Periodic trendsIB MYP Chemistry: Flashcards

Exam questions on Periodic trends

1. A student collects data on the atoms of the period 3 elements. Their approximate atomic radii, in picometres (pm), are: sodium 186, magnesium 160, aluminium 143, silicon 118, phosphorus 110, sulfur 103 and chlorine 99.
   Describe how metallic character changes across period 3 from sodium to chlorine.2 marks
2. The elements in Group 4 of the periodic table are carbon, silicon, germanium, tin and lead. Carbon is a brittle non-metal, silicon and germanium are semiconductors, and tin and lead are shiny, malleable metals that conduct electricity well.
   Explain why the atomic radius increases down Group 4.2 marks
3. A student investigates the reactivity of three halogens (Group 7) using displacement reactions. She adds a few drops of each halogen solution to separate solutions of potassium chloride, potassium bromide and potassium iodide, and records a reaction when the mixture changes colour. Chlorine solution changed potassium bromide solution orange and potassium iodide solution brown, but did not change potassium chloride solution. Bromine solution changed potassium iodide solution brown, but did not change potassium chloride or potassium bromide solution. Iodine solution caused no change with any of the three.
   Identify the independent variable, the dependent variable and one control variable in this investigation.3 marks