This question is about copper and about the arrangement of elements in the Periodic Table. Table 18.1 gives information about the two isotopes of copper. Is...
Question 1 Report
This question is about copper and about the arrangement of elements in the Periodic Table.
Table 18.1 gives information about the two isotopes of copper.
| Isotope of copper | Nucleon number | Number of protons | Number of neutrons | Abundance / % |
|---|---|---|---|---|
| copper-63 | 63 | 29 | … | 70 |
| copper-65 | 65 | 29 | … | 30 |
(a) Complete the shaded 'Number of neutrons' column of Table 18.1. [2]
(b) Explain, in terms of subatomic particles, why the two isotopes are both atoms of copper yet have different masses. [2]
(c) Calculate the relative atomic mass of copper from the abundance data. Show all your working. [3]
(d) Copper is a transition element. State two properties of copper, other than its density, that are typical of a transition metal but not of a Group I metal. [2]
(e) Fig. 18.1 shows the electron arrangement of a different element, Z, in the same period as copper.
(i) Deduce the proton number, group and period of element Z. [3]
(ii) Element Z reacts vigorously with cold water. Write a balanced symbol equation for the reaction, giving the hydroxide of Z (formula ZOH) and a gas. [2]
(iii) Explain why element Z is more reactive than the element directly above it in the same group. [2]
(f) Copper forms ions Cu+ and Cu2+. State the term for this behaviour and give the formulae of the two oxides these ions form with O2−. [3]
(g) State, giving a reason, whether copper or element Z is the better conductor of heat, or whether they would be similar. [1]
(h) Both copper and element Z are metals. State one feature of their structure that they share. [1]
Answer Details
(a) Neutrons = nucleon number \(-\) protons. Copper-63: \(63 - 29 = 34\) neutrons [1]; copper-65: \(65 - 29 = 36\) neutrons [1].
(b) Both isotopes have the same number of protons, 29, so both are copper [1]; they differ in neutrons (34 and 36), giving different nucleon numbers and therefore different masses [1]. Chemical identity is fixed by proton number, not by mass.
(c) Relative atomic mass is the weighted mean [method 1]:
\[ A_r = \frac{(63\times 70) + (65\times 30)}{100} = \frac{4410 + 1950}{100} = \frac{6360}{100} \quad [1] \] \[ = 63.6 \quad [1] \](d) Any two transition-metal properties, other than density: forms coloured compounds; shows variable valency (\(\text{Cu}^{+}\) and \(\text{Cu}^{2+}\)); acts as a catalyst; has a high melting point [2]. A Group I metal shows none of these (white compounds, a single 1+ charge, low melting point).
(e) Element Z has \(2 + 8 + 8 + 1 = 19\) electrons.
(i) Proton number 19 [1]; Group I [1] (1 outer electron); Period 4 [1] (4 occupied shells).
(ii) A Group I metal reacts with cold water to give its hydroxide and hydrogen gas [products 1; balanced 1]:
\[ 2\text{Z} + 2\text{H}_2\text{O} \rightarrow 2\text{ZOH} + \text{H}_2 \](iii) Z is more reactive than the element directly above it because it has one more electron shell, so its outer electron is further from the nucleus and more shielded [1]; the weaker nuclear pull means that outer electron is lost more easily, and losing that electron is how a Group I metal reacts [1].
(f) Forming both \(\text{Cu}^{+}\) and \(\text{Cu}^{2+}\) is variable valency (variable oxidation state) [1]. With the oxide ion \(\text{O}^{2-}\) the charges balance to give \(\text{Cu}_2\text{O}\) [1] (two 1+ ions per oxide) and \(\text{CuO}\) [1] (one 2+ ion per oxide).
(g) They would be similar; both are good conductors of heat [1], because both are metals with delocalised electrons free to move and transfer thermal energy.
(h) They share a giant metallic lattice of positive ions in a sea of delocalised electrons [1].
Download The App On Google Playstore
Everything you need to excel in your exams
