EL 3&4: Electronic configuration, atomic structure

Question 1

What term describes the number of an electron shell, e.g. n = 2?

Answer 1

Principal quantum number.

Discrete numbers describing most probable distance of electrons from nucleus

Question 2

What are the shapes of:

• s-orbitals?
• p-orbitals?

Answer 2

• s-orbitals: spherical
• p-orbitals: 3 “8” shapes on x, y + z axes

Question 3

When there is more than one orbital with the same energy, these are first filled singly by electrons. Why is this?

Answer 3

• Keeps electrons as far apart as possible, minimising repulsion
• Uses smallest amount of energy possible

Question 4

• Electrons occupying the same orbital have __ spins
• Electrons singly occupying neighbouring orbitals have __ spins

Answer 4

• Opposite
• Parallel

Question 5

What 4 pieces of information are needed to describe an electron’s position?

Answer 5

• Shell (n)
• Sub-shell (s/p/d/f)
• Orbital
• Spin

Question 6

• What is the maximum number of electrons that can be held in each type of sub-shell?
• How many orbitals does each contain?

Answer 6

• s: 2 (1 orbital)
• p: 6 (3 orbitals)
• d: 10 (5 orbitals)
• f: 14 (7 orbitals)

Question 7

What are the maximum number of electrons which can be held in the first 4 shells?

Answer 7

• 2 (1s)
• 8 (2s, 2p)
• 18 (3s, 3p, 3d)
• 32 (4s, 4p, 4d, 4f)

Question 8

Draw a diagram showing the energies of the electron sub-shells from n = 1 to n = 4.

Answer 8

Question 9

When is it correct that energy of 3d > energy of 4s?

Answer 9

Period 3 elements and up to nickel in period 4.

Question 10

How does the modern periodic table group elements?

Answer 10

Groups elements in order of increasing atomic number, + according to their common properties.

Mendeleev used increasing mass number

Question 11

Indicate the following on the periodic table:

• s-block
• p-block
• d-block
• f-block

Answer 11

• s-block: groups 1-2
• p-block: groups 3-0
• d-block: transition metals
• f-block: lanthanides + actinides

Question 12

How can you deduce an element’s electron configuration from the periodic table?

Answer 12

• Period: outer shell number
• Group: number of e^- in outer subshell

Question 13

Draw an energy level diagram showing the arrangement of electrons in atomic orbitals in a ground state sodium atom.

Answer 13

1s²2s²2p⁶3s¹

Question 14

What is the electronic configuration of vanadium?

Answer 14

Z = 23

4s fills before 3d

1s²2s²2p⁶3s²3p⁶3d³4s²

Question 15

Name the following elements:

• [Ne]3s²3p⁵
• [Ar]4s¹
• [Ar]3d²4s²
• [Kr]4d¹⁰5s²5p²

Answer 15

• Chlorine
• Potassium
• Titanium
• Tin

Question 16

What is the term given to the occurence of periodic patterns?

Answer 16

Periodicity

Question 17

Answer 17

A, C, E (2)

Question 18

What is the term given to atoms or ions with full sub-shells?

Answer 18

Closed shell arrangement.

Question 19

Why exactly do group 2 elements share similar properties?

Answer 19

All have 2 electrons in outermost s-subshell

Question 20

Describe the periodicity of melting points in periods 2 and 3 in terms of structure and bonding.

Answer 20

Period 2

• Melting point increases up to C then falls dramatically from C to N
• Intermolecular bonds in nitrogen much weaker than in carbon

Period 3​

• Melting point increases up to Si then falls dramatically from Si to P
• Intermolecular bonds in phosphorous much weaker than in silicon

Question 21

Explain how the Geiger-Marsden experiment provided evidence for a small, dense nucleus.

Answer 21

• Alpha particle beam fired at thin sheet of gold foil. Expected to pass through or be slightly deflected
• Very few deflected at all
  
  • Concluded that most of atom is empty space
• Small number deflected backwards
  
  • Concluded that most of atom’s mass is concentrated in a small nucleus, which is +ve since it repelled +ve particles