Module 2: Chapter 5 (Electrons and Bonding)

Question 1

How many electrons can fit in the first four main shells?

Answer 1

1 = 2
2 = 8
3 = 18
4 = 32

Question 2

Name the sub-shells in the first four shells

Answer 2

1 = 1s -> 2e-

2 = 2s -> 2e-
2p -> 6e-

3 = 3s -> 2e-
3p -> 6e-
3d -> 10e-

4 = 4s -> 2e-
4p -> 6e-
4d -> 10e-
4f -> 14 e-

Question 3

What is a ‘main shell’ also referred to as?

Answer 3

principal quantum number, n

Question 4

What is the electronic configuration order of subshells?

Answer 4

In order of increasing energy…

1s2s2p3s3p4s3d4p

Question 5

How is a shorthand version of configuration made?

Answer 5

Giving the previous noble gas in the periodic table, plus the remaining outer shell electrons

Question 6

How is electron configuration constructed for ions?

Answer 6

‘last in-first out’

exception of 4s, so 4s empties before 3d, as it has a slightly lower energy level

Question 7

What are the different blocks of the periodic table?

Answer 7

• Hydrogen and Groups 1+2 are s-block
• Transition metals are d-block
• Groups 3-8(0) are p-block
• Extra are f-block

Question 8

What is an atomic orbital?

Answer 8

An orbital describes the region of space where there is a high probability of finding an electron

Question 9

How many electrons are in each orbital?

Answer 9

each orbital can only hold 2 electrons

Question 10

How do electrons behave in orbitals?

Answer 10

Electrons in the same orbital have to have opposite spins

- as far as possible electrons in the same sub-shell prefer to be in separate orbitals to minimize repulsion

Question 11

Describe a s-orbital

Answer 11

• electron cloud is within the shape of a sphere

- the greater the shell number n, the greater the number of its s-orbital

Question 12

Describe a p-orbital

Answer 12

• electron cloud is within the shape of a dumb-bell
• the three separate p-orbitals are at right angles to each other
• the greater the shell number n, the further the p-orbital from the nucleus

Question 13

What is an ionic bond?

Answer 13

the electrostatic attraction between positively and negatively charged ions

Question 14

What do dot and cross diagrams show?

Answer 14

used to distinguish where the electrons originally came from

Question 15

Describe the structure of ionic compounds

Answer 15

• in the compound every ion attracts oppositely charged ions in all directions
• the result is a giant ionic lattice

Question 16

What are the properties of ionic compounds?

Answer 16

• in general the physical properties of a substance are always explained by consideration of structure and bonding
• generally most compounds have a high mp/bp (solid at room temp)
• due to the very strong electrostatic attraction between oppositely charged ions, lots of energy is needed to break the lattice

Question 17

Describe the electrical conductivity of ionic compounds

Answer 17

• solid ionic compound will no conduct electricity as the ions can’t move and carry charge, in fixed positions in the lattice
• only carry charge unless molten or dissolved

Question 18

Describe solubility of ionic compounds

Answer 18

• often not always soluble in water, tend to be insoluble in most other solvents
• water is polar
• in a solution an ion can attract many water molecules
• the compound will tend to be soluble if the attractions formed compensate for those broken down when the lattice breaks down
• it is a fine balance, making predictions about solubility difficult

Question 19

What is a covalent bond?

Answer 19

covalent bonding is electrostatic attraction between shared pair of electrons and the nuclei of the two bonded atoms

Question 20

Describe a covalent bond

Answer 20

• a covalent bond is formed by the overlap of atomic orbitals
• in a covalent bond the attraction is localised, this is in contrast to ions which can attract in all directions

Question 21

How many bonds does carbon, hydrogen, nitrogen and oxygen form?

Answer 21

4, 1, 3, 2

Question 22

How many orbitals does each subshell have?

Answer 22

• an s subshell has 1 orbital
• p has 3 orbitals
• d has 5 orbitals
• f has 7 orbitals

Question 23

What is a dative covalent bond?

Answer 23

A dative covalent bond is a shared pair of
electrons where both electrons are from the
same atom.