2.4 - Electrons, bonding and structure

Question 1

Define the term ‘orbital’ ?

Answer 1

Orbital - A region of space about the nucleus holding up to 2 electrons with opposite spins

Question 2

What are the different types of orbitals ?

Answer 2

s, p, d, f

Question 3

What is the shape of s orbitals ?

Answer 3

Spherical

Question 4

What is the shape of p orbitals ?

Answer 4

Dumbbell-shaped

Question 5

What is the number of orbitals in the s, p, d and f sub-shells ?

Answer 5

• s = one orbital ( two electrons )
• p = three orbitals ( six electrons )
• d = five orbitals ( ten electrons )
• f = seven orbitals ( fourteen electrons )

Question 6

Do you know how to write electron configuration of atoms and ions ?

Answer 6

Yes

Question 7

What are the rules for how shells are occupied by electrons ?

Answer 7

• The orbitals fills from the lowest energy levels
• The 4s orbital fills up before the 3d orbital
• The 4s orbital loses electrons first before the 3d orbital

Question 8

Do you know how to write electron configuration using boxes ?

Answer 8

• Electrons will prefer to occupy orbitals on their own unless that option is unavailable
• Yes…

Question 9

What are the exceptions to the rules of electron configuration ?

Answer 9

• Chromium and Copper
• The 4s orbital is occupied by one electron and is not completed as the 3d orbital is filled

Question 10

Write the electron configuration for chromium and copper ?

Answer 10

• Chromium = 1s² 2s² 2p⁶ 3s² 3p⁴ 4s¹3d⁵
• Copper = 1s² 2s² 2p⁶ 3s² 3p⁴ 4s¹ 3d¹⁰

Question 11

Define the term ‘ionic bond’ ?

Answer 11

Ionic bond - The strong electrostatic attraction between oppositely charged ions

Question 12

What is the structure of ionic compounds ?

Answer 12

• They have a Giant Ionic lattice structure
• Each ion is surrounded by oppositely charged ions held together by strong ionic bonds
• The regular cubic arrangement gives the crystal its cubic shape

Question 13

Explain the structure of an ionic compound such as sodium chloride ( NaCl ) ?

Answer 13

• Each positive sodium ion is surrounded by six negative chlorine ions forming a giant ionic lattice
• The regular cubic arrangement gives the crystal its cubic shape

Question 14

Draw a diagram representing the structure of an ionic compound ( eg. NaCl ) ?

Answer 14

Question 15

What are the physical properties of ionic compounds ?

Answer 15

• High melting/ boiling point
• Only conducts electricity when molten/ solution
• Brittle
• Soluble in polar solvents ( eg. Water )

Question 16

Explain why ionic compounds have a high melting/ boiling point ?

Answer 16

Strong ionic bonds/ electrostatic attraction between oppositely charged ions require a lot of energy to break resulting in a high melting/ boiling point

Question 17

Explain why ionic compounds can only conduct electricity when molten/ solution ?

Answer 17

Ions are mobile when an ionic compound is molten/ solution and therefore carry a charge. Ions are not able to move when solid.

Question 18

Explain why ionic compounds are brittle ?

Answer 18

Applying a force causes like charged ions to align and therefore to repel

Question 19

Explain why ionic compounds are soluble in polar solvents ?

Answer 19

Polar solvents such as water can often dissolve ionic compounds

Question 20

Do you know how to draw dot and cross diagrams for ionic compounds ?

Answer 20

Yes

Question 21

Define the term ‘covalent bond’ ?

Answer 21

Covalent bond - The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Question 22

Define the term ‘dative covalent bond’ ?

Answer 22

Dative covalent bond - A covalent bond where both of the electrons come from the same species/ atoms

Question 23

Do you know how to draw dot and cross diagrams for covalent bonding ?

Answer 23

Yes

Question 24

What are double or triple covalent bonds ?

Answer 24

• A double covalent bond is two shared pair of electrons
• A triple covalent bond is three shared pair of electrons

Question 25

Do you know how to draw dot and cross diagrams to represent multiple and dative covalent bonding ?

Answer 25

Yes

Question 26

What is another name for a ‘dative covalent bond’ ?

Answer 26

A co-ordinated bond

Question 27

How are ions formed ?

Answer 27

- Metal atoms lose electrons to form positive ions ( cations ) - Non-metal atoms gains electrons to form negative ions ( anions )

Question 28

What does average bond enthalpy mean in regards to covalent bond strength ?

Answer 28

The higher the average bond enthalpy, the greater the strength of the covalent bonds

Question 29

Define the term 'electronegativity' ?

Answer 29

Electronegativity - the ability of an atom to attract the electrons in a covalent bond

Question 30

What are the factors affecting electronegativity ?

Answer 30

- Nuclear Charge - Atomic Radius - Shielding

Question 31

Explain how nuclear charge affects electronegativity ?

Answer 31

- As the number of protons increases in the nucleus, the greater the nuclear charge - This leads to stronger attraction between the nucleus and bonding pairs of electrons leading to an increase in electronegativity

Question 32

Explain how atomic radius affects electronegativity ?

Answer 32

- As the atomic radius decreases, the distance between the nucleus and bonding pairs of electrons decreases - This leads to stronger attraction between the nucleus and bonding pairs of electrons leading to an increase in electronegativity

Question 33

Explain how shielding affects electronegativity ?

Answer 33

- As the number of electrons increases, the number of inner electrons shells and therefore shielding increases - This leads to weaker attraction between the nucleus and bonding pairs of electrons causing the electronegativity to decrease

Question 34

What is the trend in electronegativity down the group ?

Answer 34

As you go down the group, the electronegativity decreases

Question 35

What is the trend in electronegativity across the period ?

Answer 35

As you go across the group, the electronegativity increases

Question 36

Explain why electronegativity decreases down the group ?

Answer 36

- The atomic radius increases due to an increased number of electrons shells - The shielding increases due to an increased number of electrons

Question 37

Explain why electronegativity increases across the period ?

Answer 37

- The nuclear charge increases due to more protons - Atomic radius decreases due to more protons in the nucleus - The shielding stays the same as all elements are in the same period

Question 38

Explain how atomic radius decreases across a period ?

Answer 38

- As you go across a period, the number of protons in the nucleus increases causing nuclear charge to increase - This means there is a greater attraction force between the nucleus and electrons - This means electrons within shells are held closer to the nucleus which decreases the atomic radius