L8 & 9: Covalent Bonding Flashcards
True or false: In covalent bonding, electron pairs are shared by both participating atoms
True
True or false: Covalent bonds are directional
True
True or false: Covalent bonds form between metals and non-metals
False. Covalent bonds form between the atoms of the same or different non-metal elements
True or false: Covalent bonding is found in organic compounds
True
True or false: When atoms interact to form molecules, the overall number of orbitals must remain the same
True
What is a Lewis Structure?
A graphic representation of the valence electrons of an atom. Each electron is represented by dots and crosses.
True or false: Covalent bonding is favoured by atoms with low ionisation energy
False. Covalent bonding is favoured by those with high ionisation energy
True or false: Covalent bonding is favoured by atoms of equal electron affinity and equal electronegativity
True
True or false: Covalent bonding is favoured by atoms with a high nuclear charge
True
True or false: Covalent bonding is favoured by atoms with a large atomic size
False. Covalent bonding is favoured by atoms with a small atomic size
True or false: Most MCQ options that say “always” or “never” are wrong
True
Fill in the gap:
Covalent compounds are __________ electrical conductors.
poor
Fill in the gap:
Covalent compounds tend to have ____(1)____ melting points and ____(2)_____ boiling points
(1) low
(2) low
If covalent bonds are strong, why do covalent compounds have low melting and boiling points?
Although the molecules are strong, the non-covalent intermolecular forces that hold the covalent molecules together are weak
True or false: Covalent compounds are insoluble
Sometimes soluble; sometimes insoluble - depends on the intermolecular bonding with solvent
How do you get a polar covalent bond?
Between atoms that have a significant difference in electronegativity, but not enough to form an ionic bond.
Covalent or ionic?
High melting point, high boiling point
Ionic
Covalent or ionic?
Conduct electricity when melted
Ionic
Covalent or ionic?
Many soluble in non-polar liquids but not in water
Covalent
Covalent or ionic?
Poor electrical conductors in any phase
Covalent
Covalent or ionic?
Solids, liquids or gases
Covalent
Covalent or ionic?
Crystalline solids
Ionic
Covalent or ionic?
Many soluble in water but not in non-polar solvents
True or false: When one atom donates both electrons to a covalent bond, it is known as a dative covalent bond
True. The atom that supplies the shared pair of electrons is known as the donor and the other atom is the acceptor - simples!
Which 3 polyatomic ions are found with dative covalent bonding?
1) Transition metal complex ions
2) Nitrogen-containing complexes (such as the ammonium ion)
3) Hydroxonium ion
True or false: Carbon monoxide and nitric acid display dative covalent bonding
True
What are the 2 key requirements for a dative covalent bond to form?
1) The donor must have a lone pair of e-
2) The acceptor must have a vacant orbital to house the donated pair
How is ammonium formed?
Ammonia forms a dative covalent bond with H+.
Ammonia is the donor and H+ is the acceptor
How are complex ions formed?
When transition metal ions and Al3+ are dissolved in water
Are the melting and boiling points of a co-ordinate compound higher or lower than that of a purely covalent compound?
Higher
Are the melting and boiling points of a co-ordinate compound higher or lower than that of an ionic compound?
Lower
Are co-ordinate compounds electrical conductors?
No
What physical states can co-ordinate compounds exist in?
Solid, liquid, or gas
What is the solubility of co-ordinate compounds?
Soluble in non-polar solvents; less soluble in polar solvents (can react with water)
Where do dative bonds occur in biology?
When biological molecules bind to metal ion-containing cofactors
The function of the drug dimercaprol depends on its ability to form dative covalent bonds. What is the function of dimercaprol?
Treats mercury and arsenic poisoning
The function of the drug desferoxamine depends on its ability to form dative covalent bonds. What is the function of desferoxamine?
Treats iron overdose
The function of the drug d-penicillinamine depends on its ability to form dative covalent bonds. What is the function of d-penicillinamine?
Treats copper and arsenic poisoning
The function of the drug cis-platin depends on its ability to form dative covalent bonds. What is the function of cis-platin?
Anticancer agent
True or false: Valence Shell Electron Pair Repulsion (VESPR) theory can predict the shape of a molecule
True
If a molecule has only bonding pairs of electrons, what are the 5 shapes the molecule could assume? What are the bond angles of each shape?
1) Linear (180)
2) Trigonal planar (120)
3) Tetrahedral (109.5)
4) Trigonal bipyramidal (90 and 120)
5) Octahedral (90)
How do you predict whether a molecule is polar?
1) Are the bonds polar? If not, the molecule will not be polar
2) What shape is the molecule? Do the dipole cancel each other out?
