PREPARED BY SIR PAUL KATIMKA 0621952008
CHEMISTRY FORM TWO FULL NOTES 2026
Page1
YOU CAN NEVER BACK TIME USE IT………………… 0621952008
, PREPARED BY SIR PAUL KATIMKA 0621952008
1st TOPIC: ATOMIC STRUCTURE
ATOM:
Is the smallest particles of matter that carry properties of element
OR
Is the smallest particle of element that take part in chemical reactions
CONTRIBUTION OF DIFFERENT SCIENTIST ABOUT ATOM
1. DEMOCRITUS (400 BC)
This Greek philosopher was the first to consider the idea that matter is made up of particles.
Such idea was not accepted because there was no experimental evidence to support it.
2 .JOHN DALTON (1803)
He used experimental evidence to convince people that matter is made up of particle called atoms
DALTON ATOMIC THEORY
There are four main points (assumption) of Dalton Atomic Theory which summarized as follows
i. Matter is made up of tiny particles called Atom.
The word atom mean unsplittable in Greek
ii. Atoms can neither be created nor destroyed
iii. Atoms of the same element are identical and have the same mass and properties while atoms of different elemen
have different properties and mass
iv. Compound are formed by a combination of two or more different kinds of atoms and always combine in in simp
whole number ratios
NOTE
Due to development o f technology modern scientist come up with slight modification to Dalton Atomic Theory
called modern concepts of Dalton atomic theory
THE MODERN CONCEPTS OF DALTON ATOMIC THEORY
i. Atom can either created or destroyed by means of nuclear reactions
ii. Some element have atoms of more than one kind which differ slightly in mass such atoms called isotopes
iii. An atom is made up of smaller sub-atomic particles called protons, neutron and electrons
iv. Atoms of different elements may chemically combine in many different ratio to form compounds
3. J.J.THOMSON (1897)
He discover the Electron among the three sub-atomic particles
According to him atom is a sphere of positive charge, with negative particles called electrons spread throughout
the sp here.
This model was referred to as plum pudding model
Figure showing J.J. Thomson plum pudding model
Page2
YOU CAN NEVER BACK TIME USE IT………………… 0621952008
, PREPARED BY SIR PAUL KATIMKA 0621952008
4. ERNEST RUTHERFORD (1917)
He discover the second sub-atomic particle called proton
Rutherford develop model of atom called planetary model
ASSUMPTION RUTHERFORDS ATOMIC MODEL
i. Protons, the positively charged particles in atom, are located in the nucleus
ii. Most of the mass of the atom is located in the nucleus.
iii. The nucleus has relatively smaller volume compared to the whole atom
iv. Electron have very small masses compared to the protons
v. Most of the space in an atom is empty
vi. Electrons are the negatively charged particle in an atom. They move around the nucleus in orbits
Rutherford’s planetary model of the atom
5. JAMES CHADWICK (1932)
He discovered the neutrons which is the third sub-atomic in an atom.
Neutrons are located in the nucleus of an atom
THE PROPERTIES OF NEUTRONS
i. They have no charge (They are neutral)
ii. They have nearly the same mass as the corresponding protons
iii. They have a mass nearly 1840 times the mass of an electron.
Location of sub-atomic particles in the atoms
SUMMARY OF THE PROPERTIES OF SUB-ATOMIC PARTICLES OF AN ATOM
Sub-atomic Symbol Location Charg Real mass Relative
particles e (g) mass
-24
Protons P In the nucleus +1 1.6726×10 1
Neutron N In the nucleus 0 1.6750 × 10 - 1
24
Electron E Outside the -1 9.109 × 10 -28
nucleus
Page3
YOU CAN NEVER BACK TIME USE IT………………… 0621952008
, PREPARED BY SIR PAUL KATIMKA 0621952008
6. NIELS BOHR (1913)
He suggested that electrons rotate around the nucleus in special regions called shells or orbits or energy levels
Each shell can only hold a specific number of electron
The maximum number of electrons held within each shell can determined by the formula 2n2, where „n’ is the
position of the shell from the nucleus
According to this formula,
First shell can hold ( electrons
Second shell can hold ( s
Third shell can hold (
Fourth shell can hold (
The first four shell are represented by the letter K, L, M and N respectively as shown in figure below
First four shells of an atom
NOTE
1. From the third shell atoms are more stable with 8 electrons even though can holds more than 8
2. First shell can hold maximum of 2 electron and if it has 2 electrons it is said to be full-filled
3. From the second shell if it contain 8 electrons it is said to be full-filled shell
4. Atom with full-filled outermost shell is said to be stable
5. Element with a maximum of 2 electrons in their outermost shells (first shell) are said to exhibit duplet state
6. Element with a maximum of 8 electrons in their outermost shell are said to exhibit octate state
ELECTRONIC CONFIGURATION
This is the arrangement of electrons in different shells in an atom
NOTE
Electronic configuration can be done by using diagram or number ratio
If diagram is used at the center (nucleus) number of protons and neutrons must be shown
Electronic configuration of some atoms using diagram
Page4
YOU CAN NEVER BACK TIME USE IT………………… 0621952008
CHEMISTRY FORM TWO FULL NOTES 2026
Page1
YOU CAN NEVER BACK TIME USE IT………………… 0621952008
, PREPARED BY SIR PAUL KATIMKA 0621952008
1st TOPIC: ATOMIC STRUCTURE
ATOM:
Is the smallest particles of matter that carry properties of element
OR
Is the smallest particle of element that take part in chemical reactions
CONTRIBUTION OF DIFFERENT SCIENTIST ABOUT ATOM
1. DEMOCRITUS (400 BC)
This Greek philosopher was the first to consider the idea that matter is made up of particles.
