periodic classification of elements class 10 notes

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2. Periodic Classification Of Elements The Modern Periodic Table

4. ✓ The Modern Periodic Table was introduced by Henry Moseley ✓ During his time 92 elements were already discovered. ✓ Based on his X-ray study analysis , he concluded that

5. • Elements should be arranged based on their Atomic Number but not Atomic Mass • Therefore all the 92 elements were arranged in increasing order of their atomic number. • There were • 18 groups (Vertical column) • 7 periods ( Horizontal row)

6. Group 1- 12 – Metals Group 13-18 – Non Metals B,Si,Ge,As,Sb,Te,Po – Metalloids

7. • The elements present in one single group will all have same physical and chemical properties • Elements present in the same group will have same number of valence electrons. • Periodicity – Elements shows similar physical and chemical properties after certain gap is called as Periodicity .

8. Modern Periodic Law states that, "Properties of the elements are the periodic function of their atomic number”

9. Position of Elements in Modern Periodic Table Periodic Table has 18 vertical Columns called as GROUPS and 7 horizontal Rows called as PERIODS Importance of Group Number • Elements present in the same group will have same number of valence electrons • For example- Group 1 will have 1 valence electrons • Group 2 will have 2 valence electrons • And so on

11. Therefore groups signifies an outer shell electronic configuration Also number of shell increases as we go down the group Importance of Period Number Period number tells about the shell number present in last number of electrons

12. The number of elements in periods are based on how electrons are filled in various shells The maximum number of electrons that can be accommodated in a shell depends on the formula 2n2where n – number of given shell from the nucleus

13. For example K shell- 2× (1)2= 2 first period has 2 elements L shell- 2× (2)2= 8 second period has 8 elements 3rd ,4th,5th ,6th ,7thperiod will have 8,18,18,32,32 elements

14. The position of element in the periodic table tells about the Chemical Reactivity Valence Electrons determine the kind and number of bonds formed by an element.

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