Fig. 1 shows a simplified mass spectrum produced from an atmospheric argon sample in a school science department. The height of each line gives the relative...
Question 1 Report
Fig. 1 shows a simplified mass spectrum produced from an atmospheric argon sample in a school science department. The height of each line gives the relative abundance of ions detected. All ions have the same charge.
Table 1 gives more precise abundance data for the same gas.
| Argon isotope | Relative abundance / % |
|---|---|
| 36 | 0.34 |
| 38 | 0.06 |
| 40 | 99.60 |
(a) State which isotope gives the tallest line in Fig. 1. [1]
(b) Give the number of protons in an argon atom. [1]
(c) Calculate the number of neutrons in argon-38. [1]
(d) Complete the electronic configuration of an argon atom: 2, 8, ________. [1]
(e) Calculate the relative atomic mass of argon using Table 1. [3]
(f) Explain why argon-36 and argon-40 are both atoms of argon. [2]
(g) State the relative charge of a neutron. [1]
(h) Give one property of protons and neutrons that makes up almost all of an atom's mass. [1]
(i) When argon is in a tube at room temperature, state its physical state. [1]
(j) Name the gas produced when magnesium reacts with dilute acid, rather than argon. [1]
Answer Details
(a) Argon-40 gives the tallest line because it has the greatest relative abundance. [1]
(b) An argon atom has 18 protons. [1]
(c) \[38-18=20\] Argon-38 has 20 neutrons. [1]
(d) The electronic configuration is \(2,8,\boldsymbol{8}\). [1]
(e) \[\frac{(36\times0.34)+(38\times0.06)+(40\times99.60)}{100}=39.9752\] The relative atomic mass is 39.98. [3]
(f) Argon-36 and argon-40 both have 18 protons. Atomic number, the number of protons, determines which element an atom is, so both are argon. [2]
(g) A neutron has relative charge 0. [1]
(h) Each proton and neutron has relative mass approximately 1, so together they account for almost all atomic mass. [1]
(i) At room temperature, argon is a gas. [1]
(j) Magnesium reacting with dilute acid produces hydrogen. [1]
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