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Engineering
135 Views   |  

The maximum KE of the photoelectron is found to be 6.63\times10^{-19}J, when the metal is irradiated with a radiation of frequency 2\times10^{15} H_{2} . The threshold frequency of the metal is about

  • Option 1)

    1\times10^{15}s^{-1}

  • Option 2)

    2\times10^{15}s^{-1}

  • Option 3)

    3\times10^{15}s^{-1}

  • Option 4)

    1.5\times10^{15}s^{-1}

 
As learnt in Photoelectric Effect - - wherein where m is the mass of the electron u is the velocity associated with the ejected electron. h is plank’s constant. v is frequency of photon, v0 is threshold frequency of metal.     maximum KE  threshold frequency   we have   Option 1) This solution is correct. Option 2) This solution is incorrect. Option 3) This solution is...
Engineering
128 Views   |  

The incorrect order of energy of following orbitals is

  • Option 1)

    3s < 3p < 4s < 4d

  • Option 2)

    5p < 5d < 5f < 6p

  • Option 3)

    7s < 5f < 6d < 7p

  • Option 4)

    4d < 5p < 6s < 4f < 5d

 
As we learned in concept Aufbau Principle - In the ground state of the atoms, the orbitals are filled in order of their increasing energies. - wherein    The order of energy of orbitals is determined by n+l where n= principal quantum number and l = azimuthal quantum number So, 6p = 6+1 = 7       5f = 5+3 = 8       5d = 5+2 = 7        5p = 5+1 = 6 Clearly, to state that 5p<5d<5f<6p is...
Engineering
77 Views   |  

The energy of one mole of photons of radiation whose frequency is 1\times 10^{14}Hz 

  • Option 1)

    39.85\times 10^{3}\:J/mol

  • Option 2)

    39.90 \times10^{3}\:KJ/mol

  • Option 3)

    398.5 \times10^{3}\:J/mol

  • Option 4)

    3.985 \times10^{6}\:J/mol

 
As we learned in concept The energy (E) of a quantum of radiation - Where h is plank’s constant and  is frequency -    E=hv Energy with one mole of photons = = = Option 1) This option is correct. Option 2) This option is incorrect. Option 3) This option is incorrect. Option 4) This option is incorrect.
Engineering
110 Views   |  

The elements X, Y, Z and J have the indicated electron configurations starting with the innermost shell. The most metallic element is:

  • Option 1)

    X = 2,8,3

  • Option 2)

    Y=2,8,8

  • Option 3)

    Z= 2, 8, 8, 1

  • Option 4)

    J = 2, 8, 8, 7

 
As we learned in concept Metals - –  Form metallic bonds. –  78% of all known elements. –  good conductor of heat & electricity. –  Malleable and ductile. -    When we look at electronic config of these elements, we find that Y is a noble gas and J is a halogen (non metal). Between X to Z, Zis an alkali metal an also it is lower down the group than X and metallic character increases down the...
Engineering
107 Views   |  

The element whose electronic configuration is 1s^{2}, 2s^{2}, 2p^{6}, 3s^{2} is

  • Option 1)

    Metalloid

  • Option 2)

    Metal

  • Option 3)

    Noble Gas

  • Option 4)

    Non-metal

 
As we discussed in concept S- Block elements - The elements of group 1 (alkali metal) and elements of group 2 (alkaline metal) which have ns1 and ns2 configuration belong to s-block elements. -    The element with configuration is in group 2 and period 3. It is called magnesium. Elements with this configuration attain noble gas config by losing 2 electrons in 3s arbital. Therefore it is a...
Engineering
241 Views   |  

The diameter of zinc atom is 2.6 Å. The total number of atoms present in a length of 1.6 cm if the zinc atoms are arranged side by side length-wise are

  • Option 1)

    6.15\times10^{9}

  • Option 2)

    2.6\times10^{9}

  • Option 3)

    2.6\times10^{8}

  • Option 4)

    6.15\times10^{7}

 
As we discussed in concept Atomic Radius - The distance from the centre of the nucleus to the outermost shell containing the electrons is called atomic radius.It can be measured by the spectroscopic method and by x-ray diffraction or electron diffraction techniques. -    Diameter = Length = No. of zinc atoms = Option 1) This option is incorrect. Option 2) This option is incorrect. Option...
Engineering
224 Views   |  

