Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Atomic Structure
108 practice questions
Topics covered
Practice questions
41–44 of 44 · Easy
Question 41
5 marks · Easy
Answer and see the solution →A sample of an element X consists of two isotopes. 30% of the atoms are isotope X-24 (with mass number 24) and 70% are isotope X-25 (with mass number 25). The atomic number of element X is 12.
(a)[3 marks]Calculate the relative atomic mass of element X from its isotopic abundances.
(b)[2 marks]How many electrons are there in an atom of X? State your answer and explain your reasoning.
Question 42
5 marks · Easy
Answer and see the solution →Two atoms of lithium are shown below.
Isotopes of lithium Isotope Mass number Atomic number Number of neutrons 6 3 7 3 (a)[2 marks]Complete the table by calculating the number of neutrons in each isotope.
(b)[2 marks]Describe one way in which the isotopes of lithium are the same, and one way in which they are different.
(c)[1 mark]State the number of electrons in a neutral atom of .
Question 43
5 marks · Easy
Answer and see the solution →An element X has two naturally occurring isotopes: X-64 and X-66. In a sample of X, 75% of the atoms are X-64 and 25% are X-66. The atomic number of X is 30.
(a)[3 marks]Calculate the relative atomic mass of element X. Show all your working.
(b)[1 mark]How many electrons are present in one atom of X?
(c)[1 mark]State the number of electrons in an ion of X with a 2+ charge.
Question 44
5 marks · Easy
Answer and see the solution →Use your knowledge of isotopes and atomic structure to answer the following questions about phosphorus.
(a)[2 marks]Describe two ways in which two isotopes of phosphorus are the same.
(b)[1 mark]Describe one way in which two isotopes of phosphorus are different.
(c)[1 mark]The atomic number of phosphorus is 15. State the number of electrons in a neutral atom of phosphorus.
(d)[1 mark]State the number of electrons in a phosphorus ion with a 3– charge.