Unit 9

Question 1

Excited state electron location

Answer 1

in the excited state, the electron will have a higher probability of being found further from the nucleus

Question 2

Comparison of Coulombic interactions for a 1-electron and 3-electron atom

Answer 2

In one-electron, electron only interacts with nucleus (positively charged, attractive). In 3-electron, electrons interact with nucleus (positively charged, attraction) and interact with electrons (negatively charged, repulsion)

Question 3

Screening/Shielding

Answer 3

electrons interact with each other, atoms/ions are H-like but comparatively contracted depending on the degree of exposure to the nucleus

Question 4

Z*(eff)

Answer 4

-net/effective nuclear charge that is “felt” by an electron of interest
-the net positive charge pulling the electrons towards the nucleus
-the higher the pull of the valence electrons, the higher the effective nuclear charge

Question 5

Nuclear charge

Answer 5

Z(eff)= Z-S
Z= atomic number
S= shielding

Question 6

Electron shielding

Answer 6

-electrons with the same n do not screen/shield effectively
-core electrons screen valence effectively
-for orbitals with same n value, the greater the number of secondary maxima, the greater the ability to penetrate the core electron density, and higher Z* felt by valence electrons

Question 7

Graphing r^2R^2 (Radial Probability Density Plot)

Answer 7

-core electrons are in secondary maxima, with each n value being a maxima (descending in height)
-valence electrons are graphed, with increasing l value causing larger width and lower height
-2* maxima (n-l) are drawn within secondary maxima and increase in height and width, tells how much shielding occurs (how much orbital can penetrate core electron density)(the more peaks, the more an orbital can penetrate core)

Question 8

core vs valence electrons (shielding)

Answer 8

-Core: feel most of positive nuclear charge, are not screened effectively by valence, do not screen each other effectively, shield valence effectively, more core= lower Z* (more screening)
-Valence: do not screen core or each other effectively, most often at larger r outside of core, more 2* maxima correlates to less shielding (higher Z*)

Question 9

Z* trends in periodic table

Answer 9

-Z* increases left-right on PT (more protons are added, valence electrons do not shield effectively, so electrons feel greater positive charge)
-Z* increases top-bottom (more core orbitals are filled as n increases,

Question 10

Ionization Energy

Answer 10

-minimum energy required to remove/eject an electron from the highest energy occupied valence orbital in gaseous state
-farther electron is from nucleus, the easier to pull it away (opposite of atomic radius trend, closer the electron is to nucleus, the harder it is to eject)
-electron is ejected with 0 kinetic energy

Question 11

IE trends and calculations

Answer 11

-First IE:
-X(g) -> X+(g) + e-
-IE= -[-13.6eV(Z*^2/n^2)]
-Second IE:
-X+(g) -> X2+(g) + e-
-IE2> IE1 (removing electron leads to less screening, greater affinity of last electron to nucleus)
-IE increases left-right (En becomes more negative, requiring more energy to ionize), decreases top-bottom (En becomes less negative because n increases)

Question 12

Electron Affinity (EA)

Answer 12

-minimum energy required to detach/remove/eject the highest energy valence electron from X- (singly charged anion) in gaseous state
-how much an atom wants to gain an electron
-noble gases are exception
-amount of energy released when an atom gains an electron (electron’s negative charge causes overall energy level to lower)

Question 13

EA trends

Answer 13

-X-(g) -> X(g) + e-
-increases left-right (Z* increases, so element will hold onto electrons more), decreases top-bottom (n increases, En becomes less negative)

Question 14

Atomic radii

Answer 14

-distance of valence shell of electrons from nucleus when atom is neutral
-sizes of atoms are determined by the volumes occupied by their electrons

Question 15

Atomic radii trends

Answer 15

-atomic radius decreases left-right (Z* increases, meaning electrons feel greater positive attraction, total energy of orbital decreases, nucleus increases, and electrons contract more centrally)
-atomic radius increases top-bottom (n increases, more core electrons are added, total energy increases, spatial extent of orbital increases as well)

Question 16

n (quantum number)

Answer 16

the principal quantum number which describes the energy level and average distance of an electron from the nucleus in an orbital; essentially indicating the size of the orbital, with higher “n” values signifying larger orbitals further from the nucleus

Question 17

Ionic radii

Answer 17

-distance of valence shell of electrons from nucleus when atom is electrically charged
-when forming ion, Z* changes for every electron and Coulombic attraction to nucleus is affected
-electrons repel each other, making ionic radius larger
-ions with same electron configuration will have radii decrease as atomic number increases (O(2-) > F- > Ne > Na+ > Mg(2+))

Question 18

Ionic radii trends

Answer 18

Anion: Z* decreases, r(anion) > r(neutral)
Cation: Z* increases, r(cation)<r(neutral)

Question 19

Electronegativity

Answer 19

-the ability of an atom in a molecule to attract electrons to itself from neighboring atoms
-X= (IE + EA)/2
-noble gases are exceptions (do not readily form molecules)

Question 20

Electronegativity trends

Answer 20

-increases left-right
-deceases top-bottom
-follows trends of IE and EA

Question 21

Equation for Z*

Answer 21

Enl= -13.6eV(Z^2/n^2)
or
Enl= -2.18x10^-18J(Z^2/n^2)

Question 22

Equation for determining orbital energies

Answer 22

-KE= Eph - I Enl I