Elements of Group 16, 17 and 18 — MHT-CET Chemistry

Formulas (3)

• The Chalcogen Family and Its Trends · Down group 16
  $$\text{size}\uparrow,\ \text{density}\uparrow,\ \text{IE}\downarrow,\ \text{reactivity}\downarrow:\quad \text{S} > \text{Se} > \text{Te} > \text{Po}\ (\text{IE})$$
• Hydrides H₂E and Oxygen Against Sulphur · Group 16 hydrides
  $$\text{stability: } \text{H}_2\text{O} > \text{H}_2\text{S} > \text{H}_2\text{Se} > \text{H}_2\text{Te};\quad \text{acidity: reverse}$$
• Dioxygen and Ozone · Formation of ozone
  $$3\text{O}_2 \rightarrow 2\text{O}_3;\quad \Delta H > 0,\ \Delta S < 0$$

Reference tables (1)

Watch out for (4)

• Putting astatine in group 16
  → The Chalcogen Family and Its Trends
• Expecting stability and acidity to run the same way
  → Hydrides H₂E and Oxygen Against Sulphur
• Calling ozone paramagnetic like oxygen
  → Dioxygen and Ozone
• Taking the S–S–S angle as 104.5° or 120°
  → Sulphur: Allotropes, SO₂, Oleum and Ores

Formulas (2)

• Halogen Properties and the Hydrogen Halides · Chlorine with hot concentrated NaOH
  $$3\text{Cl}_2 + 6\text{NaOH} \xrightarrow{\text{hot, conc.}} 5\text{NaCl} + \text{NaClO}_3 + 3\text{H}_2\text{O}$$
• Interhalogen Compounds · Interhalogen stoichiometry
  $$\text{XX}'_n,\ n \in \{1, 3, 5, 7\};\quad \text{ClF} > \text{ICl} > \text{IBr} > \text{BrCl}\ \text{(thermal stability)}$$

Reference tables (1)

Watch out for (3)

• Putting HI above HF in boiling point
  → Halogen Properties and the Hydrogen Halides
• Reading 'halous' as the lowest acid
  → Oxoacids of the Halogens
• Assuming the iodine interhalogens are all solids
  → Interhalogen Compounds

Formulas (1)

• Noble Gas Uses and Xenon Compound Shapes · Lone pairs on xenon
  $$\text{lp} = \frac{8 - n(\text{Xe-F}) - 2\,n(\text{Xe=O})}{2}$$

Watch out for (1)

• Counting an Xe=O bond as one electron
  → Noble Gas Uses and Xenon Compound Shapes