On going down to a main subgroup in the periodic table (example Li to Cs in IA or Be to Ba in IIA) the expected trend of change in atomic radius is a:

  • Option 1)

    Continuous decrease

  • Option 2)

    Continuous Increase

  • Option 3)

    Periodic One, an increase followed by a decrease

  • Option 4)

    Periodic One, a decrease followed by an increase

 
  Size of atom and ion in a group - In a group moving from top to the bottom the number of shell increases.So the atomic size increases. - wherein    Upon descending in a group from top to bottom the number of shells of electrons increases therely increasing the of the atoms. Option 1) Continuous decrease Incorrect Option 2) Continuous Increase Correct Option 3) Periodic One, an increase...
Engineering
163 Views   |  

Neutron is a fundamental particle carrying 

  • Option 1)

    A charge of +1 unit and a mass of 1 unit

  • Option 2)

    No charge and no mass

  • Option 3)

    No charge and a mass of 1 unit

  • Option 4)

    A charge of -1 and a mass of 1 unit

 
As we learned in concept Discovery of Neutron - Rutherford in 1920 predicted the existance of a neutral fundamental particle chadwick bormbarded the element Beryllium with particle and noticed the emission of a neutral particle, later named as neutron. -    Neutron is a particle carrying no charge and a mass of 1 unit. Option 1) A charge of +1 unit and a mass of 1 unit Incorrect Option 2) No...
Engineering
144 Views   |  

Isobars are the atoms

  • Option 1)

    Some mass numbers but different atomic number

  • Option 2)

    Some atomic number but different mass number

  • Option 3)

    Some atomic number and mass number

  • Option 4)

    Different atomic number and mass number

 
As we learned in concept Isobars - Atoms with same mass number but different atomic number -    Isobars are atoms with same mass number, different atomic numbers. Option 1) Some mass numbers but different atomic number Correct Option 2) Some atomic number but different mass number Incorrect Option 3) Some atomic number and mass number Incorrect Option 4) Different atomic number and mass...
Engineering
282 Views   |  

In the transition elements, the incoming electron occupies (n-1)d sublevel in preference to:

  • Option 1)

    np

  • Option 2)

    ns

  • Option 3)

    (n-1)d

  • Option 4)

    (n+1)s

 
As we learned in concept Aufbau Principle - In the ground state of the atoms, the orbitals are filled in order of their increasing energies. - wherein   According to  Aufbau principle the electrons are filled in the order of energy of the orbitals. The orbital that is filled after (n-1)d is np by order of energy. Option 1) np Correct Option 2) ns Incorrect Option 3) (n-1)d Incorrect Option...
Engineering
333 Views   |  

If a diagonal line is drawn in Mendeleev's periodic table from left to bottom right, the elements below the diagonal will be:

  • Option 1)

    Metals 

  • Option 2)

    Non-metals

  • Option 3)

    Metalloid

  • Option 4)

    Transition metals

 
As we learnt in Mendeleev's periodic table - Mendeleev arranged the 63 discovered elements in the periodic table in to 7 horizontal rows known as periods and vertical column is known as groups numbered 1 to 8. -    In the Mendeleev periodic table, the metallic character of metals increases down the group and decreases along the period. So, the metals occupy the bottom left corner part till the...
Engineering
136 Views   |  

Identify the pairs which are not of isotopes

(i)  _{6}^{12}\textrm{X}, \:_{6}^{13}\textrm{Y}

(ii) _{17}^{35}\textrm{X}, \:_{17}^{37}\textrm{Y}

(iii) _{6}^{14}\textrm{X}, \:_{7}^{14}\textrm{Y}

(iv) _{4}^{8}\textrm{X}, \:_{5}^{8}\textrm{Y}

  • Option 1)

    i and ii

  • Option 2)

    ii and iii

  • Option 3)

    iii and iv

  • Option 4)

    i and iv 

 
As we learnt in Isotopes - Atoms having same atomic number but different mass number. -    i) atomic number =6, mass numbers different  ii) atomic number =17, mass numbers different  iii) atomic number different, mass numbers different  iv) atomic number different, mass numbers different clearly iii & iv do not isotopes Option 1) i and ii Incorrect option Option 2) ii and iii Incorrect...
Engineering
98 Views   |  

Halogens are placed in same group because they:

  • Option 1)

    Are electronegative

  • Option 2)

    Are most reactive

  • Option 3)

    Are not metals

  • Option 4)

    Have 7 electrons in outermost orbit.

