The Periodic Law

The Henry Gwyn JeffreysMoseley (Henry G.J Moseley) 

The Henry Gwyn Jeffreys Moseley was an English Scientist (physicist), and his contribution to the science (physics) is the Concept of the atomic Number, where he proved it and also the Niels Bohr's atomic theory  was the first experimental proof (evidence) in his favour along with the Ernest Rutherford theory and the Antonius van den Broek theory.This on this basis he proposed a law called Moseley's law in x - ray spectra.

In 1913 Henry Moseley came to know that the properties of elements depends on their atomic number not on the atomic masses number. The Henry Moseley observed that the properties of elements are repeated in a regular manner when they are arranged in increasing order of atomic number i-e the elements of same properties are placed in the same group. On this basis he proposed law known as a Periodic Law or Moseley's law.

The Moseley's Law or The Periodic Law: This law states that “the physical and chemical properties of an element are the periodic functions of their atomic number”.

Hence modern periodic law started and new era of classification started and scientist observed that the errors of all elements will remove with this law when they are arranged in increasing order of their atomic number.Thus the previous laws were rejected and the new law discovered the new arrangement of elements called modern periodic table The modern periodic table has 18 vertical columns known as groups and 7 horizontal rows known as period.

The Periods in Periodic table: The seven horizontal particular rows of elements in modern periodic table known as period. There are seven periods in modern periodic table.

1 - First Periods (n=1): Here n indicates there is only one main shell for the elements of this period and there are only two elements in this period.

2 - Second Periods (n=2): There are only two shells for the elements of this period and there are 8 elements in this period.

3 - Third Periods (n=3): There are only three shells for the elements of this period and there are 8 elements in this period.

4 - Fourth Periods (n=4): There are only four shells for the elements of this period and there are 18 elements in this period.

5 - Fifth Periods (n=5): There are only five shells for the elements of this period and there are 18 elements in this period.

6 - Sixth Periods (n=6): There are only six shells for the elements of this period and there are 32 elements in this period.


7 - Seventh Periods (n=7): There are only seven shells for the elements of this period and there are 26 elements in this periods but this period is incomplete.

The Groups in Periodic table: The vertical particular column of elements in modern periodic table is called groups. There are 18 groups in periodic table.

The elements in a group have similar electron configuration due to due to same number of electron in their last or outermost shell. That’s why the elements in the group have similar chemical properties. Some groups are also called by their specific name known as family name.

• First Group (Alkali Metals): This group element possesses +1 charge.
• Second Group (Alkaline Metals): This group element possesses +2 charges.
• Third Group (Boron Family): This group element possesses +3 charges.
• Fourth Group (Carbon family): This group elements possess +4 – 4 charges.
• Fifteenth Group (Nitrogen Family): This group element possesses –3 charges.
• Sixteenth Group (Oxygen Family): This group element possesses –2 charges.
• Seventeenth Group (Halogens means salt producer): This group elements possess – 1 charge.
• Eighteenth Group (Noble gases): This group element possesses 0 charges and is neutral.

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• Learn about Niels Bohr's Atomic theory/model

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