TOPIC 1: Electron, Bonding and Structure Flashcards
Explain the different boiling points of NH3, F2 and BR2. (5)
- NH3 has hydrogen bonding b/w molecules
- F2 & Br2 have induced d.p-d.p forces
- intermolecular forces in Br2 stronger than in F2
^ bcs Br2 has more electrons
- Hydrogen bonding is stronger than the induced d.p-d.p forces in F2
State and explain two anomalous properties of ice caused by hydrogen bonding. (4)
- ice is less dense than water
^ ice has an open lattice - ice has a relatively high melting point
^ hydrogen bonds are relatively strong
Describe and explain the electrical conductivity of sodium oxide and sodium in their solid and molten states. (5)
- sodium conducts in solid and molten state
^ sodium has delocalised electrons in both states - sodium oxide conducts in molten state but not solid
^ molten sodium oxide has mobile ions
^ solid sodium oxide has immobile ions
Why is Na3PO4 described as a salt of H3PO4. (1)
- the hydrogen ions are replaced by sodium ions
Suggest why PH3 has a lower boiling point than NH3. (1)
- the intermolecular forces in PH3 are weaker
Define: a dative covalent bond
- both electrons have been donated by one atom
Explain why the student might expect the H-N-H bond angle to be larger in H3NBF3 than in NH3. (3)
- NH3 has 3 bonding pairs & 1 lone pair
of electrons - H3NBF3 has 4 bonding pairs of
electrons - lone pair on Nitrogen now becomes a
bonding pair
Explain why there is a difference in the melting points of K, KBr and H2O. (6)
- In K, there’s electrostatic attraction
b/w cations & electrons - In KBr, there’s electrostatic attraction
b/w oppositely charged ions - KBr has ionic bonding
- In H2O, there’s hydrogen bonding b/w
molecules - strength of forces: (bonding)
ionic > metallic > hydrogen
Define: electronegativity
- the ability of an atom to attract electrons
- in a covalent bond
Molecules of BF3 contain polar bonds, but the molecules are non polar.
Explain why. (2)
- BF3 is symmetrical
- the dipoles cancel out
Explain why a CH2Cl2 molecule is polar. (1)
- the dipoles do not cancel out
SbCl3 molecules are polar.
Explain. (2)
- there’s a difference in
electronegativity - molecules are not symmetrical and
dipoles do not cancel out
Describe how Van der Waals’ forces arise. (3)
- uneven distribution of electrons
- creates a temporary dipole
- causing induced dipoles in
neighbouring molecules
Suggest why there are no other intermolecular forces in solid sulfur. (1)
- no polar bonds
Explain why a molecule of SF6 has an octahedral shape. (2)
- sulfur has six bonded pairs
- electron pairs repel
Explain why a solution of copper(II) nitrate conducts electricity. (1)
- ions are mobile
State and explain the trend in the boiling points of chlorine, bromine and iodine. (3)
- b.p. increases down the group
- stronger intermolecular forces
- more energy needed to break these
intermolecular forces
Why would astatine be expected to react similarly to other halogens. (1)
- same number of outermost electrons
Explain why a solution of Copper(II) nitrate conducts electricity. (1)
- ions are mobile
Explain how ionic bonding holds the particles together in an ionic compound. (1)
- strong electrostatic attraction between positively charged ions & negatively charged ions