Atomic Structure Flashcards
What is the absolute charge of an electron?
Electron: -1.602 × 10^-19 C or -4.8 × 10^-10 esu
What is the absolute charge of a proton?
Proton: +1.602 × 10^-19 C or +4.8 × 10^-10 esu
What is the absolute charge of a neutron?
0
What is the absolute mass of an electron?
9.1 × 10^-31 kg
What is the absolute mass of a proton?
1.672 × 10^-27 kg
What is the absolute mass of a neutron?
1.675 × 10^-27 kg
What is the specific charge of an electron?
1.76 × 10^11 C/kg
What is the specific charge of a proton?
9.58×10^7 C/kg
What is the specific charge of a neutron?
0
Name the elements that have atomic numbers from 21 to 30
Science(Sc) Teacher(Ti) Very(V) Crazy(Cr) Man(Mn) Feed(Fe) Cow(Co) Nickel Copper Zinc
In Rutherford’s Alpha Ray Scattering Experiment what was the box containing the radioactive element made of? Why?
The box was made of Lead.
Lead is a good absorber of alpha rays, preventing their scattering into the surroundings.
In Rutherford’s Alpha Ray Scattering Experiment, which radioactive element was used? Why?
Radium was used.
Radium produces a relatively large amount of alpha radiations.
Name the 4 layers of Rutherford’s Alpha Ray Scattering Experiment
The Lead Box
The Lead Slit
The Gold Foil
The Screen containing ZnS coating
In Rutherford’s Alpha Ray Scattering Experiment, which element made the foil? Why? Give its atomic number.
Gold(Z - 79) was used since it is highly malleable - it was beaten into a sheet 0.00004 cm thick.
Observations of the Gold Foil Experiment
- Most Rays passed undeviated
- Few rays got deflected slightly
- Around 1 in 20,000 rays would retrace its path.
- Increasing the Z of the target element would increase deflection of the alpha particle as the number of protons would increase.
What is the radius of the nucleus of an atom? What is the radius of an atom? What is their relation?
Radius of the nucleus = 10^-13
Radius of the atom = 10^-8
Radius of the atom = 10^5 Radius of the nucleus
Compare the volume of the atom and its nucleus
Volume of a sphere is (4πr³)/3
So Volume of atom : Volume of nucleus = (R/r)³ = (10⁵)³ = 10¹⁵
Relationship between radius of nucleus and mass number
Radius of nucleus = R₀ × A⅓
R₀ = 1.33 × 10^-13 cm
What is the formula for force of attraction between 2 charges? Which law does it follow?
According to Coulomb’s Law:
F = K . q₁ q₂/ r²
Based on Coulomb’s Law what is the formula for PE?
PE = F × d
= K . q₁ q₂/ r² × r
= K . q₁ q₂/ r
As distance between charges increases, how does PE get affected?
Like Charges:
Greater the separation, lesser the PE
Unlike Charges:
Greater the separation, greater the PE
What is the formula for distance of closest approach of Alpha particle
PEᵢ + KEᵢ = PEբ + KEբ
at initial position, r = infinity, so PEᵢ = 0
at final position, v = 0, so KEբ = 0
therefore KEᵢ = PEբ
therefore rₘᵢₙ = K . q₁ q₂/ KEᵢ
What is the ratio of specific charge of proton to specific charge of Alpha particle?
specific charge = charge/mass
therefore proton : alpha particle
1/1 ÷ 2/4 = 2:1
Define a wave
A method of transport of energy without transfer of matter
Define amplitude
Height of a crest or depth of a trough
Define wavelength
Distance between two consecutive crests or troughs
Define frequency
Number of waves passing through a point in one second
Define time period
Time taken for one wave to cross a given point
Define speed of a wave
Distance traveled by a wave per unit time
Define wave number
Number of waves in a unit distance
Basic Formula for speed of a wave
c = f * λ
Postulates of Maxwell’s Theory
- Theory suggests wave nature
- When a charged particle moves, it creates a magnetic component and an electric component
- Electric component and magnetic component of the wave are perpendicular to each other and to the direction of propagation of the wave. Such waves are known as electromagnetic radiations
Name the Radiations in the Electromagnetic Spectrum in increasing order of Wavelength
- cosmic rays
- gamma rays
- x rays
- ultraviolet rays
- visible spectrum
- violet
- indigo
- blue
- green
- yellow
- orange
- red
- infrared rays
- microwave rays
- radiowave rays
What is the speed of electromagnetic radiations?
