Chapter 5 (2.2.1/2)

Question 1

Describe shells

Answer 1

• shells are regarded as energy levels
• energy increases as shell no. increases
• shell number or energy level number is called the principal quantum number, n

Question 2

What are atomic orbitals?

Answer 2

An atomic orbital is a region around the nucleus that can hold up-to 2 electrons, with opposite spins. Shells are made up of atomic orbitals.

Question 3

Describe s-orbitals

Answer 3

• electron cloud is within the shape of a sphere
• each shell from n=1 has 1 s-orbital
• the greater the shell number, n, the greater the radius of its s-orbital

Question 4

Describe p-orbitals

Answer 4

• electron shape within the shape of a dumb-bell
• 3 separate p-orbitals at right angles to one another: px, py, pz
• each shell from n=2 has 3 p-orbitals
• the greater the shell number, the further the p-orbital is from the nucleus

Question 5

Describe d-orbitals

Answer 5

• each shell from n=3 has 5 d-orbitals

Question 6

What happens to orbitals within each shell?

Answer 6

within each shell, orbitals of the same type are grouped together as sub-shells

Question 7

How do orbitals fill?

Answer 7

Within each shell, the new type of sub-shell added has a higher energy + orbitals fill in order of increasing energy.

Question 8

Describe how electrons pair with opposite spins

Answer 8

• electrons repel one another since they are negative
• they have a spin - either up or down
• electron is shown as an arrow indicating spin
• 2 electrons in an orbital must have opposite spins. This helps counteract the repulsion between the negative charges

Question 9

How are electrons occupied in orbitals?

Answer 9

-Within a sub-shell, 1 electron occupies each orbital before pairing starts, preventing any repulsion between paired electrons until there is no further orbital available at the same energy level

Question 10

How is Periodic table divided into blocks

Answer 10

Highest energy sub shell in…..
S-block - s sub shell (left 2 block groups)
P-block - p sub shell (right 6 block groups)
D-block - d sub shell (centre 10 groups)

Question 11

How are ions formed for s / p block elements?

Answer 11

Highest energy sub shell (eg.3s) will be lost first

Question 12

How are ions formed for d block elements?

Answer 12

• 4s fills first but also empties compared to 3d

- 4s at a lower energy level when filling, but higher when emptying

Question 13

Ionic bonding

Answer 13

Electrostatic attraction between positive + negative ions. Holds together cations + anions in ionic compounds.

Question 14

Structure of ionic compounds

Answer 14

• Each ion attracts oppositely charged ions in ALL directions.
• Results in a giant ionic lattice structure containing billions of ions (actual number only determined by crystal size)

Question 15

Effect of structure on melt/boil points (ionic)

Answer 15

• At RTP, Insufficient energy to overcome forces in the lattice so High temperatures needed.
• melting points are higher for ions w/ higher charges- stronger attraction between ions
• also depends on size of the ions (bigger= higher)

Question 16

How Ionic compounds dissolve?

Answer 16

• They dissolve in polar solvents (water)

- Polar solvent molecules form IM bonds with the solute surrounding the ions from the solute causing it to dissolve.

Question 17

Solubility requires…

Answer 17

• Ionic lattice must be broken down

- Polar solvent molecules must attract/ surround the ions

Question 18

When an ionic compounds have large charges….

Answer 18

The attraction may be too strong for water to be able to break down the lattice structure, so a stronger polar solvent may be needed.

Question 19

Solubility dependent on…

Answer 19

Relative strengths of attractions within the giant ionic lattice + attraction between ions and water (solvent) molecules

Question 20

Pattern for solubility

Answer 20

Solubility decreases as ionic charge increases

Question 21

Electrical conductivity of ionic compounds in the solid state

Answer 21

• ions are in fixed positions in the giant ionic lattice
• there are no mobile charge carriers
  Non conductors of electricity in the solid state

Question 22

Electrical conductivity of ionic compounds in the liquid state

Answer 22

• the solid ionic lattice breaks down
• the ions are now free to move as mobile charge carriers
  conductors of electricity in liquid and aqueous states

Question 23

What is a covalent bond?

Answer 23

The strong electrostatic forces of attraction between a shared pair of electrons + the nuclei of the bonded atoms

Question 24

Where do covalent bonds occur?

Answer 24

• a small molecule e.g. H2
• a giant covalent structure e.g. SiO2
• a charged polyatomic ion e.g. NH4+

Question 25

What is a covalent bond in terms of orbitals?

Answer 25

- a covalent bond is the overlap of atomic orbitals, each containing 1e-, to give a shared pair of electrons - shared pair = attracted to the nuclei of both the bonding atoms

Question 26

Describe a localised covalent bond

Answer 26

- in a covalent bond, the attraction is localised, acting solely between the shared pair of electrons+ the nuclei of 2 bonded atoms - the result is a molecule

Question 27

What are lone pairs?

Answer 27

Lone pairs are pairs of electrons that are not shared

Question 28

How can SF6 have 12 outer shell electrons?

Answer 28

- the 6 unpaired electrons from sulfur become paired - outer shell now has 12 electrons - more than the nearest noble gas - expansion of the octet - only possible from n=3 shell, when a d-sub-shell become available for the expansion

Question 29

When do multiple covalent bonds exist?

Answer 29

Multiple covalent bonds exists when 2 atoms share more than one pair of electrons

Question 30

What is a double/triple covalent bond?

Answer 30

In a double/triple covalent bond, the electrostatic forces of attraction are between 2/3 shared pairs of electrons + the nuclei of the bonding atoms

Question 31

What is a dative covalent bond?

Answer 31

- a covalent bond in which the shared pair of electrons has been supplied by one of the bonding pairs only - shared pair was originally a lone pair from one of the bonded atoms

Question 32

What is average bond enthalpy?

Answer 32

- serves as a measurement of covalent bond strength - kJ/mol - the larger the value of the average bond enthalpy, the stronger the covalent bond