Classification of elements and periodicity in properties

Question 1

3d transition starts from which element to which element and what are their atomic numbers and EC’s

Answer 1

starts with scandium (Z=21; 3d14s2) and ends with Zinc (Z=30; 3d104s2)

Question 2

4d transition series starts from which element to which element + what r their atomic numbers and EC’s

Answer 2

starts with yttrium (Z=39; 4d1 5s2) and ends with cadmium

Question 3

what is the relationship between number of elements in each period and number of atomic orbitals available in the energy level?

Answer 3

the number of elements in each period is twice the number of atomic orbitals available in the energy level that is being filled.

Question 4

what are the 4f and 5f inner transition series’ called?

Answer 4

4f-lanthinoid; 5f-actinoid

Question 5

Justify presence of 18 elements in 5th period

Answer 5

when n=5, l=0,1,2,3. The order in which the energy of the available orbitals 4d, 5s, 5p increases is 5d<4d<5p. The total no of orbitals available are 9. thus the maximum number of electrons that can be accomodated is 18.

Question 6

S-block elements features

Answer 6

• outermost ec: ns^1-2
• reactive metals with low ionization enthalpies
• metallic character and reactivity increases down the group.
• never found pure in nature
  *strong reducing agents
• except Li and Be, others are predominantly ionic.

Question 7

P-block elements

Answer 7

*outermost ec: ns^2np^1-6
*metallic character increases downwards, non-metalic character increases left to right
*high electron gain enthalpy and ionisation energy-increase along a period-decrease down a group
*Oxidising character increases along a period; reducing character increase down a group

Question 8

Group 15-name

Answer 8

pnictogens

Question 9

group 16

Answer 9

chalcogens`

Question 10

group 17

Answer 10

halogens

Question 11

group 18

Answer 11

noble gases

Question 12

D-block elements

Answer 12

*putermost ec: n-1d^1-10ns^0-2
*all are metals
*very high melting and boiling points
*many form colored ions bcoz of presence of partially filled d-orbitals
*show paramagnetism, because of presence of unpaired e- in d orbitals
*used as catalysts

Question 13

f-block

Answer 13

*outermost ec: (n-2)f^1-14(n-1)d^0-1ns^2
*all are metals
*most common oxidation state is +2
*all actinoids are radioactive
*transuranium-elements following uraniu,-neptunium to Uub(Z=112)
*Th, Pa, cand U are only natural actinoids, rest are man-made

Question 14

which type of element has largest radius in its period?

Answer 14

noble gases-van der waal’s radius-since the van der waals firces are weak.

Question 15

ionisation enthalpy trend-group and period

Answer 15

period-increases from left to right; group-decreases moving down

Question 16

electron gain enthalpy

Answer 16

becomes more negative across a period and less negative down a group

Question 17

electronegativity

Answer 17

across a period-increases, down a group-decreases

Question 18

metallic character

Answer 18

across a period-decreases, down a group-increases