All Students Notes

Question 2.9: State Heisenberg's uncertainty principle. Answer. It states that it is impossible to determine the exact position and momentum of electron simultaneously with absolute precision. If we determine one value with more accuracy, then second value is determined with less accuracy and vice versa. Question 2.10:  Why is 4s orbital lower in energy than 3d orbital? Answer Energy of an orbital can be determined using  n + ℓ rule or Wiswesser's  rule.  According to  this rule, orbital with lower   n + ℓ value has lower energy than orbital with higher  n + ℓ value. For  4s orbital, n =4 and   ℓ  = 0, so its  n + ℓ  (i.e.,  n + ℓ = 4 + 0 = 4) value is 4 while for 3d orbital,  n =3 and   ℓ  = 2, so its  n + ℓ value  (i.e.,  n + ℓ = 3 + 2 = 5) is 5 . Therefore, 4s orbital has lower energy than 3d orbital. Question 2.11: What is  n +   ℓ rule? Answer. According to this rule, ...

Question 2.5. What is the relationship between a. Energy and wavelength?  The energy of radiation is inversely proportional to its wavelength  E = hc/ λ E = Energy of radiation λ = wave length of any light radiation  h = Plank's constant  (b)  Frequency and wavelength  Frequency is inversely related to wavelength  c = v λ  ν  = c/ λ Where c = velocity of light  λ = wave length of any light radiation  ν  = frequency of light radiation  Question 2.6: What species are formed by decay of neutron?  Answer. Generally neutrons are stable in most of nuclei. However, a free neutron has short half life and decays into a proton, an electron and an antineutrino.  Question 2.7: Hydrogen atom and He+ are mono electronic system, but the size of He+ is much smaller than H, why? Answer Size of  He+ is much smaller than H, because nuclear charge of He+ is twice as greater as  the nuclear charge of H atom. Although,...

  Question 1.3.  Which quantum number is also called sub-shell quantum number? Answer .  Azimuthal quantum number is also called subshell quantum number as it describes the shape of an orbital or sub-shell. It is denoted by "   ℓ". Its numerical values are 0,1,2,3...n-1. For s - subshell or orbital    ℓ  = 0 For p - subshell or orbital    ℓ  = 1 For d - subshell or orbital    ℓ  = 2 For f - subshell or orbital    ℓ  = 3 Question 3.4  What is the difference between an orbit and orbital?  Answer.  Orbit Orbit may be defined as  "The circular path in which electron revolves around the nucleus of an atom". It is also represented by K, L, M, N,... It has two dimensional circular planer shape.  It is used to calculate the radius of atom and energy of electron in Bohr atomic theory. An orbit can accommodate maximum 2n2 electrons.  Orbital Orbital may be defined as The space around the ...

Question 2.1 How mass of electron can be calculated from e/m ratio and charge?  Answer . As we know that  Charge to mass ratio of electron = e/m                               = 1.7588 E11 coulomb /Kg Charge on electron  = e                                   = 1.6022 E-19 coulomb  So,  (1.6022 E-19 C) /m = 1.7588 E11 C /Kg or (1.6022 E-19 C) / 1.7588 E11  C/Kg = m  9.1095 E-31 Kg = m Question 2.2. How does Moseley's law help in production of X-rays? Answer. Mosley'law states that The frequency of a spectral line in a X-rays varies as square of atomic number of element emitting it. Or Mathematically,  Where a and b are constants for one type of x-rays and independent of metal used.  By this law, it is possible to produce X-rays of desired frequency and wave length by selecting a me...