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chemistry class 11 > Structure Of Atom > Flashcards

Structure Of Atom Flashcards

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1
Q

-ve electrode

A

Cathode

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2
Q

Cathode rays are

A

deflects towards +ve plate
Travel in straight lines(absence of Elec field)
From cathode to anode
Not visible
In the presence of elec/mag field, the behavior is similar to -ve charged particles called electrons
Don’t depend on material of electrode or nature of gas

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3
Q

Amount of deviation of particles depend on

A

Greater the magnitude of-ve charge, more deflection
Lighter the particle more deflection
Strength of elec/mag field, increase in voltage increase deflection

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4
Q

Mass of electron

A

M(e) = 9.1 × 10^-31kg

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5
Q

Anode rays

A

E/m ratio Depends on nature of gas
+vely charged particles
Behavior in mag/elec field is opposite to cathode rays

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6
Q

Smallest and lightest +ve ion

A

Proton

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7
Q

Thomson’s model of atom

A

Atom is of spherical shape
+ve charge is evenly distributed
E’s are embedded into it to give it the most stable electrostatic arrangement
Called plum pudding model

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8
Q

Ruthaford’s nuclear model

A

+ve charge & mass of atom was densely concentrated in small region called nucleus
Nucleus is surrounded by e’s that move with high speed in orbits
E’s and nucleus are held together by electrostatic forces of attraction

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9
Q

Ruthaford Alpha particle scattering Expt.

A

Most of the particles passed w/o deflection
Small fraction of them deflected by small angles
Few particles deflected 180°
Conclusion:
Most of the space in atom is empty
Deflection mist be due to repulsive force showing that +ve charge is spread throughout the atom
small angles showed the presence of heavy center called nucleus.
Volume of nucleus is very small as that of atom

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10
Q

Atomic no Z =

A

No. of protons = no. of e’s

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11
Q

Mass no A=

A

No of protons(Z) + No of neutrons(n)

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12
Q

Isobars vs isotopes

A

Same mass no diff atom no
Same atom no diff mass no

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13
Q

Drawbacks of ruthaford’s model(alpha)

A
  1. Cannot explain stability of atom by Maxwell
  2. Can’t explain distribution of e’s around nucleus & energies of e’s
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14
Q

Electromagnetic theory of Maxwell

A

Maxwell said charged particles when accelerated should emit radiation, so the orbit will shrink and make the ‘e’ to spiral to the nucleus

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15
Q

Dev leading to Bohr’s model

A
  1. Dual char of radiation: wave & particle nature
  2. Atomic spectra
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16
Q

mass of proton

A

1.673 x 10^-27 kg

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17
Q

characteristics of waves

A

wavelength
frequency
velocity
amplitude
wave number

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18
Q

frequency of a wave is

A

no of waves which pass through a point in 1s

19
Q

velocity of a wave is

A

distance travelled by wave in 1s

20
Q

Limits of electromagnetic wave theory

A
  1. black body radiation
  2. Photoelectric effect
  3. Variation of heat capacity of solid as a function of temperature
  4. Line spectra of H
21
Q

Black Body Radiation

A

Ideal body, which emits and absorbs all frequencies. Frequency distribution depends only on its temperature.

22
Q

Plank’s Quantum theory

A

i) The radiant energy emitted or absorbed in the form of small packets of energy. Each such packets of energy is called a quantum.
(ii) The energy of each quantum is directly proportional to frequency of radiation

23
Q

photoelectric effect

A

phenomenon of when a beam of light of certain frequency strikes the surface of some metals, electrons are emitted or ejected from the metal surface

24
Q

Observations in Photoelectric Effect

A

(i) Only photons of light of certain minimum frequency called threshold frequency (v0) can cause it.
(ii) The kinetic energy of the electrons which are emitted is directly proportional to the frequency of the striking photons and is independent of their intensity.
(iii) The number of electrons that are ejected per second from the metal surface depends upon the intensity of the striking photons or radiations

25
Q

Explanation of Photoelectric Effect

A

(i) Photoelectrons are ejected only when the incident light has a certain minimum frequency (threshold frequency v0)
(ii) If the frequency of the incident light (v) is more than the threshold frequency (v0), the excess energy (hv – hv0) is imparted to the electron as kinetic energy.
(iii) On increasing the intensity of light, more electrons are ejected but the energies of the electrons are not altered.

