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atomic structure Flashcards

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1
Q

charge of an electron

A

1.6 x 10^-19 C

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2
Q

mass of an electron

A

9.1 x 10^-31 kg

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3
Q

Avagadro no.

A

6.023 x 10^23

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4
Q

mass of proton

A

1.672 x 10^-27 kg

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5
Q

mass of neutron

A

1.675 x 10^-27 kg

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6
Q

no. of protons =

A

atomic no.

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7
Q

no. of neutrons =

A

mass no. - atomic no.

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8
Q

mass no. =

A

no. of protons+no. of neutrons

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9
Q

what is a black body?

A

an ideal body that emits and absorbs radiations of all

frequencies.

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10
Q

what is an atomic orbital?

A

it is defined as three-dimensional space around the
nucleus, where the probability of finding electrons is
maximum.

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11
Q

what is the Zeeman effect?

A

the splitting of one spectral line in external magnetic

field into several fine lines.

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12
Q

what is the stark effect?

A

the splitting of one spectral line in external electric

field into several fine lines.

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13
Q

explain Pauli’s exclusion principle

A

no 2 electrons in an atom can have the same set of
all 4 quantum numbers.
OR
an orbital can accommodate a maximum of 2 electrons
only with the opposite spin.

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14
Q

what is the Aufbau principle?

A

in the ground state of atoms, the orbitals are filled with

electrons in the order of their increasing energies.

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15
Q

what is Hund’s rule?

A

in the degenerate orbitals pairing of electrons take place, when each orbital is filled with one electron.
OR
in the degenerate orbital, first, the orbitals are half-filled
and later paired up.

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16
Q

explain Heisenberg’s uncertainty principle?

A

it is impossible to determine the exact position and momentum of a fast-moving particle like an electron simultaneously and accurately.

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17
Q

how is an orbital possible?

A

an orbital is possible if the azimuthal quantum no.

is less than principal quantum no.

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18
Q

explain the particle nature of electromagnetic radiation

A

particle nature of electromagnetic radiation can be explained with the help of black body radiation. the atoms and molecules could emit and absorb radiation only in discrete quantities called quantum and not in a continuous manner.

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19
Q

what series of lines are absorbed in hydrogen spectra

A 
Lyman - ultraviolet 
Balmer - visible
Paschen - near-infrared 
Brackett - infrared
Pfund - far-infrared
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20
Q

what are the main features of the quantum mechanical model of an atom?

A
  1. energy of electron in atoms is quantised.
  2. the existence of quantised energy levels is a direct result of the wave properties of electrons.
  3. the path of an electron in an atom can never be determined or known accurately. therefore the probability of finding an electron arises.
  4. an atomic orbital wave function represents the state of an electron in an atom.
  5. the region around the nucleus where the probability of finding an electron is max is known as an orbital.
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21
Q

velocity of electron=

A

1.6 x 10^6 m/s

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22
Q

planck’s constant (h)=

A

6.625 x 10^-34

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23
Q

wavelength of the electron(lambda)=

A

4.55 x 10^-10 m

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24
Q

lambda=

A

h/mv

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25
Q

emission spectrum

A
  1. the spectra is formed when an electron jumps from higher orbits to lower orbits.
  2. it is formed due to the emission of energy in quanta.
  3. it contains bright lines on dark background.
  4. it is classified into 2 types: continuous and discontinuous.
26
Q

absorption spectrum

A
  1. the spectra is formed when an electron jumps from
    lower orbits to higher orbits.
  2. it is formed due to the absorption of energy in quanta.
  3. it contains dark lines on bright background.
  4. it’s not classified.
27
Q

orbit

A
  1. it is a circular path of electron revolving around the nucleus.
  2. it represents the two-dimensional motion of an electron.
  3. an orbit can accommodate 2n^2 electrons where n stands for orbit number.
  4. shape is circular.
  5. position and velocity of the electron at any instant can be found precisely.
28
Q

orbital

A
  1. it is a region around the nucleus where electron can be found.
  2. it represents the three-dimensional motion of an electron.
  3. an orbital can accommodate a max. of 2 electrons.
  4. shape may be spherical, dum-bell, etc
  5. it is not possible to find the position and velocity of an electron at an instant.
29
Q

explain photoelectric effect.

