Question
Sun February 26, 2012 By:

an atom of atomic no. 19...now please explain me how to find its group no,period no.is it a metal or non metal..valency...

Expert Reply
Sun February 26, 2012
First write the electronic configuration:
 
19X = 1s2, 2s2 p6, 3s2 p6, 4s1
 
Now, remember the trend of electronic configuration og Groups and Periods.
Group 1 elemets have ns1 electronic configuration, or Group 2 has ns2 electronic configuration.
 
So, the given element belongs to Group 1.
 
About Period: In Period 1, the heighest level is 1, i.e. K.
In 2 Period it is 2, or L
In 3 period, it is 3 or M....
 
So, in this case we have highest energy level is 4, so the element will be in the fourth period.
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