Atomic Structure

Question 1

Describe s orbital

Answer 1

1. Spherical shape 2.non-directional,electron density not concentrated in any particular direction 3. As n increases, the orbital becomes more diffuse

Question 2

Describe p orbital

Answer 2

I’ dumbbell shape 2. 3 types: Px, Py and Pz 3. Directional: electron density concentrated along x, Y, z 4. All p orbitals have the same energy level 4. As n increases, the orbital becomes larger and more diffuse

Question 3

What does a signify

Answer 3

. N = principal quantum number

Question 4

Define atomic radius

Answer 4

Half the shortest inter-nuclear distancefound in the structure of the element

Question 5

Trend in atomic radii acrossa period

Answer 5

Trend: decreases
explanation: across aperod, numberof electron shells remain constant, number of protons increases, hence nuclearcharge increases and shielding effect remains approximately constant
Link: esfoa between nucleus and the valence electrons increases so there is a decrease in cloud size

Question 6

Trendin atomic radii down a group

Answer 6

• Trend: increases
  Explanation: number of electron shells increases, so distance between nucleus and valence electrons increases and shielding experienced by the valence electrons increases
  Link: despite increasing nuclear charge, ESFOA between nucleus and the valence electrons decreases, resulting in an increase in the size of the electron cloud

Question 7

why is the radius of a cation always smaller than that of the parent atom

Answer 7

same nuclear charge: both cation and the parent atom have the same number of protons
shielding: cation has one less electron shell than its parent atom, so its outermost electrons are shielded to a smaller extent
link: electrostatic attraction between nucleus and outermost electrons is stronger in cation, resulting in cation having a smaller electron cloud and smaller radis

Question 8

why is the radius of the anion always greater than that of the parent atom

Answer 8

same nuclear charge: both anion and parent atom have same number of protons
shielding effect increases: anion has more electrons than parent atom and with more electrons, shielding effect increases
link: electrostatic attraction btwn nucleus and outermost is weaker in the anion, so the anion has a larger electron cloud and a greater radius

Question 9

why does ionic radii of isoelectronic species decrease across a period

Answer 9

isoelectronic species are species with the same total number of electrons, so their outermost electrons experience the same shielding effect
across a period, number of protons increase so nuclear charge increases
electrostatic attraction between the nucleus and the outermost electrons increases across a period, resulting in the decrease in the size of the electron cloud

Question 10

why is there a sharp increase in ionic radius from Al3+ to P3-

Answer 10

Al3+: 1s2 2s2 2p6, P3-: 1s2 2s2 2s6 3s2 3p6
from Al3+ to P3-, the number of electron shells increase, so distance between the nucleus and the outermost electrons increases and the shielding experienced by outermost electrons increase
despite increasing nuclear charge, ESFOA between nucleus and the outermost electrons decreases, so the size of the electron cloud increases

Question 11

why is there an increase in first ionisation energies across a period

Answer 11

the number of electron shells remains the same
the number of protons increases so the nuclear charge increases
shielding effect remains approximately constant
ESFOA between the nucleus and valence electrons increases, resulting in an increase in energy required to remove the valence electron from an atom

Question 12

why is there a irregularity in first ionisation energy between elements of group 2 and group 13 in the same period

Answer 12

the first IE of Al is lower than that of Mg
Mg: 1s2 2s2 2p6 3s2, Al: 1s2 2s2 2p6 3s2 3p1
the 3p electron to be removed from Al is at a higher energy level than 3s electron to be removed from Mg
less energy required to remove the 3p electron in Al than 3s electron in Mg

Question 13

why is there a irregularity in first ionisation energy between elements of group 15 and group 16 in the same period

Answer 13

first IE of the elements in group 16 is lower than than group 15 elements across a period

electron to be removed from group 16 element is a paired electron whereas electron to be removed from group 15 element is an unpaired electron
greater electron-electron repulsion between paired electrons in same orbital, less energy is required to remove paired electron than unpaired electron

Question 14

why do the first IEs of elements down a group decrease

Answer 14

number of electron shells increase
distance between nucleus and valence electrons increases
shielding experienced by valence electrons increases
despite increasing nuclear charge, ESFOA between nucleus and valence electrons decrease
decrease in energy required to remove a valence electron

Question 15

why is there an increase in successive ionisation energies of an element

Answer 15

same nuclear charge: number of protons remain the same
number of electrons decreases and shielding experienced by the remaining outermost electrons decreases
ESFOA between nucleus and remaining electrons increase
increase in energy required to remove each subsequent electron

Question 16

how can we deduce and explain number of valence electrons of an element by its successive ionisation energies

Answer 16

large jump in 2 consecutive IE
the precedent IE is the number of valence electrons
more energy is required to remove the subsequent electron from the element as the subsequenth electron is located in an inner electron shell, closer to nucleus and experiences less shielding, so stronger ESFOA to nucleus, requires more energy to remove

Question 17

why does electronegativity increase across a period

Answer 17

number of electron shells remains the same
nuclear charge increases as number of protons increase
shielding effect remains approximately constant
ESFOA between nucleus and bonding electrons increases

Question 18

why does electronegativity decrease down a group

Answer 18

number of electron shells increase, distance between nucleus and bonding electrons increase and shielding experienced by bonding electrons increase
despite increasing nuclear charge, ESFOA btwn nucleus and bonding electrons decrease