Q154CP

Question

Nuclei differ in their stability, and some are so unstable that they undergo radioactive decay. The ratio of the number of neutrons to the number of protons (N/Z) in a nucleus correlates with its stability. Calculate the N/Z ratio for (a) 144Sm; (b) 56Fe; (c) 20Ne; (d) 107Ag. (e) The radioactive isotope 238U decays in a series of nuclear reactions that includes another uranium isotope, 234U, and three lead isotopes, 214Pb, 210Pb, and 206Pb. How many neutrons, protons, and electrons are in each of these five isotopes?

Step-by-Step Solution

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Answer
  1. The N/Z ratio of 144Sm is 1.32
  2. The N/Z ratio of 56Fe is 1.15
  3. The N/Z ratio of 20Ne is 1
  4. The N/Z ratio of 107Ag 1.28
  5. Each of the neutrons protons and electrons can be found.
1Step 1: Calculating the N/Z ratio for 144 Sm

Samarium has an atomic number of Z=62. Other numbers can be calculated as

 

Number of electrons= Number of protons(Z)

                                          =62   

Number of neutrons(N)=Mass number-atomic number

                                         N=144-Z   =144-62   =82 

                                      N/Z=82/62         =1.32

2Step 2: Calculating the N/Z ratio for 56 Fe

Iron has an atomic number of Z=26. On subtracting Z from the mass number,

 Number of electrons=Number of protons(Z)                                     =26Number of neutrons(N)=Mass number -atomic number                                      N=56-Z                                         =30                                   N/Z=30/26                                            =1.15

3Step 3: Calculating the N/Z ratio for 20 Ne

Neon has an atomic number of Z=10. On subtracting Z from the mass number,

 Number of electrons =Number of protons (Z)                                      =10Number of neutrons (N)= Mass number -atomic number                                      N=20-Z                                         =20-10                                         =10                                     N/Z=10/10                                            =1

4Step 4: Calculating the N/Z ratio for 107 Ag

Silver has an atomic number of Z=47. On subtracting Z from the mass number,

 Number of electrons =Number of protons (Z)=47Number of neutrons (N)= Mass number -atomic number                                      N=107-Z                                         =107-47                                         =60                                    N/Z=60/47                                            =1.28

5Step 5: Calculating neutrons, protons and electrons in each of the isotopes

Uranium (238U) has an atomic number of 92. The proton and electron amounts are equal. On solving for neutron number and then subtracting Z from mass number,

 Number of electrons =Number of protons (Z)                                       =92Number of neutrons (N)= Mass number -atomic number                                      N=238-Z                                         =238-92                                         =146                                    N/Z=60/47                                            =1.28

Uranium (234U) has an atomic number of 92. The proton and electron amounts are equal. On solving for neutron number and then subtracting Z from mass number,

 Number of electrons =Number of protons (Z)                                       =92Number of neutrons (N)= Mass number -atomic number                                      N=234-Z                                         =234-92                                         =142                                    N/Z=60/47                                            =1.28

Uranium (214Pb) has an atomic number of 82. The proton and electron amounts are equal. On solving for neutron number and then subtracting Z from mass number,

 Number of electrons =Number of protons (Z)                                       =82Number of neutrons (N)= Mass number -atomic number                                      N=214-Z                                         =214-82                                         =132                                           For210Pb                                       N=210-z                                          =210-82                                          =128                                         For206Pb                                        N=206-Z                                           =206-82                                           =124