Chemical Bonding(1)

Question 1

What is a metallic bond

Answer 1

• strong electrostatic attractions that exist between the metal ions and sea of delocalised electrons in a giant metallic structure

Question 2

Physical properties of Giant Metallic Lattice

Answer 2

• high melting points
• high electrical conductivity
  — prescence of delocalised valence electrons

Question 3

Factors affecting strength of metallic bond

Answer 3

• no. of valence electrons electrons available for metallic bonding
• ionic radius of metal cation

Question 4

What is Ionic bond

Answer 4

• strong electrostatic attractions that exist between the cation and anion in the ionic lattice

Question 5

What are physical properties of ionic bonding

Answer 5

• high melting point
• soluble in water and other polar solvents
• good electrical conductor when in molten state or aqueous
• non-electrical conductor in solid as ions can only vibrate about fixed positions

Question 6

Factors affecting strength of ionic bond

Answer 6

• charge and size of ionic radius
• larger the charge size and smaller the ions the stronger the electrostatic forces of attraction
• charge density is irrelevant

Question 7

What is a coordination number

Answer 7

• no. of nearest ions that surround another ion of the opposite charge in an ionic lattice
• relative size of ions and charge

Question 8

What is a covalent bond

Answer 8

• strong electrostatic attraction between a shared pair of electrons and two positively charged nuclei

Question 9

What is a sigma bond

Answer 9

• valence orbitals overlap along inter-nuclear axis, a single region of head-on overlap is produced

Question 10

What is a pi bond

Answer 10

• side-on overlap of p orbitals will result in two regions of overlap

Question 11

What is a co-ordinate bond(dative bond)

Answer 11

• shared electron pair comes from one atom
• donor has lone pair of electrons, acceptor has vacant low lying orbitals

Question 12

What is electronegativity

Answer 12

• measure of its ability to attract the shared pair of electrons in a covalent bond to itself
• increases across period
• decrease down the group

Question 13

What is bond polarity

Answer 13

• difference in electronegativity
• bonding electrons are drawn towards more electronegative atom
• more electronegative atoms will acquire partial negative while the other a partial positive charge
• permanent separation of charges is a dipole

Question 14

Strength of covalent bond

Answer 14

• bond energy and bond length are indicators of strength of covalent bond

Question 15

Bond energy

Answer 15

• amount of energy required to break one mole of covalent bond between 2 atoms in gaseous state
• stronger the covalent bond —> higher bond energy

Question 16

Bond length

Answer 16

• distance between nuclei of two atoms in the bond
• shorter bond length indicates stronger covalent bond

Question 17

Factors affecting covalent bond strength

Answer 17

• effectiveness of orbital overlap
• difference in electronegativity between bonding atoms
• number of bonding electrons

Question 18

How does effectiveness of orbital overlap affect covalent bond strength(from Cl to I)

Answer 18

• As atoms from Cl to I becomes larger, size of valence orbitals increases
• these larger orbitals become more diffused and when they overlap, the accumulation of electron density with inter-nuclei region is lower
• orbital overlap is less effective resulting in weaker bond strength

Question 19

How does difference in electronegativity between bonding atoms affect covalent bond strength

Answer 19

• since electronegativity increases in the order N<O<F, bond polarity increases in the order N-H<O-H<F-N
• in addition to existing covalent bond there is increase in the electrostatic attraction between the two partial charges
• therefore an increase in bond strength

Question 20

How does number of bonding electrons affect strength of covalent bond strength

Answer 20

• as number of bonding electrons increases within the inter-nuclei region for multiple bonds,
• the attractive forces for these electrons increases
• covalent bond strength increases