A

when a beam of light of a suitable wavelength is allowed to fall on the surface of the alkali metal. the electrons are emitted from the metal surface.

30
Q

hv (photoelectric effect)=

A

Wo+KE

31
Q

hv=

A

energy of incident photon

32
Q

Wo=

A

work function

33
Q

what is threshold energy

A

the min. energy req. to break the force of attraction b/w nucleus and electron.

34
Q

limitations of Bohr’s model of an atom

A
  1. it cannot explain the spectra of multi-electron species
  2. it cannot explain the formation of fine spectrum.
  3. it failed to explain Zeeman and stark effect.
  4. It failed to explain the dual nature of electrons.
  5. it is against Heisenberg’s principle.
  6. it could not explain the formation of chem bonds.
  7. it could not explain the ability of atoms to form molecules and the geometry and shape of molecules.
35
Q

how are quantum no.s n,l,m,s arrived?

A

the quantum no.s n l m s arrived from Schrodinger’s wave eq. quantum no.s are introduced to explain the main shell, subshell, orientation and spin of the electrons.

36
Q

principal quantum no.

A
  1. it was proposed by Neils Bohr and is denoted by n.
  2. the total no. of subshell for a given value of n=n
  3. the total no. of orbitals for a given value of n=n^2
  4. the max no. of electrons for a given value of n=2n^2
    SIGNIFICANCE: it indicates the size of an orbit and the energy of an electron.
37
Q

azimuthal quantum no.

A
  1. it was proposed by Sommerfeld and is denoted by l
  2. the value of l depends on n. the value of l are from 0 to (n-1)
  3. when l values are 0,1,2,3 the subshells are called as s,p,d,f
  4. the no. of subshells for a given value of n=n value
    SIGNIFICANCE: it indicates the shape of the orbital.
38
Q

magnetic quantum no.

A
  1. it was proposed by Lande and is denoted by m
  2. the values of m depends on l. the values of m are from -l to+l including 0.
  3. the total m values or orbitals in subshell=2l+1
  4. the no. of orbitals in s,p,d,f subshells are 1,3,5,7
  5. the no. of electrons in a subshell= 2(2l+1)
  6. the total no. of electrons in s,p,d,f subshells are 2,6,10,14
    SIGNIFICANCE: it indicates the orientation of orbital in space.
39
Q

rydbergs constant=

A

109677 cm-1

40
Q

what are the consequences that led to the development of the quantum mechanical model of an atom?

A

classical mechanical model of an atom deals with the motion of macroscopic objects. while quantum mechanics deals with the motion of microscopic objects. the microscopic objects exhibit dual nature. they possess particle and wave nature.

41
Q

spin quantum no.

A
  1. it was proposed by goudsmith and uhlenbeck and is denoted by s.
  2. it is independent. the values of s are +1/2 and -1/2
  3. if electrons revolve in a clockwise direction-spin is given as +1/2.
  4. if electrons revolve in an anti-clockwise direction-spin is given as -1/2
  5. the max no. of electrons in an orbital is 2
  6. the max no. of electrons present in s,p,d,f shells are 2,6,10,14.
    SIGNIFICANCE: it indicates the direction of spin of the electron.
42
Q

significance of dual behaviour particles

A
  1. according to de Broglie, every object in motion has a wave character. the wavelengths associated with ordinary objects are so short that is why their wave properties cannot be detected.
  2. the wavelengths associated with electrons and other subatomic particles can however be detected by experiments.
43
Q

what are the various ranges of electromagnetic radiation?

