Ionic and Covalent Bonding

Question 1

What is ionic bonding?

Answer 1

the transferring of electrons between 2 oppositely charged particles

non metals gain an electron to become negatively charged,

vice versa they become electrostatically attracted gain noble gas arrangement

Question 2

What are the properties of ionic bonding?

Answer 2

• high melting point,
  
  • because a lot of energy is required to break the up the giant lattice of ions
• conduct electricity
  
  • when molten or dissolved in water (aqueous),
  • this is because ions that carry charge are free to move in the liquid state
• brittle and easily shatter,
  
  • because they form a lattice of alternating positive and negative ions,
  • a blow could cause the ions to move and produce contact between ions with like charges

Question 3

When does covalent bonding occur and what is covalent bonding?

Answer 3

• sharing outer electrons between non metals
• so that each atom has a stable noble gas arrangement a shared pair of electrons

Question 4

What holds covalent bonds together?

Answer 4

the electrostatic force between the nuclei of the element and the shared electrons

Question 5

What are the properties of substances with molecular structures?

Answer 5

• low melting point
  
  • because the strong covalent bonds are only between the atoms within the molecules.
  • There is only a weak attraction between the molecules so they don’t need much energy to move apart
• poor conductors of electricity
  
  • because the molecules are neutral overall,
  • there are no charged particles to carry the current,
  • even when dissolved in wate

Question 6

What is co-ordinate bonding?

Answer 6

where one atom provides both of the electrons also called dative covalent bonding

Question 7

What happens in a co-ordinate bond?

Answer 7

• the atom that accepts the electron pair is an atom that does not have a filled outer main level of electrons -
• the atom is electron-deficient
• the atom that is donating the electron has a pair of electrons that is not being used in a bond,
  
  • called a lone-pair

Question 8

Describe the bonding in the ammonium ion

Answer 8

• NH3, has a lone pair of electrons
• in the NH4+ ion, the nitrogen uses its lone pair of electrons to form a coordinate bond with an H+ ion
  
  • (a bare proton with no electrons at all
  • and therefore electron deficent covalently bonded atoms but is charged

Question 9

How are co-ordinate covalent bonds represented?

Answer 9

with an arrow, pointing towards the atom that is accepting the electron pair although

every bond has the same strength and length e.g H I + [H - N -> H+] I H

Question 10

Suggest why the melting point of sodium iodide is lower than the melting point of sodium bromide

Answer 10

iodide is a bigger ion, less attraction to the sodium atom.

Question 11

What is the bonding in iodine crystal? Why type of crystal describes the iodine crystal?

Answer 11

covalent between atoms, vdW between molecules

molecular crystal

Question 12

Why is heat required to melt the iodine crystal?

Answer 12

bonds between molecules must be brokemn

Question 13

Which period forms molecules with the highest melting points?

Answer 13

4

covalent bonds - forms a macromolecule

strong / many bonds need to be broken

lots of energy required

Question 14

In terms of the electrons involved, explain how the bond between the BF3 molecule and the F– ion is formed. Name the type of bond formed in this reaction.

Answer 14

• Lone pair donated / both electrons supplied by one atom 1 from F– (to B)
• dative/dative covalent/coordinate bonding

Question 15

Explain why calcium has a higher melting point than strontium.

Answer 15

• (For Ca) delocalised electrons closer to nucleus
• cationor it has fewer (electron) levels
• has stronger attraction between the cations and the delocalised electrons
• stronger metallic bonding