYDROGEN
• Number of proton = 1
Hydrogen
• They have the same proton number
but a different nucleon number
Neutron
ISOTOPE - HYDROGEN
• Number of proton = 1
Hydrogen
• They have the same proton number
but a different nucleon number
• They are ISOTOPE.
Neutron
ISOTOPE - CHLORINE
• Number of proton = 17
Chlorine
ISOTOPE - CHLORINE
• Number of proton = 17
Chlorine
• Chlorine-35 and Chlorine-37 are the same
element, they have same number of proton
but different number of neutron
ISOTOPE - CHLORINE
• Number of proton = 17
Chlorine
• Chlorine-35 and Chlorine-37 are the same
element, they have same number of proton
but different number of neutron
• They are ISOTOPE.
LOOK AT CHLORINE IN
THE PERIODIC TABLE
• What does 35.5 mean?
LOOK AT CHLORINE IN
THE PERIODIC TABLE
• What does 35.5 mean?
• It is called relative atomic mass.
LOOK AT CHLORINE IN
THE PERIODIC TABLE
• What does 35.5 mean?
• It is called relative atomic mass.
• Determined by:
- relative isotopic mass
- relative abundance
EXAMPLE - CHLORINE
• It is found that there are two naturally occurring isotopes, 35Cl and
37
Cl, with relative abundances of 75.4% and 24.6% respectively.
Calculate the relative atomic mass of chlorine
EXAMPLE - CHLORINE
• It is found that there are two naturally occurring isotopes, 35Cl and
37
Cl, with relative abundances of 75.4% and 24.6% respectively.
Calculate the relative atomic mass of chlorine
35
Cl
Number of proton:
Number of neutron:
Number of electron:
37
Cl
Number of proton:
Number of neutron:
Number of electron:
EXAMPLE - CHLORINE
• It is found that there are two naturally occurring isotopes, 35Cl and
37
Cl, with relative abundances of 75.4% and 24.6% respectively.
Calculate the relative atomic mass of chlorine
Chlorine
35
Cl
37
Cl
Abundance
(%)
75.4
24.6
EXAMPLE - CHLORINE
• It is found that there are two naturally occurring isotopes, 35Cl and
37
Cl, with relative abundances of 75.4% and 24.6% respectively.
Calculate the relative atomic mass of chlorine
Chlorine
35
Cl
37
Cl
Abundance
(%)
75.4
24.6
35 x 75.4% + 37 x 24.6%
=35.5
PRACTICE
• It is found that there are three naturally occurring isotopes, 16O, 17O and 18O, with
relative abundances of 99.76%, 0.04% and 0.20% respectively.
Calculate the relative atomic mass of oxygen.
PRACTICE
• It is found that there are three naturally occurring isotopes, 16O, 17O and 18O, with
relative abundances of 99.76%, 0.04% and 0.20% respectively.
Calculate the relative atomic mass of oxygen.
Lithium
16
O
17
O
18
O
Abundance
(%)
99.76
0.04
0.20
PRACTICE
• It is found that there are three naturally occurring isotopes, 16O, 17O and 18O, with
relative abundances of 99.76%, 0.04% and 0.20% respectively.
Calculate the relative atomic mass of oxygen.
Lithium
16
O
17
O
18
O
Abundance
(%)
99.76
0.04
0.20
16 x 99,76% + 17 x 0.04% +
18 x 0.20%
=16.0044
RADIOACTIVE &
NON-RADIOACTIVE ISOTOPE
•What is radioactive?
RADIOACTIVE &
NON-RADIOACTIVE ISOTOPE
•What is radioactive?
•It is the emission of ionized
radiation or particles
RADIOACTIVE &
NON-RADIOACTIVE ISOTOPE
•Radioactive isotope:
has a very unstable nucleus
energy of radiation
decays or emits excess
•E.g. carbon-14, detect the ulcer-causing bacteria
Heliobacter pylori
RADIOACTIVE &
NON-RADIOACTIVE ISOTOPE
• Do carbon 12 and carbon 14 have same chemical properties?
Do carbon 12 and carbon 14 have same number of :
i. proton,
ii. neutron and
iii. electron?
What does it tell you?
ELECTRON
•It does not affect the mass of
element atom
•Determines the chemical
properties of elements
RADIOACTIVE &
NON-RADIOACTIVE ISOTOPE
• Do carbon 12 and carbon 14 have same chemical properties?
Do carbon 12 and carbon 14 have same number of :
i. proton,
ii. neutron and
iii. electron?
What does it tell you?
Same number of outermost electron
similar chemical properties
SUMMARY
• What is isotope?
Element atoms with They have the same proton number but a different
nucleon number
• How many types of isotopes?
Radioactive, non-radioactive
• Do both isotopes have same chemical properties?
APPLICATION
•Form a group of 3 or 4
•Find out medical/ industrial use of radioactive isotopes
•Make a PPT file for presentation (within 5 mins)
•8/3/2019 (Fri)
RADIOACTIVE ISOTOPE
Isotope
Group
Calcium 47
Cobalt 60
Copper 64
Iridium 192
Californium
252
Uranium 235
3
2
1
4
5
6
• Describe the application
• Please indicate the half life of that radioactive isotope, how does it
correspond the application?
• How should we dispose it?
WHO AND HOW TO DISCOVER
SUBATOMIC PARTICLES?
Group
•
•
•
•
Cathode-ray tube
(CRT)
Millikan’s
oil-drop
experiment
Rutherford’s
alpha-particle
experiment
Chadwick
experiment
6
5
4
3
Background (hypothesis? Anything trigger scientists’ thinking?)
Describe and explain the experiment/ model
State the significance to the development of atomic structure
Video recording with English subtitle (no more than 5 mins)
Thomson’s
Particle
plum-pudding
radiation from
model v.s.
radioactive
modern
materials
atomic model
2
1