2.2 - Electons, Bonding And Structure

Question 1

Atomic orbital

Answer 1

A region around the nucleus that can hold up to 2 electrons with opposite spins

Question 2

Subshell

Answer 2

The collection of orbitals of the same type (at the same energy level)

Eg 2p, 3d, 4s,

Question 3

(Quantum) Shell

Answer 3

• energy levels

- a group of sub shells with the same principle quantum number (energy level)

Question 4

Principle quantum number (n)

Answer 4

• The number representing the overall energy of each orbital
• increases with distance from nucleus
• eg n=2 refers to the second shell

Question 5

How many electrons can be held in the:
A) first shell
B) second shell
C) third shell
D) fourth shell

Answer 5

A = 2
B = 8
C = 18
D = 32

Question 6

Describe an s-orbital

Answer 6

• spherical shape
• from n=1 each shell contains 1 s-orbital
• each s sub-shell can hold 2 electrons
• the greater the atomic number n, the larger the radius of the s-orbital

Question 7

Describe a p-orbital

Answer 7

• dumbbell shape
• from n=2 onwards there are 3 p-orbitals in each shell
• the 3 p orbitals are at right angles to each other and lie along the 3 Cartesian axes. They are referred to as the Px, Py and Pz orbitals
• each p sub-shell can hold 6 electrons
• the greater the shell number n, the further the p orbital is from the nucleus

Question 8

Describe a d-orbital

Answer 8

• from n=3 onwards, there are 5 d-orbitals

- each d orbital can hold 10 electrons

Question 9

Describe an f-orbital

Answer 9

• from n=4 onwards, there are 7 f-orbitals

- each f sub-shell can hold 14 electrons

Question 10

How do orbitals fill?

Answer 10

In order of increasing energy
-1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p,

Electrons pair with opposite spins
- electrons are negatively charged and repel eachother. Opposite spin counteracts repulsion

Orbitals with same energy are occupied singularly first
- one electron occupied each orbital singularly first to avoid repulsion before pairing starts

Question 11

Exceptional electron configurations

Answer 11

Cr = [Ar] 4s1 3d5

Cu= [Ar]4s1 3d10

This is because it is more stable in this configuration. For Cr, each 3D orbital is now half filled. For Cu, 3d sub-shell is now full

Question 12

What is the electron configurations ions?

Answer 12

Anions - gain electrons. Highest energy level will gain electrons first.

Cations - lose electrons. Highest energy level will lose electrons first.

Note: when 4s sub-shell is empty, it has a lower energy level than 3d so it is filled first. However, when it is filled, it has a higher energy level than 3d, so it is emptied first.

Question 13

Where are the s, p and d blocks on the periodic table?

Answer 13

S-block = has highest energy electrons in s-sub-shell. Left block of 2 groups on periodic table

P-block = has highest energy electrons in p-sub-shell. Right block of 6 groups on periodic table

D-block = has highest energy electrons in d-sub-shell. Centre block of 10 groups on periodic table

Question 14

What is ionic bonding?

Answer 14

Electrostatic force of attraction between positive actions and negative anions. It holds them in ionic compounds.

Question 15

Structure of ionic compounds

Answer 15

• each ion attracts oppositely charged ions in all directions
• this results in a giant ionic lattice structure containing billions of ions

Question 16

MP and BP of ionic compounds

Answer 16

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Question 17

Melting and boiling points of ionic compounds

Answer 17

• strong ionic bonds require lots of energy to overcome, resulting in high MP + BP
• mostly solid at room temp as there is insufficient energy to overcome strong electrostatic forces of interaction between oppositely charged ions
• MP higher for lattices with greater ionic charges as there is stronger attraction
• also depends on size of ions

Question 18

Solubility of ionic compounds

Answer 18

• many ionic compounds dissolve in polar solvents eg water as they break down lattice and surround each ion in solution
• in compounds with ions with large charges, these charges may be too strong for water to break, making them less soluble
• solubility requires 2 main processes:
  - ionic lattice must be broken down
  - water molecules must attract and surround the ions

Question 19

Electrical conductivity of ions

Answer 19

In solid state:

• ions are in a fixed position in giant ionic lattice
• there are no mobile charge carriers
• ionic compound is a non-conductor

In liquid or aqueous state:

• solid ionic lattice breaks down
• ions are now free to move as mobile charge carriers
• ionic compound is a conductor