Bonding

Question 1

What is electronegativity?

Answer 1

• the power of an atom to attract the pair of electrons in a covalent bond

Question 2

What increases the strength of an ionic bond?

Answer 2

• a higher ionic charge
• a smaller ionic radius

Question 3

What is an ionic bond?

Answer 3

• strong electrostatic force of attraction between oppositely charged ions.

Question 3

How to increase electronegativity?

Answer 3

• Increased nuclear charge of the atom (more protons)
• smaller atomic radius of the atom
• fewer number of principle energy levels

Question 4

What makes a bond polar or non polar

Answer 4

non-polar - bonded atoms have same or similar electronegativity

polar - bonded atoms have different electronegativity

Question 5

What is covalent bonding?

Answer 5

• a shared pair of electrons between atoms

Question 5

What increase the strength of a metallic bond?

Answer 5

• a higher ionic charge
• more delocalised electrons
• smaller atomic radius

Question 6

What is metallic bonding?

Answer 6

• strong electrostatic force of attraction between the positive metal ions and the sea of delocalised electrons

Question 6

Properties of Ionic Compounds

Answer 6

• always solid at room temperature due to the giant ionic lattice structure .This is because of the strong electrostatic attraction between the oppositely charged ions
• not conductive as a solid (only when molten or dissolved in water) as the delocalised electrons aren’t free to carry the charge through the whole structure

Question 7

What is the VSEPR theory?

Answer 7

It predicts the shapes of molecules based on the idea that electrons repel each other.

LP-LP repulsion > BP-LP repulsion > BP-BP repulsion

Question 7

Properties of metals

Answer 7

• good conductors of electricity and heat as the delocalised electrons are free to move and flow
• high melting and boiling points due to the strong attraction between the ions and delocalised electrons
• malleable and ductile meaning they can be hammered into shape due to the layers of ions that can slide over each other

Question 8

What is coordinate bonding?

Answer 8

When the shared pair of electrons in the covalent bond come from only one of the bonding atoms

Question 9

What shape and angle is 3 bonding pairs?

Answer 9

Trigonal Planar and 120 degrees

Question 9

What shape and angle is 2 bonding pairs?

Answer 9

Linear and 180 degrees

Question 10

What shape and angle is 4 bonding pairs?

Answer 10

Tetrahedral and 109.5 degrees

Question 11

What shape and angle is 2 bonding pairs and 2 lone pairs?

Answer 11

V-shaped and 104.5 degrees

Question 12

What shape and angle is 3 bonding pairs and 1 lone pair?

Answer 12

Trigonal Pyramid (Pyramidal) and 107 degrees

Question 12

How much do lone pairs distort bond angles

Answer 12

• they reduce bond angles by 2.5°

Question 12

What shape and angle is 6 bonding pairs?

Answer 12

Octahedral and 90 degrees

Question 12

How to describe how you have deduced the shape of a molecule

Answer 12

• Compound has X lone pairs and Y bonding pairs
• Electron pairs repel ( lone pairs repel more)
• Bond angle is (reduced to)

Question 13

What shape and angle is 5 bonding pairs?

Answer 13

Trigonal Bipyramidal and 120 and 90 degrees

Question 13

What shape and angle is 4 bonding pairs and 2 lone pairs?

Answer 13

Square Planar and 90 degrees

Question 13

How would you work out whether a molecule is polar or non-polar?

Answer 13

Asymmetrical molecule = polar

Symmetrical molecule = non polar

Question 13

How do VdW forces arise?

Answer 13

• electrons randomly move around the molecule and one side becomes more negative than the other
• this is called a temporary dipole
• the temporary dipole induces a dipole in another molecule
• there is an attraction between the partially positive charge on one molecule and the partially negative charge on another

Question 14

What are the three intermolecular forces and what is their order in strength

Answer 14

- hydrogen bonding (strongest) - permanent dipole-dipole forces - Van der Waals forces (weakest)

Question 14

what factors affect the strength of VdW forces

Answer 14

- the size/Mr of the molecule (bigger = stronger VdW forces) - surface area contact (more SA contact = stronger VdW forces)

Question 14

how does hydrogen bonding arise?

Answer 14

- Oxygen, Nitrogen and Fluorine are very electronegative - there is a big difference in electronegativity between O/N/F and the hydrogen so they pull the pair of electrons in the bond strongly towards them - this makes the hydrogen partially positive and a lone pair on a neighbouring O/N/F is then attracted to the hydrogen

Question 14

how do permanent dipole-dipole forces arise?

Answer 14

- there is a polar bond due to a difference in electronegativity between atom X and atom Y resulting in a permanent dipole - there is an attraction between the partially positive charge on one molecule and the partially negative charge on another