A) why does the second line of the periodic table contain 8 entries? B) why are
ID: 872963 • Letter: A
Question
A) why does the second line of the periodic table contain 8 entries?B) why are the left hand parts of this line valence positive and the right hand parts valence negative?
C) Why is the position of lithium in the periodic table directly below that of hydrogen? A) why does the second line of the periodic table contain 8 entries?
B) why are the left hand parts of this line valence positive and the right hand parts valence negative?
C) Why is the position of lithium in the periodic table directly below that of hydrogen? A) why does the second line of the periodic table contain 8 entries?
B) why are the left hand parts of this line valence positive and the right hand parts valence negative?
C) Why is the position of lithium in the periodic table directly below that of hydrogen?
B) why are the left hand parts of this line valence positive and the right hand parts valence negative?
C) Why is the position of lithium in the periodic table directly below that of hydrogen?
Explanation / Answer
a)According to the Aufbau principle, the order of filling up of the various atomic orbitals in an atom is
1s
2s 2p
3s 3p
4s 3d 4p Note the reversal in the order of 3d orbital
5s 4d 5p Note the reversal in the order 4d orbital
6s 4f 5d 6s Note the reversal in the order of 4f and 5d orbitals
7s 5f 6d 7s Note the reversal in the order of 5f and 6d orbitals
There are 7 rows and these 7 rows correspond to the seven periods in the periodic table.
The Maximum number of electrons that can be accommodated in various atomic orbitals is as follows.
s- orbital 2
p- orbital 6
d- orbital 10
f- orbital 14
The elements of the second period have only s and p orbitals (2s and 2p) .So the maximum number of elements in the second period is 2(s-orbital) + 6(p-orbital) = 8
Hence the second period contains eight entries/elements
b) Elements with a tendency to lose elecrons to form positive ions (cations) are said to be electro positive
Elements with a tendency to gain elecrons to form negative ions (anions) are said to be electro negative
Elements with 1,2 and 3 electrons in the outer most orbitals will have a tendency to lose electrons to achieve stable octet configuration. Hence these elements are electro positive
On the other hand, Elements with 5,6 and 7 electrons in the outer most orbitals will have a tendency to gain electrons to achieve stable octet configuration. Hence these elements are electro negative.
On the left hand side of the periodic table we have elements with 1,2 or 3 electrons and on the right hand side of the periodic table we have elements with 5,6 or 7 electrons (confirm this by writing the electronic configurations of elements) .Hence the elements on the left hand side of the periodic table have positive valence and the elements on the lright hand side of the periodic table have negative valence.
c) Atomic number of H = 1 Electronic configuration of H is 1s1
Atomic number of Li = 3 Electronic configuration of Li is 1s2 2s1
Both H and Li have the same configuration in the valence shell (outer most orbital) .So they are placed in the same group namely first group (or IA) in the periodic table
H with 1s1 configuration is in the first period and Li with 2s1 configuration is in the second period immediately below H
ADDITIONAL VERY USEFUL TIPS:
Learn the table by heart.
Using this table ,you can answer question like
What are the variuos atomic orbitals filled up in the 4th period and what is the order? and similar questions
What is the number of elements in the 6th period ? and similar questions
Also you can write the the electronic configuration of any elelment in the periodic table with effortles ease.
For that, you write the orbitals in the given order ( 1s 2s2p 3s3p 4s3d4p.......) as VACANT ORBITALS AND THEN FILL THEM UP with electrons. Never Start writing 1s2 2s2 and so on strightaway.
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