A

γ rays, X rays, UV light, IR, microwaves and radio waves are called electromagnetic radiations because they are made up of electric and magnetic fields propagating in perpendicular directions with one another.
electromagnetic radiations can have wave characteristics and no medium is req. for their propagation. they can travel through vacuum.

44
Q

wavelength def:

A

the distance b/w 2 neighbouring throughs and crests in a wave is known as wavelength

45
Q

frequency def

A

the no. of waves that pass through a given point in one sec is called frequency.

46
Q

wave no. def

A

the reciprocal of the wavelength is called wave no.

47
Q

amplitude def

A

the height of the crest and the depth of the through of a wave.

48
Q

velocity def

A

the dist. travelled by a wave in one sec is called its velocity

49
Q

atomic orbital define

A

the 3-dimensional space around the nucleus where the probability of finding the electron is max.

50
Q

explain the shape of s orbital

A

whenever l=0 the orbital is designated as S orbital. it is spherical in shape. when l=0 m is also 0. so S orbital has 1 orientation.

51
Q

explain the shape of the p orbital

A

whenever l=1 the orbital is designated as P orbital. it is dumbell in shape. when l=1 m values are -1, 0, +1. so P orbital has 3 orientations. px, py, pz

52
Q

explain the shape of the d orbital

A

whenever l=2 the orbital is designated as D orbital. it is double dumbell in shape. when l=2 m values are -2, -1, 0, +1, +2. so D orbital has 5 orientations. dxy, dyz, dzx, dx2-y2, dz2

53
Q

explain the shape of the f orbital

A

whenever l=3 the orbital is designated as F orbital. it is complicated in shape. when l=3 m values are -3 to+3. so F orbital has 7 orientations.

54
Q

explain the boundary surface of three 2p orbitals and five 3d orbitals

A

2p orbitals are 2px, 2py, 2pz
the shape of any 2p orbital is a dum-bell shape.
for 2p orbital n=2, l=1, m=-1, 0, +1
3d orbitals are dxy, dyz, dzx, dx2-y2, dz2
total no of orientations equal to 5 and 5 orbitals are possible.
for 3d orbital n=3, l=2, m= -2, -1, 0, +1, +2

55
Q

explain the reasons for the stability of completely filled and half-filled subshell

A

the completely filled and half-filled subshells are stable due to 2 reasons.
symmetrical distribution of electrons: the symmetry leads to stability. the completely filled or half-filled subshells have symmetrical distribution hence these are stable.
exchange energy: the stabilizing effect arises whenever 2 or more electrons with the same spin are present in the degenerate orbitals of a subshell. these electrons tend to exchange their positions and energy released due to this exchange is called exchange energy. the no. of exchanges that can take place is max. when a subshell is either half-filled or completely filled.

56
Q

hydrogen spectrum

A

the hydrogen spectrum is the simplest of all the atomic spectra. when hydrogen gas is subjected to electric discharge at low pressure, bright lines are emitted. when the light is passed through the prism hydrogen spectrum is obtained. it contains no. of group of lines that can be classified into various series. they are Lyman, Balmer, paschen, brackett, pfund.

57
Q

continuous spectrum def

A

the series of bands that forms a continuous rainbow of colours.

58
Q

discontinuous spectrum types

A
  1. line spectrum 2. band spectrum
59
Q

line spectrum

A
  1. the line spectrum has sharp, distinct, well-defined lines.
  2. the line spectrum is given by gaseous atoms and is also called an atomic spectrum.
  3. the line spectrum is due to the transition of electrons in an atom.
  4. the line spectrum is given by inert gases.
60
Q

band spectrum

A
  1. the band spectrum has many closed lines.
  2. the band spectrum is given by molecules and is also called a molecular spectrum.
  3. the band spectrum is due to vibrations and rotations of atoms in a molecule.
  4. the band spectrum is given by hot metals.

chemistry (2 decks)

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