Bonding and Structure

Question 1

Define ionic bonds

Answer 1

Ionic bonds are strong electrostatic forces of attraction between oppositely-charged ions

Question 2

If in lattice of positive ions and negative ions, each positive ion(Y) is surrounded by eight negative ions and each negative(Z) surrounded by 4 positive ions, what is formula of compound

Answer 2

YZ2

Question 3

Why does sodium chloride have high melting points

Answer 3

Sodium chloride has giant ionic structure, large amount of energy required to overcome strong electrostatic forces of attraction between oppositely-charged ions

Question 4

Why does magnesium oxide have much higher melting point than sodium chloride?

Answer 4

(State charges of all ions)
Due to the greater charges, more energy is required to overcome the stronger electrostatic forces of attraction between magnesium ions and oxide ions compared to those between sodium ions and chloride ions

Question 5

Why does hydrogen chloride not conduct electricity in solid state

Answer 5

Oppositely-charged ions are held in fixed positions by strong electrostatic forces of attraction between oppositely-charged ions. Ions are not free-moving and cannot conduct electricity

Question 6

Why does aqueous hydrogen chloride conduct electricity

Answer 6

Strong electrostatic forces of attraction between oppositely-charged ions have been overcome. Ions are free-moving and can conduct electricity

Question 7

State solubility of ionic compounds in water and organic solvent

Answer 7

Soluble in water and insoluble in organic solvent

Question 8

Define electronegativity

Answer 8

Electronegativity refers to ability of atom to attract a shared pair of electrons towards itself in covalent bond

Question 9

Which element is the most electronegative

Answer 9

Fluorine

Question 10

What happens when two atoms involved in covalent bond have same or similar electronegativity

Answer 10

A non-polar covalent bond results and two atoms have equal pull on shared pair of electrons

Question 11

What happens when two atoms involved in covalent bond have different electronegativity values

Answer 11

Pair of shared electrons not equally shared and polar covalent bond results. More electronegtative atom acquires partial negative charge and less electronegative atom acquires partial positive charge

Question 12

Why does methane have low melting point

Answer 12

Has simple molecular structure, small amount of energy is required to overcome weak intermolecular forces of attraction

Question 13

Why is methane a non-conductor of electricity

Answer 13

Methane has a simple molecular structure, there are no free-moving valence electrons available to conduct electricity

Question 14

State solubility of simple molecules in water and organic solvent

Answer 14

Insoluble in water and soluble in organic solvents

Question 15

Define allotrope

Answer 15

Different forms of same element, allotropes may have different properties such as hardness or electrical conductivity

Question 16

State structure of diamond

Answer 16

A giant molecular structure, each carbon atom is covalently bonded to four other carbon atoms in a tetrahedral arrangement

Question 17

Why does diamond have very high melting point

Answer 17

Has giant molecular structure, large amount of energy is required to break strong covalent bonds between carbon atoms.

Question 18

Why does diamond not conduct electricity

Answer 18

Has giant molecular structure, all four valence electrons of each carbon atom are used for covalent bonding, no free-moving valence electrons present to conduct electricity

Question 19

Why is diamond hard

Answer 19

All carbon atoms are held by strong covalent bonds throughout the structure

Question 20

Why does graphite have high melting point

Answer 20

Graphite has giant molecular layered structure, a large amount of energy is required to overcome the strong covalent bonds between the carbon atoms

Question 21

Why does graphite conduct electricity

Answer 21

Each carbon atom uses three out of four valence electrons in bonding, valence electrons not used in bonding are free-moving to conduct electricity

Question 22

Why is graphite soft and slippery

Answer 22

Has giant molecular layered structure, layers of carbon atoms in graphite are held by weak intermolecular forces of attraction and can slide over one another when force is applied

Question 23

Define metallic bond

Answer 23

Strong electrostatic forces of attraction between positive metal ions and ‘sea’ of delocalised free-moving valence electrons

Question 24

Why do metals have high melting point

Answer 24

Metal has giant metallic structure, large amount of energy needed to overcome strong electrostatic forces of attraction between positive metal ions and ‘sea’ of delocalised free-moving valence electrons

Question 25

Why can metals conduct electricity

Answer 25

Metals has giant metallic structure, has a ‘sea’ of free-moving valence electrons present to conduct electricity

Question 26

Why are metals ductile and malleable

Answer 26

Metals have giant metallic structure, they are arranged orderly in layers and when force is applied layers of metal ions can slide over one another