Chemical Periodicity

Question 1

what is periodicity

Answer 1

the recurrence of the same pattern

when moving across the period.

Question 2

periodic pattern of atomic radii AND why

Answer 2

Generally, the atomic radius decreases
moving across the period.
This is so due to increase in effective
nuclear charge from left to right and outer electron is in same principle quantum shell

Question 3

Periodic Patterns of ionic Radii

Answer 3

generally decrease but there is sharp increase between metal to non metal

Question 4

why do metal ions (cations) have small radi and nonmetals (anions) large

Answer 4

metals lose electrons, less shielding effect

non metals gain, increased repulsive force

Question 5

Periodic patterns of melting points and
electrical conductivity (p3)

Answer 5

increases moving across the period from sodium to aluminium
silicon (semimetal) has highest mp because its a giant structure of strong covalent bonds but low electrical conductivity due to no delocalized elctrons
rest are non metals with low mp due to weak van der waals forces and barely conduct electricity

Question 6

why does Al have high mp and electrical conductivity

Answer 6

mp:more electrostatic force between many electrons and cation
E:3+ ie 3 delocalized electrons per atom

Question 7

Periodic patterns of first Ionisation

energies

Answer 7

generally increase but some anomalies such as Al and S in pd3 because of electronic config ie Al

Question 8

Reaction of Period 3 Elements with

Chlorine

Answer 8

Na, Mg, Al react vigorously with chlorine gas.
Si and P react slowly with chlorine
no biproducts

Question 9

OXIDES OF PERIOD 3 ELEMENTS

Answer 9

react with oxygen to form oxides. na and mg is vigorous si is slow

Question 10

oxidation no is +/-? And why? Inc/dec across pd3…

Answer 10

is positive because oxygen has higher electronegativity than the pd3 elements

And increases till S across as each of the elements in its oxide can use all it’s outer shell electron in bonding to oxygen/chlorine

Question 11

what do oxides of pd3 react with water form

Answer 11

•Oxides of sodium and
magnesium with water
forms hydroxides of OH- ions(O2- ions behave as base and accept H+ from H2O)
•Al dissolves in acidic sol to form soluble salt (amphoteric)
•P and S dissolve to form acidic sol(donate H+ to h2o). P and S oxides are insol and dissolve JB alkali to form salt

Question 12

Na and Mg oxides are used in

Answer 12

indigestion medicine (basic so neutralise acid in stomach)

Question 13

nature of pd3 oxides

Answer 13

metals are basic
nonmetals acidic
Al is amphoteric

Question 14

meltint point trend of pd3 oxides

Answer 14

increases from sodium to silicon (giant oxide structure) then decreases to sulfur (simple molecular)

Question 15

use of MgO of high mp

Answer 15

line inside of furnaces

Question 16

use of SiO2 and Al2O3 of high mp

Answer 16

ceramics

Giant covalent structure withstand high temp and provide electrical insulation

Question 17

electric conductivity in liquid state of pd3 oxides trend

Answer 17

na to al increases bcos ionic bonding

si to s dont bcos covalent bonding (si is giant rest are simple mol)

Question 18

electronegativity trend across a pd

Answer 18

increases

Question 19

pd 3 chlorides have + oxi because

Answer 19

Cl has high EN

Question 20

Effect of water on Na and Mg chlorides

Answer 20

simply ionise. white solids dissolve to give colorless sol

Question 21

effect of water of Al2Cl6

Answer 21

acidic solution

Question 22

efefct of water on SiCl4 and PCl5

Answer 22

SiCl4 and PCl5 are dissolved in water

producing white fumes of HCl gas

Question 23

chemical bonding + structure of pd 3 chlorides

Answer 23

NA and MG ionic ie giant ionic

AL, SI, P, S covalent ie simple mol

Question 24

ph of pd 3 chlorides

Answer 24

na-7, mg-6.5, al-3, si p s- 2

Question 25

Electronegativity across period

Answer 25

Increases as electrons are more strongly attracted to their increasing nuclear charge hence strength of the atoms attraction for electrons in a bond increases

Question 26

Higher the en diff between oxygen and element more likely ..

Answer 26

Oxide will have ionic bonding electrons will be transferred from metal to oxygen to form ions