Group 15 (N, P etc.) - Physical Properties

Question 1

Nitrogen has 2 electrons (saturated) in its penultimate shell. In accordance with Hund’s rule, electronic configurations involving fully filled or exactly half filled orbitals are most stable. Nitrogen behaves as a noble element under ordinary conditions

Answer 1

…

Question 2

Metallic character increases as atomic number increases. N and P are purely non-metals. Sb and Bi are metals. Ar is a metalloid

Answer 2

…

Question 3

N and P combine with electropositive elements to form nitrides and phosphides. Nitrides are more stable than phosphides. Bi and Sb form alloys with other metals

Answer 3

…

Question 4

There is a gradual change in physical state of these elements under ordinary conditions. Nitrogen is a gas. Phosphorus, though a soft waxy solid, can readily pass into vapor state. Remaining elements are solids, are hard and possess metallic lustre

Answer 4

…

Question 5

Atomic radii increase on going down the group due to addition of new energy shells. They are smaller than group 14 due to increased effective nuclear charge

Answer 5

..

Question 6

Covalent radius considerably increases from N to P due to strong shielding effect of s and p electrons in inner shells. But from As to Bi, only small change is observed due to poor shielding effect of d and l or f electrons present in inner shells on valency electrons - this increases nuclear charge and reduces effect of addition of new energy shell to some extent

Answer 6

..

Question 7

Ionization energy decreases down the group due to increase in atomic size. However they are higher than group 14 because of increased nuclear charge, reduced atomic radii and stable half-filled configurations -> more difficult to remove electron

Answer 7

..

Question 8

Ionization energy of nitrogen very high due to its small size. N and P difference is high but differences between other consecutive members is small - due to less shielding effect of d-electrons in As and Sb, and f-electrons in Bi

Answer 8

…

Question 9

Successive ionization energies increase as expected. E1 P > As > Sb > Bi

Answer 9

…

Question 10

Electronegativity decreases gradually on descending the group from N to Bi. N is most electronegative and is a non-metal

Answer 10

..

Question 11

Density increases gradually on descending the group

Answer 11

..

Question 12

All elements except Bismuth show allotropy

Answer 12

..

Question 13

Nitrogen exists in two solid allotropic forms, alpha nitrogen with cubic crystalline structure and beta nitrogen with hexagonal crystalline structure

Answer 13

..

Question 14

Phosphorus exists in number of allotropic forms such as white, red, scarlet, alpha-black, beta-black and violet

Answer 14

..

Question 15

Arsenic is known in 3 allotropic forms - grey, yellow and black. Antimony in 3 forms- yellow, black and explosive

Answer 15

..

Question 16

Group 15 elements show catenation to a lesser extent than carbon because X-X bond strength is much lower than C-C bond.

Answer 16

…

Question 17

Phosphorus has maximum tendency for catenation. N-N single bond is weak due to electronic repulsions between the lone pair of electrons on N atoms

Answer 17

..

Question 18

Nitrogen is diatomic gaseous molecule at ordinary temperature - this is due to its ability to form multiple bonds - the molecule has 1 sigma and 2 pi bond.

Answer 18

…

Question 19

Triple bond in N molecule is very stable and dissociation energy is very high - 225 kcal/mol. It is therefore inert under ordinary conditions

Answer 19

..

Question 20

Phosphorus, arsenic and antimony exist as discrete tetraatomic tetrahedral molecules P4, As4, Sb4. Not capable of forming multiple bonds, angle between X-X-X is 60 and p-pi-p-pi bonding not possible

Answer 20

..

Question 21

Bismuth involves purely metallic bonding

Answer 21

..

Question 22

Maximum oxidation state of +5 by using all 5 electrons in outer shell

Answer 22

..

Question 23

Tendency of the pair of ns electrons to remain inert (inert pair effect) increases with increase in atomic number. Thus only p electrons are used in bonding and +3 oxidation state is observed

Answer 23

….

Question 24

+3 and +5 oxidation states of these elements are observed with halogens and sulphur

Answer 24

..

Question 25

Stability of +3 increases and that of +5 decreases on moving down from N to Bi

Answer 25

..

Question 26

N and P exhibit -3 oxidation state due to high electronegativity and small size. N forms N3- Nitride ion with highly electropositive elements. P forms P3- Phosphide ion to some extent. Tendency to show -3 oxidation state decreases from N to Bi (decreases from As to Bi due to inert pair effect as stability of +3 state increases from As to Bi)

Answer 26

..

Question 27

Nitrogen exhibits large number of oxidation states from -3 to +5. -3 in NH3, -2 in NH2NH2, -1 in NH2OH, +2 in NO, +3 in N2O3, +4 in NO2, +5 in HNO3 and N2O5

Answer 27

..

Question 28

All oxidation states of Nitrogen from +1 to +4 show disproportionation in acidic medium (redox reaction - Disproportionation is a specific type of redox reaction in which a species is simultaneously reduced and oxidised to form two different products). 3HNO2 (+3) ->HNO3 (+5) +2 NO (+2) + H2O

Answer 28

..

Question 29

Phosphorus exhibits disproportionation in all intermediate oxidation states from -3 to +5 in acidic and basic mediums

Answer 29

..

Question 30

Nitrogen forms trinegative ion M3-. It can achieve stable configuration by forming 3 single covalent bonds, by forming double or triple bonds, by tricovalent N as lewis base, and forming certain N compounds where valence shell is not complete but compounds are stable - NO, NO2 etc. These have unpaired electrons, are para-magnetic and have tendency to dimerise

Answer 30

..

Question 31

Phosphorus attain stable configuration by sharing 3 p electrons and forming 3 covalent bonds..

Answer 31

..

Question 32

Nitrogen never shows pentavalency. Max covalency of 4 when it donates the ns-electron pair to lewis acids and it doesnt possess d-orbitals in valence shell. Other elements have empty d-orbitals and can show covalency of 5 or 6 - PCl5, SbF6- etc.

Answer 32

..

Question 33

N forms p-pi-p-pi multiple bonds with itself and with carbon and oxygen. Easily exists as triply bonded diatomic gaseous molecule at ordinary temp

Answer 33

..

Question 34

P can form p-pi-d-pi but does not form many compounds like N (P2O, P2O3 etc. do not exist) as it cannot form p-pi-p-pi

Answer 34

…

Question 35

P2O3 and P2O5 are known as dimeric oxides in the form P4O6 and P4O10

Answer 35

..

Question 36

Thermal and electrical conductivity increases down the group. N and P are poor conductor, As is a semi conductor. Sb and Bi are good conductors

Answer 36

..

Question 37

N forms 75% by mass and 78% by volume of atmosphere

Answer 37

..

Question 38

P doesnt occur free in nature - 11th most abundant element. 60% of bones are Ca3(PO4)2 and average person has 3.5 kg of calcium phosphate. Present in DNA, RNA, ATP, ADP etc. and also found as phosphates in nature

Answer 38

…

Question 39

As, Sb and Bi are not abundant. They occur as sulphides or oxides

Answer 39

..