Chapter 7: Multi-Electron Species and Periodic Properties

Question 1

What does the one-electron wavefunction consider and ignore? (2)

Answer 1

• attraction between electrons and the nucleus is considered

- electron-electron repulsion is ignored

Question 2

Where is the electron repulsion greatest?

Answer 2

• it is greatest in the overlapping areas of the probability distributions between orbitals

Question 3

What does electron-electron repulsion depend on and what does it affect?

Answer 3

• depends on subshell (l)

- affects the energies of the subshells

Question 4

Does the energy formula from the one-electron species apply for multi-electron species?

Answer 4

• no longer applies and subshells will have different energies

Question 5

effective nucleur charge

Answer 5

• nuclear charge that the valence electron “feels”, Z_eff

Question 6

What is an approximation of Zeff`

Answer 6

Z - # of shielding electrons

Question 7

shielding electrons

Answer 7

• electrons that are not in the valence shell

Question 8

spin quantum number (4)

Answer 8

• m_s
• allowed values: +1/2 and -1/2
• concept of electron spin
• represented by half-headed arrows

Question 9

orbital diagram

Answer 9

• each orbital is represented by a horizontal line and electrons are shown as half arrows pointing up or down, name of the orbital is written beneath the line

Question 10

What does 1s^22s^1 tell us (2)

Answer 10

• two electrons in the 1s orbital

- one electron in the 2s orbital

Question 11

electron configuration

Answer 11

• the name of the orbital is followed by the # of electrons in the orbital superscript

Question 12

Aufbau principle (the “building up” principle) (2)

Answer 12

• filling the orbitals with electrons from the lowest energy first: in a ground-state-multi-electron atom or ion, the electrons always occupy the lowest energy orbitals first available
• a maximum of 2 electrons can occupy each orbital, as long as they have opposite spin quantum numbers

Question 13

Pauli exclusion principle

Answer 13

• no 2 electrons in an atom or ion may have the same 4 quantum numbers

Question 14

What 4 quantum numbers are multi-electron species dependent on?

Answer 14

• n, l, m_s, m_l

Question 15

Hund’s rule

Answer 15

• when orbitals that have the same energy are available, electrons occupy them singly with the same spin before being paired within an orbital

Question 16

denegerate

Answer 16

• when orbitals have the same energy

Question 17

What is the general procedure for writing electronic configurations of multi-electron species?

Answer 17

1. locate the element in the periodic table noting the period (n) the element is in and the block (s,p,d,f)
2. identify the noble gas in the previous period (n-1) and write its symbol in square brackets
3. starting from the left of the periodic table in period n, write the subshells and occupancies in order until the element is reached
4. for ionic species (of the s or p blocks), simply add to (for anions) or subtract from (cations) the configuration for the neutral atom

Question 18

What are the exceptions to the regular electron filling? (2) (pt1)

Answer 18

• 4s and 3d orbitals are close in energy and their relative energies can change depending upon the particular electronic configuration of a d-block atom
• chromium: more energetically favourable to have one electron in the 4s orbital and one electron in each of the five 3d orbitals than to have two electrons in the 4s orbital and four electrons in the five 3d orbitals
• copper: configuration of [Ar]4s^13d^10, rather than the expected [Ar]4s^23d^9

Question 19

What are the exceptions to the regular electron filling? (pt2)

Answer 19

• transition metal ions: when transition metals are ionized, the remaining electrons will be found in the d subshell of the valence shell
• for example Sc: [Ar]4s^23d^1, Sc[I] ion Sc+; [Ar]3d^2

Question 20

Excited state of a muti-electron species

Answer 20

• when a species violates either Aufbau principle and/or Hund’s rule

Question 21

Which electrons possess an overall magnetic moment?

Answer 21

• only species with unpaired electrons

Question 22

paramagnetic

Answer 22

• species with one or more unpaired electrons

Question 23

diamagnetic

Answer 23

• species with no unpaired electrons

Question 24

What can be explained by considering the effect of increasing nuclear charge (Z), which decreases total energy, and increasing electronic repulsion, which increases total energy, within atoms and ions

Answer 24

• atom and ion size, ionization energy, and electron affinity

Question 25

How does increasing nuclear charge (Z) affect energy?

Answer 25

• decreases total energy

Question 26

How does increasing electronic repulsion affect energy?

Answer 26

• increases total energy

Question 27

covalent radius

Answer 27

• estimate for radius which is applied to single-bonded homonuclear species

Question 28

ionic radius

Answer 28

• estimate made from the crystal lattice structure and uses crystallography measurements of distances between nuclei in crystal lattice

Question 29

van der waal radius

Answer 29

• uses distances between non-bonded atoms to estimate the boundary of an atom

Question 30

What happens to atomic radii as we move in the periodic table and why? (2)

Answer 30

• atomic radii decreases as we move from left to right because distributions shift closer to the nucleus as Z and Z_eff increase
• the number of shells (n) in a species affects the radius more than the nuclear charge Z: as you go down the periodic table, n increases and the atomic radius increases

Question 31

Are cations smaller or larger than the neutral atom and why? (2)

Answer 31

• cations experience less electron-electron repulsion (greater Z_eff) then neutral counterparts and removal of all valence shell electrons leaves core electrons in the inner (n-1) shell
• cations are smaller than neutral atoms

Question 32

Are anions smaller or larger than the neutral atom and why? (2)

Answer 32

• anions experience more electron-electron repulsion (smaller Z_eff) then corresponding neutral atoms
• anions are larger than neutral atoms

Question 33

Why is the atomic radius of Al have a greater atomic radius than Ga, breaking the trend?

Answer 33

• Ga has more protons(?) in 3d, 4d and 5d cells

Question 34

Is an input or output of energy needed to move an electron further from the nucleus?

Answer 34

• given that electrons are held to the nucleus by electrostatic forces of attraction, an input of energy is required

Question 35

ionization energy

Answer 35

• minimum energy required to remove a single electron from an atom, molecule, or ion in its gaseous state
• proportional to the magnitude of electrostatic attraction between the electron being removed and the nucleus, combined with the electrostatic repulsion from the remaining electrons

Question 36

why is ionization energy and electron affinities measured in the gaseous state?

Answer 36

• so that energy from interactions between species (liquid and solid) does not affect the measurement

Question 37

what is the trend of ionization energy as we move left to right on the periodic table and why?

Answer 37

• ionization energy generally increases
• valence orbitals are closer to the nucleus on the right side so the electrons feel a stronger force of attraction to the nucleus, with effective Z_eff, and require more energy to be ionized

Question 38

what is the trend of ionization energy as we move from top to bottom on the periodic table and why?

Answer 38

• generally decreases
• size of the atom increases from top to bottom because the energy of attraction between the nucleus, with effective Z_eff, and valence electrons is inversely proportional to the distance between them

Question 39

electron affinity

Answer 39

• energy change that results from the addition of a single electron to an atom or ion in its gaseous state

Question 40

Is an input or output of energy needed to move an electron closer to the nucleus?

Answer 40

• output or release of energy
• if an electron is added to the right side of the periodic table, it will feel a greater attraction to the nucleus because the orbital it will occupy is lower in energy so more energy is released on the right side when elements gain an electron

Question 41

What is the trend of electron affinity on the periodic table?

Answer 41

• electron affinity increases from left to right until the halogens as the noble gases have very low electron affinities
• electron affinity decreases going down the periodic table as the added electron will go into an orbital that is further away from the nucleus (higher in energy) and will experience a lower force of attraction