Atomic Structure

Question 1

Quantum numbers? what does it give?
Number of subshells in a shell depends upon_______.

Answer 1

• The approach of expressing the presence of electrons around the nucleus in digital/mathematical way gave rise the concept of quantum numbers.
• specify the exact location of an electron in an atom.
• the shell no.
• bigger the shell, more are the no. of subshells in it & more electrons can be accommodated in it.

Question 2

first quantum number? represented by? what else does it give? value range? if value is greater _____?

Answer 2

The pqn (n) describes the energy level & size of an electron’s orbital in an atom
period no. in the periodic table
n= 1,2,3,4…
If n is greater, the energy of the shell is greater, so is its size.

Question 3

second quantum number? represented by? value range? determines? orbital?

Answer 3

• The azimuthal qn (l) describes the shapes of orbitals of electronic shells
• 0 to n-1
• Azimuthal qn determines the orbital’s angular momentum of the electron & specifies the subshell within a given principal energy level (n).
• a space around the nucleus where the probability of finding the electron is maximum.

Question 4

3rd quantum number?
represented by? value range? how to find the value?
find mqn for p orbital? what does it mean?

Answer 4

represented the orientation of orbitals
also gives no. of orbitals
-I to +l it means
m =….-3,-2,-1,0,+1,+2,+3,…
m= 2l + 1

l=azimuthal qn

these no. show that p oribital can be positioned in 3 different ways x y or z -1 0 +1

Question 5

4th quantum number
why electrons must have opposite spins?
represented by?

Answer 5

• Spin qn describe spin of an electron. (s)
• To reside in one orbital two electrons must cancel magnetic field of each other, for this purpose they have opposite spins.
• Clockwise spin represented by +1/2 ↓
• anticlockwise spin represented by-1/2 ↑.

Question 6

does an electron spin about its axis? who proved it?
orbital formed by magnetic qn?

Answer 6

yes Goudsmit in 1925
max. two electrons can reside in one orbital formed by magnetic qn.
two electrons in one orbital must have opposite spin, if one spins clockwise the other’s spin will be anti-clockwise.

Question 7

how can u relate quantum numbers to electronic config.?
2p explain this

Answer 7

a complete electronic config. must represent all the 4 quantum numbers
or
with the help of 4 quantum numbers one should be able to write the complete config.

Question 8

how is emission spectra used for electronic config.

Answer 8

• When atoms absorb energy, such as through heat or electricity, electrons move to a higher energy level.
• When these electrons return to their lower energy levels, they release the absorbed energy in the form of light.
• The emitted light can be analyzed to reveal the unique spectral lines or patterns of each element.
• This process is essential in spectroscopy & is widely used to identify & understand the electronic structure of atoms.

Question 9

how emission spectrum is used to determine electronic config.?
what does line spectrum consists of?
what does this indicate?

Answer 9

• Each element has a characteristic line spectrum consisting of certain wavelengths of light that is emitted when electrons move between energy levels.
• By analysing spectral lines in the emission spectrum, one can infer the energy levels & transitions that electrons undergo in an atom.
• The observation of distinct lines supports the Bohr’s idea that electrons occupy specific, quantized energy levels (shells).

Question 10

how is electronic config. deducted from spectral lines?

Answer 10

• The number & position of the lines in the spectrum can be used to determine the no. of shell electrons & the distribution of the shell electrons.
• For instance, the number & arrangement of lines in the spectrum indicates the number of major energy levels or shell electrons.

Question 11

example of emission spectrum?

Answer 11

• a H atom is an eg. Its emission spectrum is composed of distinct lines that represent the electron transitions in the H atom. It helps to determine the energy levels of H & its electronic config.
• Another eg is a Na atom. Na has a characteristic yellow emission line. Analyzing this line helps to determine sodium’s electronic config., including the distribution of electrons in the energy levels of Na.

Question 12

Auf Bau principle?
The increasing energy order of orbitals is?

Answer 12

Electrons are distributed in orbitals / subshells in order of increasing energy. Firstly, low energy orbitals are filled then electrons are filled in high energy orbitals.
1s < 2s < 2p < 3s < 3p < 4s < 3d

Question 13

3p < 4s < 3d? why?

