Question

Find to three significant digits the charge and the mass of the following particles. Suggestion: Begin by looking up the mass of a neutral atom on the periodic table of elements in Appendix C of the textbook.

Answer 1

8) for doubly ionized calcium atom, Ca++ = Ca2+ :

       mass = mass of calcium atom - (2)(mass of electron)

               = (40)(1.67*10^-27 kg) - (2)(9.11*10^-31 kg)

               = 6.68*10^-26 kg

               = (6.68*10^-26)(1/1.66*10^-27) u

               = 40.2 u

9)

ammonia molecule (N^3-) :

   charge = (3)(charge of electron)

              = (3)(-1.6*10^-19 C)

              = -4.8*10^-19 C

              = -480 zC

10) mass = mass of N atom + (3)(mass of electron)

             = (14)(1.67*10^-27 kg) + (3)(9.11*10^-31 kg)

            = 2.34*10^-26 kg

            = 14 u

11)

for N⁴⁺ :

    charge = charge of four protons

               = (4)(1.6*10^-19 C)

                =6.4*10^-19 C

               = 640 zC

12) mass = mass of nitrogen atom - (4)(mass of electron)

            = (14)(1.67*10^-27 kg) - (4)(9.11*10^-31 kg)

            = 2.34*10^-26 kg

            = 14 u

13)

for nucleus of a nitrogen atom (N₇⁷) :

it has seven protons and seven neutrons.

           charge = (7)(charge of proton)

                      = (7)(1.6*10^-19 C)

                      = 11.2*10^-19 C

                      = 1.12*10^-18 C

                     = 1.12 aC

14) mass = mass of the nitrogen atom - (7)(mass of electron)

                    = (14)(1.67*10^-27 kg) - (7)(9.11*10^-31 kg)

                    = 2.34*10^-26 kg

                    = 14 u

15)

for molecular ion H₂O^- :

         charge = charge of electron

                    = -1.6*10^-19 C

                    = -160 zC

16) mass = mass of H2O molecule + (1)(mass of electron)

                  = (18)(1.67*10^-27 kg) + (1)(9.11*10^-31 kg)

                 = 3.01*10^-26 kg

                 = 18.1 u