26
Q

red colour which has _______ wavelength

A

longest

27
Q

Continuous Spectrum

A

When a ray of white light passing through a prism splits up into seven different wide bands of colours from violet to red (like rainbow). These colours are so continuous that each of them merges into the next.

28
Q

Line Spectra

A

When vapours of some volatile substance fall on flame of a Bunsen burner and analysed with spectroscope. Some specific coloured lines appear on the photographic plate which are different for different substances.

29
Q

Absorption Spectra

A

When white light is passed through the vapours of a substance and the transmitted light is then allowed to strike a prism, dark lines appear in the continuous spectrum. It indicates that the radiations were absorbed by the substance from white light.
Dark lines appear exactly at the same positions where the lines in the emission spectra appear.

30
Q

Line Spectrum of Hydrogen

A

When electric discharge is passed through hydrogen gas enclosed in discharge tube under low pressure and the emitted light is analysed by a spectroscope, the spectrum consists of a large number of lines which are grouped into different series known as hydrogen spectrum.
v’ = 109,677(1/n1^2 - 1/n2^2)/cm
RH = Rydberg constant for hydrogen and n2 > n1
For Lyman series, n1= 1, n2= 2, 3, 4, 5………..
For Balmer series, n1 = 2, n2 = 3, 4, 5, 6………..
For Paschen series, n1= 3, n2 = 4, 5, 6, 7………..
For Brackett series,n1 = 4, n2 = 5, 6, 7, 8………..
For Pjund series, n1 =5, n2 = 6, 7, 8, 9………..

31
Q

rydburg’s formula

A

1/lambda = v’ = R x Z^2(1/n1^2 - 1/n2^2)

32
Q

Bohr’s model

A

In an atom, the electrons revolve around the nucleus in certain definite circular paths called orbits.
(ii) Each orbit is associated with definite energy and therefore these are known as energy
levels or energy shells. These are numbered as 1, 2, 3… or K, L, M, N..
(iii) Only those energy orbits are permitted for the electron in which angular momentum of the electron is a whole number multiple of (h/2π)
(iv) As long as electron is present in a particular orbit, it neither absorbs nor loses energy
(v) When energy is supplied to an electron, it absorbs energy only in fixed amounts and jumps to higher energy state away from the nucleus known as excited state. The excited state is unstable, the electron may jump back to the lower energy state and in doing so, it emits the same amount of energy.

33
Q

Achievements of Bohr’s Theory

A
  1. Explained the stability of an atom.
  2. Helped in calculating energy of electron
34
Q

Limitations of Bohr’s Model

A

(i) could not explain atomic spectra of multielectron atoms.
(ii) failed to explain splitting of spectral lines in presence of magentic/electric field.
(iii) failed to explain the ability of atoms to form molecule formed by chemical bonds
(iv) failed to explain 3D model of atom and shapes

35
Q

de Broglie Equation

A

lambda = h/mc

36
Q

Heisenberg’s Uncertainty Principle

A

It is impossible to determine simultaneously, the exact position and exact momentum (or velocity) of an e’
delta V . delta x = (h/4pi)m

37
Q

h value

A

6.626 x 10^-34 Js

38
Q

a body can emit or radiate energy only in terms of

A

nh nyu

39
Q

Paschen, Brackett and Pfund has

A

Infra red lines

40
Q

lyman has

A

UV lines

41
Q

Balmer has

A

visible line

42
Q

E(n) energy of H atom

A

-2.18 x 10^-18/n^2 J/atom

43
Q

radius of nth orbit

A

r(n)=a(0).n^2 where a(0)=52.9pm

44
Q

velocity of e’ in nth orbit

A

V=V(o)/n
V= V(o)/n .Z
V(o)=2.188x10^8 cm/s

chemistry class 11 (9 decks)

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