Modern Periodic Law and Modern Periodic Table
Moseley in 1913, after doing many experiments comes to a conclusion that the elements should be arranged as per their atomic no. and not according to atomic masses. As atomic no. is fundamental property of all elements of periodic table. So Mosley gives a new law which is called is Modern Periodic Law.
Modern Periodic Law
According to Modern Periodic Law- “Physical and Chemical properties of elements are periodic function of their atomic numbers”.
Long Form of Periodic Table
Bohr Bury invented new periodic table, which is called as Long Form of Periodic Table. This Long Form of Periodic Table is also known as Modern Periodic Table.
Special features of Modern or Long Form of Periodic Table
These below are Special features of Modern or Long Form of Periodic Table
1. 18 vertical columns known as groups.
2. Horizontal rows known as periods.
3. Light metals – These are elements of periodic table of group 1 and 2.
4. Heavy metals or Transition metals - These are elements of periodic table of group 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12.
5. Non-Metals – These are elements of periodic table of group 13, 14, 15, 16 and 17.
6. Zero group – These are elements of periodic table of group 18.
Properties of periods
1. All periods start with alkali metal and end with noble gases.
2. If we see table, it is very clear that from 1st to 7th period there is an addition of one shell in the each period like n=1,2,3,4,5………………
Properties of groups
1. In any group, outermost shell electron are known as valance electrons and these electrons are same so main properties of elements of group is similar.
2. Elements are divided into four blocks, which is s, p, d, f according to valance electrons.
3. s-block elements – elements of 1 and 2 group.
4. p-block elements – elements of 13 to 18 group.
5. d-block elements – elements of 3 to 12 group.
6. f-block elements – elements of the Lanthanide and Actinide series.
7. Representative Elements – elements of s-block and p-block collectively called as Representative elements also known as Normal elements or Typical elements.
8. Transition Elements – elements of d-block.
9. Inner Transition Elements – elements of f-block, also known as Rare Earth Elements.
10. Alkali Metals – elements of 1st group.
11. Alkaline Earth Metals – elements of 2nd group.
Solution for the demerits of Mendeleev’s Periodic Table in the Long Form of Periodic Table (or Modern Periodic Table)
1. Mendeleev’s Periodic Table contains some heavy elements placed before lighter elements, this problem is solved automatically in Modern Periodic Table
2. All isotopes of an element have same atomic number so no need to place them separate.
3. All inert gases (or noble gases) got their appropriate place in zero group (or 18th group).
4. Mendeleev’s Periodic Table have problem with 8th group but it is resolved in Modern Periodic Table as it is divided into three groups.
Drawback of Modern Periodic Table
1. Position of Hydrogen is still not clear in Modern Periodic Table.
2. Position of f-block elements (Lanthanides and Actinides) is not proper as these placed at bottom, separately from periodic table that is impractical.