Download Atomic Structure

Atomic
Structure
Part
2
1
Recap
• Atom is a particle which is
electrically neutral
• No. of protons = No. of electrons
• An atom consists of 3 subatomic
particles:
1) Protons
2) Neutrons
3) Electrons
2
Recap
• Structure of an atom
Electrons
+
Nucleus
Protons
and
Neutrons
• Relative charges and approximate
relative masses of protons,
neutrons and electrons
3
Particle
Charge
Relative Mass
Remarks
Proton
+1
1
• Mass is the same as that
of a hydrogen atom
• Found in the nucleus of
the atom
Neutron
0
1
• Mass is the same as that
of a hydrogen atom
• Found in the nucleus of
the atom
Electron
-1
1/1836
• One hydrogen atom
weighs as much as 1836
electrons
• Found around the
nucleus.
4
Recap
• Symbol of an atom
Nucleon Number
Chemical
Symbol
Proton Number
5
Recap
• Proton number (atomic number)
The number of protons in an
atom
• For an atom,
no. of protons = no. electrons
6
Recap
• Nucleon number (mass number)
= no. of protons + no. neutrons
• No. of Neutrons
= Nucleon number – Proton number
7
Overview of topic
Electronic
Structure
and the
Periodic
Table
Electronic
Arrangement
Ions
Structure
of Atoms
Atomic
Structure
Isotopes
8
Today’s Menu
• What are isotopes
• Electrons arrangement
in atoms
• Electronic structure
• Outermost electrons
• The Periodic table
9
What are isotopes?
10
What are isotopes
Isotopes:
Atoms of the same element
having the same number of
protons but different number of
neutrons
11
What are isotopes
Isotopes:
• Same number of protons
(atomic number)
• Different number of neutrons
• Different number nucleon
number
• Same number of electrons
12
Examples of isotopes
• Three isotopes of hydrogen
1)
Hydrogen
Number of proton: 1
Number of neutrons: 0
Nucleon number: 1
Hydrogen-1
Number of electron: 1
13
Examples of isotopes
• Three isotopes of hydrogen
2)
Deuterium
Number of proton: 1
Number of neutrons: 1
Nucleon number: 2
Hydrogen-2
Number of electron: 1
14
Examples of isotopes
• Three isotopes of hydrogen
3)
Tritium
Number of proton: 1
Number of neutrons: 2
Nucleon number: 3
Hydrogen-3
Number of electron: 1
15
Examples of isotopes
•Two isotopes of Chlorine
35
17
Number
Number
Nucleon
Number
Cl
of proton: 17
of neutrons: 18
number: 35
of electron: 17
Chlorine-35
37
17
Number
Number
Nucleon
Number
Cl
of proton: 17
of neutrons: 20
number: 37
of electron: 17
Chlorine-37
16
What are isotopes
Isotopes
1
1
2
1
3
1
H
H
H
Number of
Protons
Neutrons
Electrons
1
0
1
1
1
1
1
2
1
17
What are isotopes
Isotopes:
• All isotopes of the same element
have the same chemical properties
but small differences in physical
properties
• There are two types of isotopes
(i) Radioactive
(ii) Non-radioactive
18
Why does chlorine
has a nucleon number
of 35.5
19
Why does chlorine has a nucleon
number of 35.5
In the periodic table, chlorine
is denoted as
35.5
17
Cl
20
Why does chlorine has a nucleon
number of 35.5
• 75% of all chlorine atoms have a
mass of 35
• 25% of all chlorine atoms have a
mass of 37
• Average mass of one chlorine atom
= (75%  35)  (25%  37)
= 35.5
100%
21
Practice Time
Part 3 Worksheet 2
22
Electrons
Arrangement In
Atoms
23
Electrons Arrangement in Atoms
• Electrons move around
the nucleus of the atom
• The electrons are held in
shells since it is of
opposite charge
• The attractive force
between the positive
charge on the nucleus
and the negative charge
on the electrons is called
electrostatic force.
24
Electronic
Structure
25
Electronic Structure
• The way the electrons are arranged
is called its electronic structure
• Electrons are arranged in shells
which are numbered from the
nucleus onwards
• Each shell is capable of holding up
to a certain number of electrons
26
Electronic Structure
• Electrons are arranged in shells which
are numbered: 1, 2, 3, 4 from the
nucleus onwards
Shell no.
Maximum no. of
electrons
Name
1
2
Duplet
2
8
Octet
3
8
(for atoms with
proton number
 20)
Octet
27
Electronic Structure
Nucleus
1st shell
2 electrons
2nd shell
8 electrons
3rd shell
8 electrons
(proton number  20)
28
Electronic Structure
To find the electronic configuration
of an atom, we should
(1) Fill the electrons into the shell
nearest to the nucleus first.
This shell can take a maximum of
2 electrons
(2) Once this shell is filled, the
electrons go to the next available
shell which has a maximum
capacity of 8 electrons, and so
on
29
Electronic Structure
Sodium, 23
Na
11
Electronic
Configuration
2, 8, 1
Na
1st
shell
2nd
shell
3rd
shell
30
Electronic Structure
Carbon, 12
C
6
Electronic
Configuration
2, 4
C
1st
shell
2nd
shell
31
Electronic Structure
Its important to know the
electronic structure and
electronic configuration of the
first 20 elements of the
Periodic Table
32
Summary
33
Summary
1)
2)
Isotopes are atoms of the
same element having the
same number of protons but
different number of neutrons
Electrostatic force is the
force between the positive
charge on the nucleus and the
negative charge on the
electrons.
34
Summary
• Electrons are arranged in shells which
are numbered: 1, 2, 3, 4 from the
nucleus onwards
Shell no.
Maximum no. of
electrons
Name
1
2
Duplet
2
8
Octet
3
8
(for atoms with
proton number
20)
Octet
35
Summary
To find the electronic configuration
of an atom, we should
(1) Fill the electrons into the shell
nearest to the nucleus first.
This shell can take a maximum of
2 electrons
(2) Once this shell is filled, the
electrons go to the next
available shell which has a
maximum capacity of 8
electrons, and so on
36
Any
Questions
37
Practice Time
Part 3 Worksheet 2
38