Periodicity

Question 1

nuclear charge

Answer 1

Total charge of all protons in nucleus. larger the no. of protons, greater the nuclear charge

across period/down group nuclear charge increases

Question 2

Shielding effect

Answer 2

the repulsion valence electrons feel from inner shell electrons apart from attraction to protons in nucleus
increase with increasing no. of inner shell electrons (PSQ)/size of atom

increases down group, relatively same across period due to same number of inner shell electrons

Question 3

Nuclear attraction

Answer 3

net attraction for valence electron

nuclear charge - shielding effect + distance of valence electrons from nucleus

Question 4

distance of valence electrons away from nucleus

Answer 4

larger the no. of filled electronic shells, further the valence electrons are from the nucleus weaker the nuclear attraction

Question 5

Atomic radii

Answer 5

Covalent radius
Metallic radius
van der Waals radius

Question 6

Covalent radius

Answer 6

1/2 the internuclei distance between 2 atoms that are covalently bonded

covalent bond length= sum of the 2 covalent radii

Question 7

Metallic radius

Answer 7

1/2 the internuclei distance between two adjacent metal atoms in a metallic lattice

Question 8

van der Waals radius

Answer 8

for noble gases that are inert and do not form covalent bonds with one another. are a different form of measurement of internuclei radius from covalent and metallic

Question 9

Trends across the period

Answer 9

1. Atomic radius decreases
2. Ionic radius decreases
3. Electronegativity increases
4. Ionisation energy increases

Question 10

Atomic radius

Answer 10

across the period
1. Nuclear charge increases due to increasing proton no.
2. shielding effect remans relatively constant due to same no.of inner shell electrons
3.

Question 11

Ionic radius

Answer 11

NSND across isoelectronic species

I.E of anionic series has a sharp increase from cationic series as anions have n more electron filled PQS than cations as they gained electrons

lesser nuclear charge, nuclear attraction, valence electrons further away from nucleus

Question 12

Electronegativity

Answer 12

NSND + hence increasing nuclear att. on shared bonding pair of electrons in covalent bond hence increasing electronegativity

Question 13

Ionisation energy

Answer 13

NSND + hence greater energy required to remove most loosely held valence electron hence increasing I.E

Question 14

Exceptions to I.E.

Answer 14

1. Small dip in I.E from group 12 to group 13 (Al and Mg)
   WHY?
2. Small dip in I.E from group 15 to 16 (P and S)
   WHY?

Question 15

Trends down the group

Answer 15

1. Atomic radius increases
2. Ionic radius increases
3. Electronegativity decreases
4. Ionisation energy decreases

Question 16

Atomic radius + Ionic radius

Answer 16

1. Number of PQS increases down the group by n
2. Increase in no.of inner shell electrons that increases shielding effect
3. These factors outweigh increase in nuclear charge due to increasing proton number
4. Distance of valence electrons from nucleus is further valence electrons experience lesser nuclear attraction , valence electrons less attracted to nucleus hence radius increases

Question 17

Electronegativity + I.E

Answer 17

1. Number of PQS increases down the group by n
2. Increase in no.of inner shell electrons that increases shielding effect
3. These factors outweigh increase in nuclear charge due to increasing proton number
4. Distance of valence electrons from nucleus is further valence electrons experience lesser nuclear attraction , valence electrons less attracted to nucleus

• less energy required to remove 1 mole of most loosely held valence electron from atom/ion hence IE decreases
• lesser nuclear att. for shared bonding pair of electrons in covalent bond hence decreasing electronegativity

Question 18

I.E

Answer 18

1st I.E value is lowest for for grp 1 since electron is removed from valence PQS

2nd I.E value lowest for grp 2 and so on