### JEE Mains Previous Years Questions with Solutions

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### JEE Main 2013 (Offline)

Which of the following represents the correct order of increasing first ionization enthalpy for Ca, Ba, S, Se and Ar?
A
S < Se < Ca < Ba < Ar
B
Ba < Ca < Se < S < Ar
C
Ca < Ba < S < Se < Ar
D
Ca < S < Ba < Se < Ar

## Explanation

Those elements are present in periodic table like this -

Group 2 Group 16 Group 18
Period 3 Ca .......... S ......... Ar
Period 4 Sc
Period 5 Ba

In periodic table,

1. From left to right ionization energy increases.

2. From top to bottom ionization energy decreases.

$\therefore$ Ba < Ca and Se < S and S < Ar

$\therefore$ Correct order is -
Ba < Ca < Sc < S < Ar
2

### AIEEE 2012

The increasing order of the ionic radii of the given isoelectronic species is :
A
Clâ€“, Ca2+ , K+ , S2â€“
B
S2â€“, Clâ€“, Ca2+ , K+
C
Ca2+ , K+ , Clâ€“ , S2â€“
D
K+, S2â€“, Ca2+, Clâ€“
3

### AIEEE 2011

Outer electronic configuration of Gd (Atomic no : 64) is -
A
4f85d06s2
B
4f45d46s2
C
4f75d16s2
D
4f35d56s2

## Explanation

Electronic configuration of Gd(64) : [Xe]4f75s25p65d16s2

So the outer electronic configuration will be : 4f75d16s2

Shortcut Method : Gd belongs to 4f series which is also called lanthanide series. In this lanthanide series for Cerium (Ce), Gadolinium (Gd) and Lutetium (Lu) outer d orbital has 1 electron and for all other lanthanide series elements outer d orbital has 0 electron. From this you can easily say option (C) is correct.
4

### AIEEE 2011

Which one of the following order represents the correct sequence of the increasing basic nature of the given oxides ?
A
MgO < K2O < Al2O3 < Na2O
B
Al2O3 < MgO < Na2O < K2O
C
Na2O < K2O < MgO < Al2O3
D
K2O < Na2O < Al2O3 < MgO

## Explanation

You should know that,

(1)$\,\,\,$ In a period, from left to right the acidic strength increases that mean basic nature decreases.

(2)$\,\,\,$ In a group, from top to bottom the basic nature increases that means acidic nature decreases.

Na, Mg, Al and K are present in periodic table like this : -

Group 1 Group 2 Group 13
Period 3 Na Mg ..... Al
Period 4 K

So, you can see Na, Mg and Al are present in same period so the order of basic nature among Na, Mg and Al is Na > Mg > Al.

And Na and K are from same group so basic nature of K > Na.

So the correct order of oxides

Al2O3 < MgO < Na2O < K2O