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F321: Atoms, Bonds and Groups
Atoms, Isotopes and Relative Atomic Masses
70 Marks
1. Isotopes of europium have differences and similarities. (i) In terms of protons, neutrons and electrons, how is an atom of 151 Eu different from an atom of 153 Eu? ......................................................................................................................... ......................................................................................................................... [1]
(ii) In terms of protons, neutrons and electrons, how is an atom of 151 Eu similar to an atom of 153 Eu? ......................................................................................................................... ......................................................................................................................... [1] [Total 2 marks]
2. Europium, atomic number 63, is used in some television screens to highlight colours. A chemist analysed a sample of europium using mass spectrometry. The results are shown in the table below. isotope relative isotopic mass abundance (%) (^151) Eu 151.0 47. (^153) Eu 153.0 52.
(a) Define the term relative isotopic mass. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [2]
(b) Using the table above, calculate the relative atomic mass of the europium sample.Give your answer to two decimal places.
answer = ................................... [2] [Total 4 marks]
3. Carbon occurs in a wide range of compounds and is essential to living systems.
Two isotopes of carbon are 12 C and 13 C. (i) State what is meant by the term isotopes. ......................................................................................................................... ......................................................................................................................... [1] (ii) Isotopes of carbon have the same chemical properties. Explain why. ......................................................................................................................... ......................................................................................................................... [1] (iii) The 12 C isotope is used as the standard measurement of relative masses. Define the term relative isotopic mass. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [2] [Total 4 marks]
5. The Group 7 element bromine was discovered by Balard in 1826. Bromine gets its name from the Greek bromos meaning stench. Bromine consists of a mixture of two isotopes, 79 Br and 81 Br. (i) What is meant by the term isotopes? ......................................................................................................................... ......................................................................................................................... [1]
(ii) Complete the table below to show the atomic structures of the bromine isotopes. protons neutrons electrons (^79) Br (^81) Br [2] (iii) Write the full electronic configuration of a bromine atom. 1s^2 ................................................................. [1] [Total 4 marks]
6. Calcium and its compounds, have properties typical of Group 2 in the Periodic Table. Calcium carbonate, CaCO 3 , reacts with acids such as nitric acid. A student neutralised 2.68 g of CaCO 3 with 2.50 mol dm–3^ nitric acid, HNO 3. The equation for this reaction is shown below. CaCO 3 (s) + 2HNO 3 (aq) → Ca(NO 3 ) 2 (aq) + CO 2 (g) + H 2 O(l) The student left the solution of calcium nitrate formed to crystallise. Crystals of hydrated calcium nitrate formed containing 30.50% of H 2 O, by mass. Calculate the formula of the hydrated calcium nitrate.
[Total 3 marks]
7. Rubidium, atomic number 37, was discovered in 1861 by Bunsen and Kirchoff.Rubidium is in Group 1 of the Periodic Table and the element has two natural isotopes, (^85) Rb and 87 Rb. (a) Explain the term isotopes. ......................................................................................................................... ......................................................................................................................... [1] (b) A sample of rubidium was analysed in a mass spectrometer to produce the mass spectrum below.
percentage
relative isotopic mass (i) Use this mass spectrum to help you complete the table below. isotope percentage number of protons neutrons electrons (^85) Rb (^87) Rb [3]
(ii) Calculate the relative atomic mass of this rubidium sample. Give youranswer to three significant figures.
A r = ................................ [2]
9. Antimony, Sb, is a metal used in alloys to make lead harder. Bullets contain about 1% of antimony for this reason. Antimony has two main isotopes. (i) What do you understand by the term isotopes? ......................................................................................................................... ......................................................................................................................... [1]
(ii) Complete the table below to show the properties of particles that make up isotopes. proton neutron electron relative mass relative charge [2] [Total 3 marks]
10. Relative atomic mass, A r, can be used to compare the masses of atoms of different elements. (i) Explain what you understand by the term relative atomic mass. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [3]
(ii) The antimony in a bullet was analysed by a forensic scientist to help solve a crime. The antimony was found to have the following percentage composition by mass: 121 Sb, 57.21%; 123 Sb, 42.79%. Calculate a value for the relative atomic mass of the antimony. Give your answer to 4 significant figures. A r ................................... [2] [Total 5 marks]
11. Carbon is in the p-block of the Periodic Table. Naturally occurring carbon contains a mixture of two isotopes, 12 C and 13 C. Complete the table below for the atomic structure of the isotopes 12 C and 13 C. isotope protons neutrons electrons (^12) C (^13) C [Total 2 marks] 12. A sample of carbon was found to contain 95% of 12 C and 5% of 13 C. (i) How could this information be obtained experimentally? ......................................................................................................................... [1]
(ii) The 13 C isotope has a relative isotopic mass of 13.00. Define the term relative isotopic mass. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [2]
(iii) Calculate the relative atomic mass of this sample of carbon to three significant figures. Ar = ............................................ [2] [Total 5 marks]
(ii) State two similarities between the atomic structures of 79 Br and 81 Br. ......................................................................................................................... ......................................................................................................................... [2] [Total 4 marks]
15. A fifty pence coin contains nickel alloyed with a metal A. Nickel exists as a mixture of three isotopes, nickel-58, nickel-60 and nickel-62. Complete the table below to show the atomic structures of the isotopes in metallic nickel. isotope protons neutrons electrons nickel- nickel- nickel- [Total 3 marks] 16. Metal A can be identified from its relative atomic mass. Analysis of a fifty pence coin showed that two isotopes of metalthe following percentage abundances. A were present with
isotope isotope 1 isotope 2 relative isotopic mass 63.0 65. % abundance 77.2 22. (i) What analytical method is used to obtain this information? ......................................................................................................................... [1]
(ii) Define the term relative atomic mass. ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [3]
(iii) Calculate the relative atomic mass of the sample of metal A. Give your answer to three significant figures. answer ........................... [2]
(iv) Use your answer to (iii) and the Data Sheet to suggest the identify of metal A. ......................................................................................................................... [1] [Total 7 marks]
