Chapter 8

• How many outer shell electrons do group 2 elements have?

  Two outer shell electrons
• How does reactivity change in group 2 elements?

  Reactivity increases down the group
• What causes the increase in reactivity down group 2?

  Decreased attraction between nucleus and outer electrons
• What happens to atomic radius down group 2?

  Atomic radius increases
• What effect does shielding have on group 2 reactivity?

  Shielding increases down the group
• What do group 2 oxides release when they react with water?

  OH- ions
• What type of solutions do group 2 oxides form in water?

  Alkaline solutions of metal hydroxide
• How soluble are group 2 hydroxides in water?

  Only slightly soluble
• What happens when the solution of group 2 hydroxides becomes saturated?

  A solid precipitate forms
• How does solubility of hydroxides change down group 2?

  Solubility increases down the group

  
• What is the pH of Mg(OH)2 in water?

  10
• What is the pH of Ba(OH)2 in water?

  13
• What is the method for experimenting with group 2 oxides and water?

  1. Add a spatula of oxide to water
  2. Use less water than needed to dissolve
  3. Observe a saturated solution with undissolved solid
  4. Measure the pH of the solution
  5. Note that alkalinity increases down the group
• How does calcium hydroxide affect acidic soils?

  It increases the pH of the soil
• What is the main use of group 2 compounds in medicine?

  As antacids for treating indigestion
• What are the main ingredients in most indigestion tablets?

  Magnesium and calcium carbonate
• What is milk of magnesia?

  A suspension of magnesium hydroxide in water
• What is the main acid in the stomach?

  Hydrochloric acid
• What are the key points from the summary questions about group 2 reactions?

  • Group 2 metals add electrons to other species
  • Magnesium is oxidized from 0 to +2
  • Hydrogen is reduced from +1 to 0
  • Reactivity increases down the group due to decreased attraction
  • Solubility of hydroxides increases down the group
• What is the relationship between hydroxide ion concentration and pH in group 2 compounds?

  Higher hydroxide concentration increases pH
• What group are the most reactive non-metals?

  Group 17
• How do halogens occur on Earth?

  As stable halide ions in seawater
• What are the trends in boiling points of halogens?

  • All halogens exist as diatomic molecules
  • Halogens exist in all states
  • In solid states, they form lattices with simple molecular structures
  • More electrons lead to stronger London forces
  • Increased energy is needed to break intermolecular forces
  • Boiling points increase with more electrons
• What happens to each halogen atom in redox reactions?

  Each halogen gains one electron to form a 1- halide ion
• What is the electron configuration of a halide ion?

  Configuration of the nearest noble gas
• Why is a halogen called an oxidizing agent?

  It oxidizes other species by gaining electrons
• What are the characteristics of halogen displacement reactions?

  • All halogens exist as diatomic molecules
  • Halogens are oxidizing agents
  • Halogen atoms are reduced as they gain one electron
• What is the appearance of fluorine gas?


  Pale yellow gas
• What is the appearance of chlorine gas?


  Pale green gas
• What is the appearance of bromine?

  Red-brown liquid
• What is the appearance of iodine?

  Shiny grey-black solid
• What are the reactivity patterns of halogens in displacement reactions?

  • Chlorine can react with Br- and I-
  • Bromine can react with I- only
  • Iodine does not react at all

  
• What trends occur as you go up Group 17?

  • Atomic radius decreases
  • Shielding decreases
  • More nuclear attraction is needed
  • Reactivity increases
• What is disproportionation in chemistry?

  When a species is simultaneously oxidized and reduced
• What are the effects of halogens on health and the environment?

  • Kills bacteria
  • Stops disease
  • Damages the skin
  • Toxic
• What happens to blue litmus paper when exposed to halogens?

  Turns red then white
• What does qualitative analysis rely on?

  Simple observations rather than measurements
• How can qualitative analysis be performed?

  Quickly on a test-tube scale
• What is the procedure for the carbonate test?

  • Add dilute nitric acid to the sample
  • Look for bubbles indicating carbon dioxide
  • Bubble gas through lime water to confirm
  • Cloudiness indicates presence of carbon dioxide
• What does bubbling gas through lime water prove?

  It confirms the gas is carbon dioxide