s and p

Question 1

why are they called s block elements

Answer 1

valence electrons present in s block

Question 2

why they called p block elements

Answer 2

group 3a to 8a elements except helium.
valence electrons in p block

Question 3

f block elements

Answer 3

lanthanides and actinides. valence e in f block

Question 4

Classification of elements in blocks is based on the:

A.Ease of removal of electron

B.Ease of gain electron

C.Number of electrons present in the valence shell

D.Valence orbital of the element involved in chemical bonding

Answer 4

D.

Classification of elements in blocks is based on the valence orbitals of the elements involved in chemical bonding. Elements are classified into four blocks: i. s-block ii. P-block iii. d-block iv. f-block

Question 5

assumptiions for measuring atomic size.

Answer 5

1. atoms assumed as spherical
   2.size of atoms expressed in terms of atomic,ionic and covalent radii

Question 6

Methods of measuring atomic radius

Answer 6

distance bw centres of adjacent atoms by
. xrays
.spectroscopy
.electron diffraction

Question 7

why cant atomic radius be determined precisely

Answer 7

1. no sharp boundary of an tom.
   2.electronic probability distribution is affected by neighbouring atoms.

Question 8

atomic radii trend

Answer 8

1.decreases from left to right in a period.
due to;
increase in nuclear charge
sheilding remains same from left to right

2.increases from top to bottom
due tp;
increase in shells
increased shielding

Question 9

ionic radii (cationic and anionic)

Answer 9

1. catonic radius smaller than parent atom.
   .shell may be removed
   .eff nuclear charge increases

2.anionic radii larger than parent (cl to cl-)
.atom expands its valence shell

Question 10

isoelectronic species

Answer 10

cations of any period have similar number of electrons(are isoelectronic to each other)

similarly anions do this too(also isolelectronic to noble gases)

Question 11

covalent radii trend

Answer 11

left to right decreaase
top to bottom increase
(almost same as atomic radi)

Question 12

ionisation energy

Answer 12

min energy req to remove an electron from its gaseous atom to form ion

Question 13

ionisation energy trends

Answer 13

along the group
.decreases top to bottom

along the period
increases from left to right

Question 14

factors affecting ionisation energies(4)

Answer 14

1. I.E inersely propotional to atomic radius
2. I.E directly propotional to nuclear charge
3. I.E inverse with sheilding
4. penetration effect direct relation with I.E

Question 15

sheilding effect across the period?

Answer 15

remains constant.
(down the group becomes stronger. along the period has same shell)

Question 16

reverse of ionisation energy process is called

Answer 16

electron affinity

Question 17

which group of elements have the highest I.E

Answer 17

group VIIIA or noble gases

Question 18

electron affinity

Answer 18

energy released when an electron adds to empty or half filled orbital of a gas atom to form an anion 1- ion.

first ea always exo -
second always endo +

Question 19

trends of e.a

Answer 19

decreases down the group
increases left to right

Question 20

why fluorine’s E.A is less than that of chlorines

Answer 20

F2 is small and have 7 electrons in 2s and 2p subshells which have a thick electron cloud(which repels incoming electrons.)

Question 21

which groups have abnormal trend of E.A(low ea) in every peroid

Answer 21

group 2a, 5a and 8a.(hence, halogens have highest ea)

(2a)metals love to lose e- not gain
(5a) have half filled p shell
(8a) have filled valence shell.[doesnt need.]

Question 22

bond formed bw elements of low i.e and high e.a.

Answer 22

ionic.

low i.e=metals
high ea=non metals.

Question 23

electronegativity

Answer 23

tendency of an atom to ATTRACT A SHARED ELECTRON PAIR to itself.

Question 24

electron affinity trends with reasons

Answer 24

1. decreases down the group
   (increase in atomic size and sheilding efect)

2.increases from left to right
(decrease in atomic size and sheilding constant)

Question 25

E.N difference= nature

Answer 25

if EN diff> 1.7 = BOND IS IONIC

if EN diff<1.7 and >0.5= POLAR COVALENT

EN<0.5 =NON POLAR COVALENT

EN=1.7 = BOTH IONIC AND COVALENT CHARACTER

Question 26

element having i.e_____ and E.A_______would be most electronegative

Answer 26

high and high.
left to right both increase.

Question 27

m.p and boiling point trends group 1a and 2a

Answer 27

decreases from top to bottom
due to increase in atomic size
and metallic bond weakens.

Question 28

M.P trends group (3a-4a)

Answer 28

decreases top to bottom

Question 29

M.p and B.p trends (group 5a-7a)

Answer 29

increase from top to bottom due to;
molecules being small
increase in size
polarizability increases
attractive forces increase

Question 30

variation of m.p and b.p left to right

Answer 30

both increase up to group 4a then decreases going to 6a

Question 31

group 2 elements reaction with oxygen

Answer 31

berellium at 800 degree

Magnesium burns with dazzling white light

Calcium brick red flame

strontium bright red

barium apple green

Question 32

group 2 elements reaction with water

Answer 32

berillium inreactive

magnesium with hot water to give H2

calcium sinks in cold water to give H2

strontium and barium vigourous reaction forming soluble hydroxides

Question 33

G2 reaction with nitrogen

Answer 33

form nitrides “M3N2”.

hydrolysis produce ammonia

Question 34

Group 3 elements with water

Answer 34

Boron only with steam gives B2O

Aluminium doesnt due to protective oxide layer (corrosion free)

Thalium [Tl] forms thalium hydroxide

Question 35

Group 3 with oxygen

Answer 35

all reactive at high temp to produce trioxides. {M2O3}

Boron reacts in amorphous form

Al forms a stable layer of Al2O3 acts as protective layer at 800 degree.{used for flashlight photgraphy}

Question 36

group 3a with Chlorine

Answer 36

high temperature required to form Trihalides MX3

Boron forms covalent liq boron trichloride on heating

Al burns when heated strongly in chlorine gas

thalliumonly forms TlF3 and TlCl3

Question 37

ionisation energyy is the index of metallic character meaning

Answer 37

atoms with low ie are metals, intermediate are metalloid and high I.E are Non-metals

Question 38

i.e and e.a main differnce

Answer 38

e.a is the ADDITION OF e-

i.e is the REOMVAL of e-