elements and its arrangement in modern periodic table in these slides are well defined you can follow me on my you tube channel

1. Follow on Youtube channel name is (M Ramzan
Educational Point)
https://www.youtube.com/watch?v=CwPefarsRH0M.Ramzan (M.Sc Chemistry)

2. Old Definition
“Element is a substance that can
not be broken down into simpler units
by ordinary chemical process.”
Element
M.Ramzan (M.Sc Chemistry)

3. In past only nine elements were known at
that time.
These were carbon, gold, silver, tin,
mercury, lead, copper, iron and sulphur.
M.Ramzan (M.Sc Chemistry)

4. “It is a substance made up of same type of
atoms, having same atomic number and cannot be
decomposed into simple substance by ordinary
chemical means.”
M.Ramzan (M.Sc Chemistry)

5. At the end of nineteenth century only 63 elements
were discovered.
Now 118 elements have been discovered, out of
which 92 are naturally occurring.
M.Ramzan (M.Sc Chemistry)

6. Elements occurs in free or combined both
states.
In nature elements are present in earth’s crust,
ocean and air.
Natural occurrence by weight % of some major elements is given
below
Earth’s Crust Ocean Atmosphere
Oxygen 47% Oxygen 86% Nitrogen 78%
Silicon 28% Hydrogen 11% Oxygen 21%
Aluminium 7.8% Chlorine 1.8% Argon 0.9%
M.Ramzan (M.Sc Chemistry)

7. Elements may be solid, liquid and gas.
80% elements exist as solid such as gold, silver,
copper, zinc, carbon etc.
Mercury and bromine exist as liquid.
A few elements exist as gases such as
nitrogen, oxygen, chlorine and hydrogen.
M.Ramzan (M.Sc Chemistry)

8. Elements are also classified as Metals, Non-metals and Metalloids.
Metals:
“An element which is good conductor of heat and electricity,
malleable and ductile, has a shiny surface and always forms positive
ions by losing electrons is called Metal.” 80% elements are metals.
Examples: sodium, copper, silver, gold, iron etc.
M.Ramzan (M.Sc Chemistry)

9. Non-Metals:
“An element which is non conductor of heat and
electricity, not malleabe and not ductile, not lustrous and
always forms negative ion by gaining electrons is called Non-
Metal. Example: Carbon, sulphur, phosphorus, fluorine,
chlorine etc.

10. Metalloids:
“An element having physical and chemical properties of
both metals and non-metals is called Metalloid.”
Example: only seven elements are metalloids. They are boron,
silicon, germanium, antimony, tellurium and astatine.
M.Ramzan (M.Sc Chemistry)

11. “Two or more atoms of an element having
the same atomic number but different mass
numbers are called isotopes.”

12. Isotopes of Carbon
 Carbon has three isotopes
 Carbon -12 ( 𝟔
𝟏𝟐
𝑪) ,carbon-13( 𝟔
𝟏𝟑
𝑪) and carbon-14 ( 𝟔
𝟏𝟒
𝑪 ). Carbon 14 is
radioactive.

13. Modern Periodic Law
In 1913, H. Moseley discovered a new property
of the elements which is atomic number.
Atomic number is more fundamental property
than atomic mass because atomic number of an
elements is fixed.
All isotopes have the same atomic number.
Also no two elements can have the same atomic
number.

14. Modern periodic law can be stated as:
“The properties of elements are periodic
function of their atomic numbers.”

15. Modern Periodic Table
The basis of classification of
elements in the modern periodic table
is atomic number and modern periodic
law.

16. Modern Periodic Table
Atomic number of an elements is more fundamental
property than atomic mass in two respects.
1. It increases regularly from element to element.
2. It is fixed for every element and its isotopes. Different
atoms of the same element have the same atomic
number.

18. Electronic configuration
“The distribution of electrons in various
subshells according to their increasing energy is
called electronic configuration.”

19. In filling the subshells electrons enter in lower energy subshell first.
The increasing order in which the electrons will enter into subshells is;
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s,
4f, 5d, 6p, 7s
 The filling of subshells can be represented as follows.
“n” 1 2 3 4
Shells/ Energy
Level
K L M N

20. Maximum number of electron in any
shell
 Maximum number of electrons in any shell can be calculated by formula
2n2
 For K n=1, the number of electrons in K shell = 2n2 = 2(1)2 = 2
 For L n=2, the number of electrons in L shell = 2n2 = 2(2)2 = 8
 For M n=3, the number of electrons in M shell =2n2 = 2(3)2 = 18
 For N n=4, the number of electrons in N shell = 2n2 = 2(4)2 = 32

21. Number of Subshells in a shell
“n” Shell Subshell
1 K “s”
2 L “s , p”
3 M “s, p, d “
4 N “s, p, d, f “
M. Ramzan (M.Sc. Chemistry)

22. Maximum number of electron in a
subshells
 “s” subshells can accommodate a maximum of 2 electrons.
 “p” subshells can accommodate a maximum of 6 electrons.
 “d” subshells can accommodate a maximum of 10 electrons.
 “f” subshells can accommodate maximum of 14 electrons.
M. Ramzan (M.Sc. Chemistry)

23. Examples
1H = 1s1
2He = 1s2
3Li = 1s2 , 2s1
4Be = 1s2 , 2s2
5B = 1s2 , 2s2 , 2p1
6C = 1s2 , 2s2, 2p2
7N = 1s2 , 2s2, 2p3
8O = 1s2 , 2s2, 2p4
9F = 1s2 , 2s2, 2p5
10Ne = 1s2 , 2s2, 2p6
11Na = 1s2 , 2s2, 2p6 , 3s1
12Mg = 1s2 , 2s2 , 2p6 , 3s2
13Al = 1s2 , 2s2 , 2p6 , 3s2 , 3p1
14Si = 1s2 , 2s2 , 2p6 , 3s2 , 3p2
15P = 1s2 , 2s2 , 2p6 , 3s2 , 3p3
16S = 1s2 , 2s2 , 2p6 , 3s2 , 3p4
17Cl = 1s2 , 2s2 , 2p6 , 3s2 , 3p5
18Ar = 1s2 , 2s2 , 2p6 , 3s2 , 3p6
19K = 1s2 , 2s2 , 2p6 , 3s2 , 3p6 , 4s1
20Ca = 1s2 , 2s2 , 2p6 , 3s2 , 3p6 , 4s2

24. Thanks
M.Ramzan (M.Sc Chemistry)