Periodic Table(I)

Question 1

Atomic radius and its trend across the period

Answer 1

• is defined as half the distance between the nuclei of two adjacent atoms of the same element
• across the period
• nuclear charge increases
• no. of electrons increases but they are added to the same outermost electron shell and hence number of electron shells remain the same and shielding effect remains approximately constant
• stronger electrostatic forces of attraction between nucleus and valence electrons
• atomic radius decreases across period

Question 2

Atomic radius(trend down the group)

Answer 2

• down the group
• nuclear charge increases
• number of filled principal quantum shells increases
• valence electrons are further from the nucleus and more shielded
• weaker electrostatic forces of attraction between the nucleus and the valence electrons
• atomic radius increase down the group

Question 3

Ionic radius and its trend from Na⁺ to Si⁴⁺, P^3- to Cl^-

Answer 3

• defined as half the distance between the nuclei of two adjacent ions of the same element
• nuclear charge increases
• number of filled principal quantum shells and shielding effect remains the same since cations and anions are isoelectronic
• there are stronger electrostatic forces of attraction between the nucleus and the valence electrons
• ionic radius decreases

Question 4

Ionic radius(trend from Si⁴⁺ to P^3-)

Answer 4

• nuclear charge increases
• P^3- has one more filled principal quantum shell compared to Si⁴⁺
• the valence electrons in P^3- are further from the nucleus than in Si⁴⁺ and more shielded
• weaker electrostatic forces of attraction between nucleus and valence electron in P^3- than in Si⁴⁺
• hence ionic radius of P^3- is greater than Si⁴⁺

Question 5

Comparison between cationic radius and an atomic radius

Answer 5

• cationic radius is smaller than atomic radius
• nuclear charge remains the same
• cation has one principal quantum shell lesser than the atom
• valence electrons in the cation are closer to the nucleus and less shielded from the nucleus
• stronger electrostatic forces of attraction between nucleus and valence electrons in cation

Question 6

Comparison between anionic radius and atomic radius

Answer 6

• anionic radius is larger than atomic radius
• nuclear charge remains the same
• anion has more electrons than atom
• inter-electronic repulsion increases, resulting in the valence electrons further away from nucleus
• weaker electrostatic forces of attraction between the nucleus and the valence electrons in anion

Question 7

Electronegativity and its trend across the period

Answer 7

• refers to the ability of an atom to attract the shared pair of electrons in a covalent bond
• across the period
• nuclear charge increases
• no. of electrons increases but these electrons are added to the same outermost electron shell and hence number of electron shells remaining the same and shielding effect remains approximately constant
• there are stronger electrostatic forces of attraction between nucleus and the electron pair in a covalent bond
• electronegativity increases

Question 8

Electronegativity(trend down the group)

Answer 8

• nuclear charge increases
• number of filled principal quantum shell increases
• valence electrons are further from the nucleus and more shielded
• weaker electrostatic forces of attraction between the nucleus and the electron pair in a covalent bond
• electronegativity decreases

Question 9

The Diagonal relationship in periodic table

Answer 9

• the head element of each group may resemble elements positioned diagonally to it, both physically and chemically
• can have similar electronegativity giving rise to similar properties
• Li₂CO₃ undergoes similar thermal decomposition as MgCO₃
• Be(OH)₂ exhibits amphoteric character and can react with acids and alkalis similar to Al(OH)₃
• Both B and Si are used as semiconductors

Question 10

Boiling point of Si*(1414 degrees Celcius)

Answer 10

• Si has a giant molecular structure
• very large amount of energy is required to overcome the extensive network of strong covalent bonds between atoms in the three dimensional network structure

Question 11

Hydration in metallic chlorides

Answer 11

• physical process
• water molecules surround the cations, forming ion-dipole interactions with Na⁺
• forms dative bonds in [Mg(H₂O)₆]²⁺ and [Al(H₂O)₆]³⁺

Question 12

What is hydrolysis

Answer 12

• breaking of a covalent bond in a molecule using water
• changes pH of solution