Constituents of the atom and isotopesAQA A-Level Physics: Subtopic test

1. 1
   A student studies the structure of lithium. A neutral atom of lithium-7 is written $^{7}_{3}\mathrm{Li}$. Use e = 1.60×10⁻¹⁹ C.

   (a)

   How many nucleons are there in the nucleus of a $^{7}_{3}\mathrm{Li}$ atom?

   [1 mark]

   • A7
   • B3
   • C4
   • D10

   (b)

   The lithium atom loses one electron to form a Li⁺ ion. What is the charge on the ion?

   [1 mark]

   • A+4.80×10⁻¹⁹ C
   • B+1.60×10⁻¹⁹ C
   • C−1.60×10⁻¹⁹ C
   • D0 C

   (c)

   Another isotope of lithium is $^{6}_{3}\mathrm{Li}$. State the number of protons, neutrons and electrons in a neutral atom of this isotope.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Chlorine, proton number 17, occurs naturally as two stable isotopes, chlorine-35 and chlorine-37. In sodium chloride chlorine forms chloride ions, Cl⁻.

   (a)

   How many electrons are there in a $^{35}_{17}\mathrm{Cl}^{-}$ ion?

   [1 mark]

   • A17
   • B16
   • C18
   • D35

   (b)

   Which pair of nuclides are isotopes of the same element?

   [1 mark]

   • A$^{24}_{12}\mathrm{Mg}$ and $^{24}_{11}\mathrm{Na}$
   • B$^{14}_{6}\mathrm{C}$ and $^{14}_{7}\mathrm{N}$
   • C$^{16}_{8}\mathrm{O}$ and $^{17}_{9}\mathrm{F}$
   • D$^{12}_{6}\mathrm{C}$ and $^{13}_{6}\mathrm{C}$

   (c)

   State one way in which atoms of chlorine-35 and chlorine-37 are the same and one way in which they differ, in terms of particles.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Naturally occurring chlorine consists of 75.8% chlorine-35 and 24.2% chlorine-37 by number of atoms. Use e = 1.60×10⁻¹⁹ C and take the mass of a nucleus to be the number of nucleons multiplied by 1.67×10⁻²⁷ kg.

   (a)

   Calculate the relative atomic mass of naturally occurring chlorine.

   [3 marks]

   (b)

   Calculate the specific charge of a chlorine-35 nucleus.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Physicists use the specific charge of particles to predict how they move in electric and magnetic fields. Use e = 1.60×10⁻¹⁹ C, proton mass 1.67×10⁻²⁷ kg and electron mass 9.11×10⁻³¹ kg. The mass of a ³He nucleus is 5.01×10⁻²⁷ kg and the mass of a ⁴He nucleus is 6.64×10⁻²⁷ kg.

   (a)

   Calculate the specific charge of a proton and of an electron, and explain why the values are so different.

   [6 marks]

   (b)

   The nuclei of helium-3 and helium-4 are isotopes. Calculate the specific charge of each nucleus and explain why they are different even though the nuclei have the same charge.

   [6 marks]

   Total for question 4: 12 marks

End of questions