Each question is followed by up to five lettered responses (A-E). For each question choose the response which is the best answer to the question.

1. The nucleus of an atom of  146C contains
   

   1.   ?    8 protons and 6 neutrons
   2.   ?    14 protons and 6 neutrons
   3.   ?    6 protons and 14 electrons
   4.   ?    6 protons and 14 neutrons
   5.   ?    6 protons and 8 neutrons

2. The nucleus of an atom of  188O contains
   

   1.   ?    10 protons and 8 neutrons
   2.   ?    8 protons and 10 neutrons
   3.   ?    8 protons and 18 electrons
   4.   ?    18 protons and 8 neutrons
   5.   ?    8 protons and 18 neutrons

3. Calculate the number of protons present in the nuclei of the atoms contained in 2.24 dm3 of nitrogen gas, N2 (atomic number of nitrogen is 7), at standard temperature and pressure, given that one mole of gas under these conditions occupies 22.4 dm3 and the value of the Avogadro constant, L = 6.0 x 1023 mol-1.
   It equals

   1.   ?    8.4 x 1023
   2.   ?    4.2 x 1024
   3.   ?    6.0 x 1022
   4.   ?    4.2 x 1023
   5.   ?    8.4 x 1021

4. Which one of the following statements applies to atoms which are isotopes of the same element?
   

   1.   ?    The mass numbers are the same.
   2.   ?    The number of electrons outside the nucleus is the same.
   3.   ?    The sum of the number of protons and neutrons is the same.
   4.   ?    The sum of the number of electrons and neutrons is the same.

5. The relative atomic mass of an element is
   
   

   1.   ?     the mass of one atom of the element on the scale ¹²₆C=12
   2.   ?     the average of the relative isotopic masses on the scale ¹²₆C=12
   3.   ?    the weighted average of the relative isotopic masses on the scale ¹²₆C=12
   4.   ?    the mass of 6 x 10²³ atoms of the element
      

6. Hydrogen has three isotopes, protium with no neutrons, deuterium with one neutron and tritium with two neutrons. In a sample trapped in a meteorite, they are found to occur in the ratio 10: 1: 1.
   What is the relative atomic mass of the hydrogen in the sample?
   

   1.   ?    1.00
   2.   ?    1.25
   3.   ?    2.00
   4.   ?    1.50

7. Neon occurs as two isotopes of mass numbers 20 and 22. Its relative atomic mass is 20.2.
   What is the percentage of ²⁰Ne in naturally occurring neon?
   

   1.   ?    80
   2.   ?    20
   3.   ?    90
   4.   ?    10

8. The nucleus of a tritium atom, ³H, contains
   

   1.   ?    three protons
   2.   ?    three neutrons
   3.   ?    two neutrons and one proton
   4.   ?    two protons and one neutron

9. The isotopic composition of a certain element X is 80% ²⁴X, 10% ²⁵X and 10% ²⁶X.
   The relative-atomic mass of X is
   

   1.   ?    24.67
   2.   ?    24.33
   3.   ?    24.25
   4.   ?    24.30