Bonding Flashcards
What is an ionic bond?
The strong electrostatic attraction between oppositely charged ions which forms a giant ionic lattice
Name 3 properties of an ionic bond.
- High melting and boiling point
- Electrical conductivity
- Brittle and break easily
What is a metallic bond?
The strong electrostatic attraction between positive ions and delocalised electrons
Why does Mg have a higher boiling point than Na?
3 marks
- Both have giant metallic lattic structure/ electrostatic attractions between + ions and delocalised electrons
- Mg has a greater nuclear charge (2+) and more delocalised electrons
- Mg is smaller so has greater charge density
- Therefore stronger metallic bonds in Mg which requires more energy to break
Name 5 properties of a metallic bond.
- Electrical conductivity
- Thermal conductivity
- Strong
- Malleable+ ductile
- High melting and boiling points
What is a covalent bond?
Shared pair of electrons between 2 atoms due to attraction between electrons and nucleus being stronger than repulsion
Name 2 properties of a covalent bond.
- Low melting and boiling points
- Poor conductors
Name the three macromolecular structures.
- Carbon allotropes
- Silicon
- Silicon oxide
What is a coordinate bond?
A shared pair of electrons that come from the same atom
Decribe the bond between N in NH3 and a H+ ion.
N donates its lone pair of electrons to H+
State the shapes and bond angles of molecules with 0 lone pairs and 2, 3, 4, 5, 6 bonding pairs.
- Linear: 180
- Trigonal planar: 120
- Tetrahedral: 109.5
- Trigonal bipyramidal: 90 and 120
- Octahedral: 90
State the shapes and bond angles of molecules with 1 lone pair and 2, 3, 4, 5 bonding pairs.
- V-shape: 117.5
- Pyramidal: 107
- Seesaw: 119 and 89
- Square pyramidal: 89
State the shapes and bond angles of molecules with 2 lone pairs and 2, 3, 4 bonding pairs.
- V-shape: 104.5
- Trigonal planar: 120
- Square planar: 90
What is electronegativity?
The power of an atom to attract a pair of electrons in a covalent bond
Must say IN A COVALENT BOND
What is the most electronegative element?
Fluorine
How is a polar bond formed?
- One atom is more electronegative than another
- Causes uneven distribution of electron density (dipole)
What is a hydrogen bond?
- Strongest intermolecular attraction
- Occurs between lone pair on F, N, O and H on another molecule
How do hydrogen bonds arise?
- Large difference in electronegativity between atom and H
- Creates a strong dipole on bond
- Lone pair on atom attracts H d+ on another molecule
What types of molecules do permanent dipole-dipoles from?
Polar molecules
How do permanent dipole-dipoles arise?
- Difference in electronegativity between atoms on two different molecules
- Forms dipole that doesn’t cancel out
- d- molecule attracts d+ molecule
What are induced dipole-dipoles?
- Weakest intermolecular force
- Occurs in non-polar molecules
How do induced dipole-dipoles arise?
- Random movement of electrons
- Causes uneven distribution of electron density which is a temporary dipole
- This induces a dipole in another molecule
- d+ molecule attracts d- molecule
Predict the shape of AlH4- ion and explain it.
(3 marks)
- Tetrahedral
- Equal repulsion
- Between 4 bonding pairs
Why does NaCl have a high melting point?
(3 marks)
- Ionic bonds
- Strong electrostatic forces of attraction that require lots of enery to break
- Between Na and Cl/ oppositely charged ions
Why does PH4+ not form hydrogen bonds?
(1 mark)
Difference in electronegativity is too small
Why is the bonding in nitrogen oxide covalent and not ionic?
(1 mark)
Small difference in electronegativity
In terms of IMFs why PH3 is almost insoluble in water?
(1 mark)
Does not form hydrogen bonds with water
In terms of electronegativity, why is the boiling point of H2S2 lower than H2O2?
(2 marks)
- Electronegativity of S is lower than O
- Only VDWs between H2S2 molecules (no hydrogen bonds)
Why is SbCl3 polar?
(3 marks)
- Difference in electronegativity between Sb and Cl (dipole)
- Molecule is not symmetrical
- Dipoles do not cancel out
Explain why the melting point of XeF4 is higher than the melting point of PF3. Give the shape of each molecule, why it has that shape and how the shape influences the forces.
Stage 1: e pairs
- XeF4 has 4bp and 2lp around Xe
- PF3 has 3bp and 1lp around P
Stage 2: shapes
- XeF4 is square planar
- PF3 is pyramidal- Electron pairs all repel but Lone pairs repel more than Bonding pairs
Stage 3: IMF
- XeF4 has IDDs only (symmetrical) and PF3 has PDDs
- More IMFs in XeF4
- Due to larger Mr/ more electrons/ larger molecules
Make sure to explain and compair strengths of IMFs
XeF4 is symmetrical therefore IDDs only (since dipoles cancel out)
What is the bonding in ammonium chloride?
(1 mark)
Covalent, Dative and Ionic
State the bond angle and shape in H2O and explain them
(4 marks)
- V-shape
- 104.5 degrees
- Lone pairs repel more strongly than bonding pairs
- So bond angle decreases from 109.5 degrees
Explain how IDDs arise in an SiF4 molecule and why no other type of intermolecular force exists
(3 marks)
- Uneven distribution of electron (density) in one molecule induces dipole in another molecule
- Symmetrical and dipoles cancel
- No hydrogens bonded to F so no hydrogen bonding
Explain why sodium bromide has a higher melting point than sodium and sodium iodide
(6 marks)
Stage 1: Na
- Na has metallic bonding
- Attraction between positive metal ions and delocalised electrons
- Forms giant/ lattice structure
Stage 2: NaBr and NaI
- Ionic bonding in NaBr and NaI
- Electrostatic attraction between oppositely charged ions
- Forms giant/ lattice structure
Stage 3: Comparison
- Ionic bonds are stronger than metallic bonds
- There is a stronger attraction between opposite ions in NaBr than NaI
- Since Br ion is smaller than I ion
Make sure you write about Br and I ions
Make sure you write about metallic/ ionic lattices