 
As we learnt in Modern periodic law - The physical and chemical properties of elements are periodic functions of their atomic number. -    In the modern periodic table, elements are so arranged that the elements in the same group have the same number of valence electrons. All halogens have 7 electrons in the outermost shell.   Option 1) Are electronegative This option is incorrect. Option...
Engineering
179 Views   |  

Gases begin to conduct electricity at low pressure because

  • Option 1)

    At low pressure gases turn to plasma

  • Option 2)

    Atoms break up into electrons and protons

  • Option 3)

    Electrons in atoms can move freely at low pressure

  • Option 4)

    Colliding electrons can acquire higher kinetic energy due to the increased mean free path leading to ionisation of atoms.

 
As we learnt in Photoelectric Effect - The electrons are ejected from the metal surface as soon as the beam of light of a particular frequency strikes the surface. -    Only high energy electrons can ionize electrons from gas atoms and for electrons to gain energy, they must have a long mean free path which is possible only when pressure is love.   Option 1) At low pressure gases turn to...
Engineering
337 Views   |  

Elements of group IB and IIB are called:

  • Option 1)

    Normal Elements

  • Option 2)

    Transition elements

  • Option 3)

    Alkaline earth metals 

  • Option 4)

    Alkali metals

 
As learnt in Periodic table - Periodic table is defined as the table which classifies all the elements in such a way that elements with similar properties are grouped together in the same vertical column and elements with dissimilar properties are separated from one another. -     Elements of group IB and IIB are called  all belong in the d block of elements and can also be called transition...
Engineering
698 Views   |  

An element X occurs in short period having configuration ns2 np1 . The formula and nature of its oxide are:

  • Option 1)

    X03 , basic

  • Option 2)

    XO3 ,acidic

  • Option 3)

    X2O3 , amphoteric

  • Option 4)

    X2O3, Basic

 
As we learned in concept Newland's Octaves Law - Arranged the element in increasing order of their atomic weight and found that every eighth element had properties similar to that of the first element. Law of Octave was found to be true upto calcium. -    An element having configuration ns2 np1 will show +3 OS and its oxide nature willbe that of its group i.e. Baron, Aluminium, etc. X2O3, and...
Engineering
102 Views   |  

An element R forms the highest oxide R_{2}O_{5} . R belong to

  • Option 1)

    4 group

  • Option 2)

    6 group

  • Option 3)

    5 group

  • Option 4)

    8th group

 
As we learned in concept Aufbau Principle - In the ground state of the atoms, the orbitals are filled in order of their increasing energies. - wherein    R2O5 , the oxidation state of R is +5 which means it must belong to the fifth group. Option 1) 4 group This option is incorrect. Option 2) 6 group This option is incorrect. Option 3) 5 group This option is correct. Option 4) 8th group This...
Engineering
94 Views   |  

An element has the configuration 1s^{2}, 2s^{2}, 2p^{6}, 3s^{2}, 3p^{2} : To which block in the long form of the periodic table, does this belong?

  • Option 1)

    s-block

  • Option 2)

    p-block

  • Option 3)

    d-block

  • Option 4)

    f-block

 

p block

Engineering
122 Views   |  

A reduction in atomic size with increase in atomic number is a characteristic of elements of:

  • Option 1)

    f-block

  • Option 2)

    radioactive series

  • Option 3)

    high atomic mass

  • Option 4)

    d-block

 
As we learned in concept Application of shielding effect - 1.  It has been used in explaining the inert pair effect. 2.  It has been used to explain the lanthanide and actinide contraction. -    Because of the shape of orbitals, the shielding effect of electrons is too little. This is called lanthanide contraction. As we move down the group, atomic charge increases but because of shielding...
Engineering
226 Views   |  

A photon of wavelength 6000 Å has an energy E. The wavelength of the photon of light which corresponds to an energy equal to 2E is

  • Option 1)

    300 Å

  • Option 2)

    3000 Å

  • Option 3)

    30 Å

  • Option 4)

    3 Å

 
As learnt The energy (E) of a quantum of radiation - Where h is plank’s constant and  is frequency -    AND     Speed of electromagnetic radiation - where frequency is (,pronounced as nu), wavelength is (λ) and velocity of light is(c)   -    We know, E= energy of a quantum of radiation h=plank's constant frequency of radiation and Now, Put in 2     Option 1) 300 Å Option is...
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