3 * 10^8 m/s
In what Medium do electromagnetic radiations propagate?
Do not require medium for propagation
Formula for Time Period of a wave
T = 1/v(frequency)
Formula for wave number
wave number = 1/λ(wavelength)
Formula for speed of wave(using wave number)
speed = (f)frequency/(v)wave number
Wave nature can explain
- Interference
- Diffraction
Wave nature cannot explain
- Black Body Radiation
- Photoelectric Effect
Postulates of Planck’s Quantum Theory
- Theory suggests particle nature for EMR
- According to the theory, thermally hot objects absorb or emit energy
- Energy is emitted or absorbed in the form of small packets or bundles known as quantum
Formula for Energy associated with each quantum
E = hf
where h is Planck’s constant and f is frequency of the quantum
Value of Planck’s constant
6.626 x 10^-34 J.s or 6.626 x 10^-27 erg.s
Formula for Energy of quantum in joules
E = hc/λ(in metres)
Energy of quantum in eV
1240/λ in nm
1 eV in Joules and erg
- 6 x 10^-19 J
1. 6 x 10^-12 erg
Centripetal Force of an Electron
F = K[q1 x q2]/r^2 = K[Ze^2]/r^2
Centrifugal Force of Electron
mv^2/r
Formula for velocity of Electron from centripetal-centrifugal force
v^2 = K[Ze^2]/mr
From Bohr’s Model, Angular Momentum
mvr = nh/2π
Velocity of an Electron from Bohr’s Model
v = 2πZe²K/nh
Formula for Radius of an Electron
r = n^2h^2/4π^2Ze^2m*K
Numeric Formula for Radius of an Electron
r = 0.529 * n^2/Z angstrom
Proportionality for Radius of an Electron
r is directly proportional to n^2/Z
What is Photoelectric Effect?
When light(a photon) of a suitable frequency strikes a metal, it ejects an electron(known as photoelectron)
What is the threshold frequency of a photon?
The minimum frequency of a photon that allows for the emission of a photoelectron when it strikes a metal plate
Photoelectric Effect is exhibited by which elements?
Alkali Metals like Rb, Cs, K
How does voltage of the battery affect movement of photoelectron?
Higher the voltage if the battery, greater the chances of the photoelectron striking the anode
Formula for energy of a photon
Ephoton = hv
Formula for Threshold Energy of a photon
E = hvmin
If frequency of photon is less than threshold frequency
Photoelectron not emitted
If frequency of photon is equal to threshold frequency
Photoelectron emitted
If frequency of photon is more than threshold frequency
Photoelectron emitted with KE
Formula for energy of photon(in terms of charge and voltage)
Energy = Charge * Voltage
Formula for Charge of a photon
Charge = Current * Time
Formula for Energy of a Photon
E = Emin + KEphotoelectron
Threshold Energy for Li
2.4
Threshold Energy for Na
2.3
Threshold Energy for K
2.2
Threshold Energy for Mg
3.7
Threshold Energy for Cu
4.8
Threshold Energy for Pt
6.3
Formula for Intensity of Light
I = E/A*t
If intensity of light increases, what increases(from the formula)
Frequency of the photon remains constant
So only the number of photons can increase when intensity increases
The number of photoelectrons emitted is the same as
The number of photons incident
As intensity of light increases, photocurrent
Increases
Formula for stopping potential
V = KE/q
Numeric Formula for velocity of an electron in orbit
2.18 * 10⁶ * z/n metres per second