Answer 13

Higher the n + I value, higher will be the the energy of the orbital.
e.g. n+l value for 4s orbital is 4+0 = 4 3d orbital is 3+2=5 so the energy of 3d orbital is greater than 4s orbital.

Question 14

pauli exclusion principle

Answer 14

No two electrons in an atom can have the same values of all the four quantum numbers, at least the spin quantum number will be different.
If two electrons are present in the same orbital (n,l and m are same) their spin will be opposite
for both. If one is clockwise(s=+1/2) ↑ the other will be anticlockwise(s=-1/2) ↓.

Question 15

Hund’s rule? example?

Answer 15

if degenerate orbitals (orbitals with equal energy) are available, the
electrons will tend to reside separately with same spin, instead of pairing up in the same orbital with opposite spin.

Question 16

Energy of orbital is related with _____________.
The energy of an orbital depends on?
Orbitals with __________ energies are filled before those with _______ energies.

Answer 16

• the number of electrons present in it. Half-filled & completely filled orbitals are more stable with less energy.
• its distance from the nucleus
• and the electron-electron repulsion it experiences.
• lower higher

Question 17

how to determine electronic config of atoms/ions with electron number & charge?
For cations, start with the neutral atom’s electron configuration and _______ electrons equal to the magnitude of positive charge from/to outermost shell to create the ion’s configuration.
what abt anions?

Answer 17

• Identify the neutral atom’s electron config.
• Determine the charge of the ion
• Write the electron config for the ion
• remove
• add

Question 18

The relationship between inter-electron repulsion and electronic configuration?
The repulsion between electrons ________ with the ________ in the number of electrons in the same orbital

Answer 18

• electrons tend to minimize repulsion by occupying their own separate orbital, rather than sharing an orbital with another electron.
• This is because electrons repel each other due to their identical charges, and this repulsion is minimized when electrons occupy separate orbitals in the same subshell.
  increases increase

Question 19

orbital? shape? lobes?

Answer 19

the region in space where the probability of finding an electron is max.
Different orbitals have different shapes in three-dimensional space.
s-orbital: s orbital is a spherical.
p-orbital: P orbital is dumbbell shaped
d-orbital: d orbital is cloverleaf shaped.
f-orbitals: They have complicated shapes.

Question 20

free radical? example?

Answer 20

an atom or molecule with an unpaired electron or electrons in its outer shell.
This makes it highly reactive and capable of immediate reactions. They are activated atoms or molecules. The electronic configuration of free radicals is the same as those of atoms.
For example: Cl, CH3, Br
For example, the electronic config. of chloride free radical is the same as that of chlorine atom, but they are shown by a dot on them.

Question 21

ionization energy?
why in this state?

Answer 21

The min. energy needed to remove the outermost electron (most loosely bonded electron) from the gaseous isolated atom.
Atom is needed to be in the gaseous state to avoid the influence of other factors like heat of fusion, bond dissociation energy, and heat of the vaporization.

Question 22

ionization energy ______ from left to right? why?

Answer 22

increases
* increase number of protons in each step which strengthen the attraction of nucleus on the electrons.
* Electronic config. also effects the ionization energy.
* Atomic radius decreases from left to right which brings the electrons near to the nucleus thus the attraction is increased and so does the ionization energy.

In group number IIIA less ionization energies are observed as there is only one electron
in p orbital which is an unstable configuration. Instead in group VA greater ionization energy
values are observed this is due to the half-filled p orbitals.

Question 23

In a group from
top to bottom the ionization energy _________.
if shielding effect decreases, I.E _______.
unit of I.E?

Answer 23

decreases
As the atom becomes bigger & the valence electrons go away from the nucleus, the shielding effect keeps on increasing so it is easier to remove the valance electron.
increases
KJ/mol

Question 24

Factors influencing the ionization energy?

Answer 24

4
Nuclear charge
Atomic radii
Shielding effect
Spin pair repulsion

Question 25

electron pair repulsion? how does it affect I.E?

Answer 25

* When electrons are paired in half filled p orbital there is electron pair repulsion which causes the energy of the electron to increase. * Increased energy makes the electron easier to remove and therefore the I.E decreases. * example, there is slight decrease in I.E in going from nitrogen to oxygen in the second period.

Question 26

Deduction of position of an element in the periodic table by using ionization energy data?

