across period 3

Question 1

atomic radius

Answer 1

decreases.
(no of protons increase, nuclear charge increase. shielding effect remain relatively constant. effective nuclear charge increases, stronger electrostatic forces of attraction between nucleus and valence electrons.) valence electrons closer to nucleus.

Question 2

Ionic radius [1]

Answer 2

anions larger than cations. anions have one more electron shell, greater shielding effect. valence electrons e less strongly attracted.

Question 3

ionic radius [2]

Answer 3

ionic radius decreases with atomic number. isoelectronic. proton no increase, nuclear charge increase. valence electrons more strongly attracted.

Question 4

1st IE

Answer 4

generally increses. (same). more energy needed to remove

Question 5

1st IE [anomaly1: Al<Mg ]

Answer 5

Al: 3s2 3p1
Mg: 3s2
3p e to be removed from Al at higher energy level than 3s e from Mg. lesser energy required to remove valence e from Al.

Question 6

1st IE [anomaly 2: S<P]

Answer 6

S: 3p3
P: 3p4
inter e repulsion btwn paired e in S atom, less energy needed to remove

Question 7

electronegativity

Answer 7

increase in electronegativity across the period (same)

Question 8

melting pt [Na-Al]

Answer 8

high mp.
giant metallic structure, strong metallic bonds (electrostatic forces of attraction btwn cations and sea of delocalised e). large amts of energy required to overcome.

mp increases
increase in bond strength
increase in no of valence e contributed (1 to 3)
increase in charge density

Question 9

mp [Si]

Answer 9

highest mp
giant molecular structure. Si atoms held by strong and extensive covalent bonds in a giant 3d molecular structure. large amts of energy required to break.

Question 10

mp [P to Ar]

Answer 10

S> P> Cl> Ar
simple molecular structure
held tgt by weak idid
- size of e cloud increases
- distortion of e cloud more
- extent of idid more
-more energy required to overcome
small amts of energy to overcome

Question 11

electrical conductivity [Na-Al]

Answer 11

high electrical conductivity
increase from Na to Al
prescence of delocalised e, act as mobile charge carriers
no of delocalised e/atom increases (1-3)

Question 12

electrical conductivity [Si]

Answer 12

silicon semiconductor

Question 13

electrical conductivity [P to Ar]

Answer 13

abscence of delocalised e and mobile ions to conduct electricity

Question 14

OA oxide & chloride

Answer 14

oxidation no positive, less electronegative than O n Cl.

trend: increase in OA across period, max ON = no of valence electrons.

P&S: exhibit maximum O.S, central atom expanded octet (availability of energetically accessible n vacant 3d orbital)

Question 15

oxide mp/bp

Answer 15

(Mg>Na) giant ionic lattice, strong ionic bonds
magnitude of LE proportial to —
ionic charge ionic radius ionic bond strength energy needed
(Al) AL3+ high charge density, polaries O-, presence of covalent chracter, weaken bond strength
SiO2: same as Si exp
(P4O10>SO3) simple molecular structure, weak id-id, small amt of energy
P4O10 large e cloud size stronger idid, more energy needed to overcome

Question 16

oxides reactions w H2O

Answer 16

refer to table in notes
file:///home/chronos/u-f808d0d00490607388f06f5aec0b237e165a1025/MyFiles/Downloads/Screenshot%202025-02-21%2022.15.41.png

Question 17

acid base nature of oxides

Answer 17

Na,Mg: basic, rxt w acid to form salt and h2o
Al: amphoteric, rxt w both acid and base
- ionic w covalent character, Al3+ high charge density, polarise o2-, induce partial covalent character
- rxn with base forms __Al(OH)4 aq

hydroxides of these 3 have similar nature

Si,P,S: rxt w base, form salt & h2o
- SiO2(s) + 2NaOH(conc.)→ Na2SiO3(aq) + H2O(l) [requires hot concentrated NaOH]
- P4O10(s) + 12NaOH(aq)→ 4Na3PO4(aq) + 6H2O(l)
- SO3(g) + 2NaOH(aq)→ Na2SO4(aq) + H2O(l)