Such idea was not accepted because there was no experimental evidence to support it.
2 .JOHN DALTON (1803)
He used experimental evidence to convince people that matter is made up of particle called atoms
DALTON ATOMIC THEORY
There are four main points (assumption) of Dalton Atomic Theory which summarized as follows
i. Matter is made up of tiny particles called Atom.
The word atom mean unsplittable in Greek
ii. Atoms can neither be created nor destroyed
iii. Atoms of the same element are identical and have the same mass and properties while atoms of different elemen
have different properties and mass
iv. Compound are formed by a combination of two or more different kinds of atoms and always combine in in simp
whole number ratios
NOTE
Due to development o f technology modern scientist come up with slight modification to Dalton Atomic Theory
called modern concepts of Dalton atomic theory
THE MODERN CONCEPTS OF DALTON ATOMIC THEORY
i. Atom can either created or destroyed by means of nuclear reactions
ii. Some element have atoms of more than one kind which differ slightly in mass such atoms called isotopes
iii. An atom is made up of smaller sub-atomic particles called protons, neutron and electrons
iv. Atoms of different elements may chemically combine in many different ratio to form compounds
3. J.J.THOMSON (1897)
He discover the Electron among the three sub-atomic particles
According to him atom is a sphere of positive charge, with negative particles called electrons spread throughout
the sp here.
This model was referred to as plum pudding model
Figure showing J.J. Thomson plum pudding model
Page2
YOU CAN NEVER BACK TIME USE IT………………… 0621952008
, PREPARED BY SIR PAUL KATIMKA 0621952008
4. ERNEST RUTHERFORD (1917)
He discover the second sub-atomic particle called proton
Rutherford develop model of atom called planetary model
ASSUMPTION RUTHERFORDS ATOMIC MODEL
i. Protons, the positively charged particles in atom, are located in the nucleus
ii. Most of the mass of the atom is located in the nucleus.
iii. The nucleus has relatively smaller volume compared to the whole atom
iv. Electron have very small masses compared to the protons
v. Most of the space in an atom is empty
vi. Electrons are the negatively charged particle in an atom. They move around the nucleus in orbits
Rutherford’s planetary model of the atom
5. JAMES CHADWICK (1932)
He discovered the neutrons which is the third sub-atomic in an atom.
Neutrons are located in the nucleus of an atom
THE PROPERTIES OF NEUTRONS
i. They have no charge (They are neutral)
ii. They have nearly the same mass as the corresponding protons
iii. They have a mass nearly 1840 times the mass of an electron.
Location of sub-atomic particles in the atoms
SUMMARY OF THE PROPERTIES OF SUB-ATOMIC PARTICLES OF AN ATOM
Sub-atomic Symbol Location Charg Real mass Relative
particles e (g) mass
-24
Protons P In the nucleus +1 1.6726×10 1
Neutron N In the nucleus 0 1.6750 × 10 - 1
24
Electron E Outside the -1 9.109 × 10 -28
nucleus
Page3
YOU CAN NEVER BACK TIME USE IT………………… 0621952008
, PREPARED BY SIR PAUL KATIMKA 0621952008
6. NIELS BOHR (1913)
He suggested that electrons rotate around the nucleus in special regions called shells or orbits or energy levels
Each shell can only hold a specific number of electron
The maximum number of electrons held within each shell can determined by the formula 2n2, where „n’ is the
position of the shell from the nucleus
According to this formula,
First shell can hold ( electrons
Second shell can hold ( s
Third shell can hold (
Fourth shell can hold (
The first four shell are represented by the letter K, L, M and N respectively as shown in figure below
First four shells of an atom
NOTE
1. From the third shell atoms are more stable with 8 electrons even though can holds more than 8
2. First shell can hold maximum of 2 electron and if it has 2 electrons it is said to be full-filled
3. From the second shell if it contain 8 electrons it is said to be full-filled shell
4. Atom with full-filled outermost shell is said to be stable
5. Element with a maximum of 2 electrons in their outermost shells (first shell) are said to exhibit duplet state
6. Element with a maximum of 8 electrons in their outermost shell are said to exhibit octate state
ELECTRONIC CONFIGURATION
This is the arrangement of electrons in different shells in an atom
NOTE
Electronic configuration can be done by using diagram or number ratio
If diagram is used at the center (nucleus) number of protons and neutrons must be shown
Electronic configuration of some atoms using diagram
Page4
YOU CAN NEVER BACK TIME USE IT………………… 0621952008