Answer 26

Trends in ionization energy Periodic table organization Comparing ionization energies

Question 27

The first, second, and third ionization energy values of magnesium in kJ/mol are as follows: First ionization energy: 735 kJ/mol Second ionization energy: 1445 kJ/mol Third ionization energy: 7730 kJ/mol deduce electronic config. and position in periodic table?

Answer 27

This indicates that the third electron is being removed from the inner shell. It indicates that there are only 2 electrons in the valence shell which are removed easily so this element should be a part of group number 2.

Question 28

mass spectrometry?

Answer 28

* a powerful analytical technique used to determine the molecular composition & structure of a sample by measuring the mass-to-charge ratio of ions. * involves 3 steps: ionization, mass analysis, and detection. * The sample is first ionized, converting its molecules or atoms into charged ions. * These ions are then separated based on their mass-to-charge ratio (m/z) and detected to generate a mass spectrum, which provides information about the composition and abundance of the sample's molecule or isotopic composition of an element

Question 29

working of mass spectrometer? how is the sample ionized? what is the purpose of mass analyzer? what is the detector?

Answer 29

lonization: The sample is introduced into the ion source where it is ionized. This process can involve bombarding the sample with high-energy electrons (El), introducing it to a high-voltage field (ESI), or using a laser to vaporize it Matrix Assisted Laser Desorption /lonization (MALDI). lon Separation: The resulting ions are then accelerated and directed into the mass analyzer. The mass analyzer separates ions based on their m/z ratio, allowing ions of different masses to be focused and detected at different times. Detection: As the ions exit the mass analyzer, they hit the detector. The detector records the time it takes for each ion to reach it, and this data is used to calculate the m/z ratio of each ion.

Question 30

what is mass spectrum?

Answer 30

* The information collected from the detector is used to construct a mass spectrum. * The x-axis of the spectrum represents the m/z ratio, while the y-axis represents the abundance of ions at each m/z ratio. * Peaks in the spectrum correspond to different ions present in the sample, with their positions revealing their masses.

Question 31

applications of mass spectrometry?

Answer 31

including relative abundance of isotopes of an element, identifying unknown compounds, quantifying the amounts of specific substances, elucidating molecular structures, and studying biomolecules like proteins and nucleic acids.

Question 32

avg. atomic mass formula Cl has realtive atomic mass 35.48 amu? what does this mean

Answer 32

Average atomic mass=(Mass No. x relative abundance)+(Mass No. x relative abundance)+... divided by 100 | 1 mole of chlorine atoms (6.022 × 10²³ atoms) has a mass of 35.45 grams.

Question 33

why _____ are non integral numbers? Cl has realtive atomic mass 35.48 amu? what does this mean

Answer 33

* atomic masses * the result of the inclusion of relative abundance of different isotopes of an element. * 35.48 means that in any natural sample of chlorine, the average mass of an atom is 35.48 times the mass of 1/12th a carbon-12 atom. | * 1 mole of chlorine atoms (6.022 × 10²³ atoms) has a mass of 35.45 gram

Question 34

what is excitation? electronic config. of Silicon? what's valence & conduction bands?

Answer 34

due to the relatively small energy gap b/w the valence & conduction bands (referred to as the band gap), electrons can be promoted from the valence band to the conduction band, creating electron-hole pairs. This process is called excitation. ## Footnote si Z= 14 valence electrons=4

Question 35

Semi-conductors can be intrinsic or extrinsic? explain. dopants? doping?

Answer 35

Intrinsic semiconductors are pure materials like silicon or germanium, while extrinsic semiconductors have controlled impurities intentionally added. These impurities are called dopants and can either introduce extra electrons (n-type) or create "holes" that behave like positive charge carriers (p-type). This process is known as doping & is achieved by substituting some silicon atoms with other elements like phosphorus (for n-type) or boron (for p-type).

Question 36

how can silicon be both n type and p type

Answer 36

The special electronic configuration of silicon makes it able to either accept or lose the electron, so silicon can work as n-type or p-type semi-conductor depending on the doping agent. For example, if Si is doped with P, silicon will be n-type (electron accepter) while doping with elements like Boron makes Silicon p-type (electron donor) semi-conductor.

Question 37

n-type & p-type semiconductors? applications?