Electron arrangementIB MYP Chemistry: Subtopic test

1. 1
   A teacher tells her class that a neutral sulfur atom has 16 electrons. She asks the students to work out how those electrons are arranged in shells, and what the arrangement shows about where sulfur sits in the periodic table.

   (a)

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

   [1 mark]

   • A8
   • B2
   • C18
   • D10

   (b)

   Which is the electron arrangement of a sulfur atom?

   [1 mark]

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

   (c)

   Explain how the electron arrangement of sulfur shows its group and period in the periodic table.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A chemist compares three elements with different reactivity. Argon has atomic number 18 and is very unreactive. Sodium has atomic number 11 and potassium has atomic number 19, and both are very reactive metals that must be stored under oil.

   (a)

   What is the electron arrangement of potassium?

   [1 mark]

   • A2,8,9
   • B2,8,8,1
   • C2,8,1
   • D2,8,7,2

   (b)

   How many electrons are in the outer shell of an argon atom?

   [1 mark]

   • A2
   • B1
   • C18
   • D8

   (c)

   Explain why sodium and potassium have similar chemical properties.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Calcium has atomic number 20 and is a metal in the same group of the periodic table as magnesium, which has atomic number 12. A student is using electron arrangements to compare the two metals.

   (a)

   State the electron arrangement of calcium and use it to give the group and period of calcium.

   [3 marks]

   (b)

   Magnesium has the electron arrangement 2,8,2. Compare the electron arrangements of magnesium and calcium, and explain what this shows about their positions in the periodic table.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A school science club is making a display of the first 20 elements. They record the number of outer-shell electrons in each atom. Lithium to neon (atomic numbers 3 to 10) have 1, 2, 3, 4, 5, 6, 7 and 8 outer electrons in turn. Sodium to argon (atomic numbers 11 to 18) show the same pattern, from 1 to 8. Potassium has 1 outer electron and calcium has 2. The club also wants to explain to younger students why some elements are handled very differently from others in everyday life.

   (a)

   Describe the pattern in the club's data and use it to explain how electron arrangement decides the group and period of an element. Use the pattern to predict the group and period of phosphorus, which has atomic number 15.

   [6 marks]

   (b)

   Argon, with electron arrangement 2,8,8, is used in welding and in light bulbs, but potassium, with electron arrangement 2,8,8,1, must be stored under oil and handled with great care. Discuss and evaluate how knowing the electron arrangement of an element helps people to use elements safely.

   [6 marks]

   Total for question 4: 12 marks

End of questions