Electron configurationIB MYP Sciences: Subtopic test

1. 1
   A museum in Lagos is building a display of the first twenty elements. Each element card shows its electron configuration, written as the number of electrons in each shell from the inside outwards (for example, lithium is 2,1).

   (a)

   Which is the electron configuration of a phosphorus atom, which has 15 electrons?

   [1 mark]

   • A2,8,4
   • B2,5,8
   • C2,8,5
   • D2,8,6

   (b)

   One card shows an atom with the electron configuration 2,8,3. In which group and period is this element?

   [1 mark]

   • AGroup 3, period 2
   • BGroup 2, period 3
   • CGroup 8, period 3
   • DGroup 3, period 3

   (c)

   An element X has the electron configuration 2,8,6. State the group and the period of X, giving a reason for each.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A science teacher in Nairobi shows her class a neon sign and a sodium street lamp. She tells them that a neon atom has the electron configuration 2,8 and a sodium atom has the electron configuration 2,8,1.

   (a)

   What is the maximum number of electrons that the second electron shell can hold?

   [1 mark]

   • A2
   • B8
   • C6
   • D10

   (b)

   Which of these atoms has a stable, full outer shell?

   [1 mark]

   • AArgon, 2,8,8
   • BChlorine, 2,8,7
   • CPotassium, 2,8,8,1
   • DOxygen, 2,6

   (c)

   Explain, in terms of electron arrangement, why neon is unreactive but sodium is reactive.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student in Mumbai writes out electron configurations for ten elements and looks for patterns. Her results: lithium 2,1; beryllium 2,2; boron 2,3; carbon 2,4; nitrogen 2,5; oxygen 2,6; fluorine 2,7; neon 2,8; sodium 2,8,1; magnesium 2,8,2. She proposes the hypothesis: "The number of electrons in the outer shell of an atom is equal to the period number of its element."

   (a)

   Describe the pattern in the student's data from lithium to neon, and what happens at sodium.

   [3 marks]

   (b)

   Evaluate the student's hypothesis using the data in her results.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A company in Dubai plans a tethered observation balloon that will lift twenty visitors above the city. The engineers are choosing between hydrogen, whose atoms have one electron, and helium, whose atoms have two electrons, to fill the balloon. Neon (electron configuration 2,8) was also suggested but was ruled out on cost.

   (a)

   Explain, in terms of electron configuration, why helium is unreactive, why hydrogen is reactive, and how the configurations of helium and neon show where each is in the periodic table.

   [6 marks]

   (b)

   Discuss and evaluate the use of helium rather than hydrogen to fill the balloon.

   [6 marks]

   Total for question 4: 12 marks

End of questions