1.6 periodic table

• What is the basic structure of the periodic table?

  It organizes elements by atomic number.
• Why do chemists use salt?

  It helps in various chemical reactions.
• What does Ca²⁺ represent?

  Calcium ion with a +2 charge.
• Why do ionisation energies increase across a period?

  Due to increased nuclear charge and attraction.
• Why do ionisation energies decrease down a group?

  Due to increased distance from the nucleus.
• What is a reducing agent?

  A species that donates electrons.
• What is an oxidising agent?

  A species that accepts electrons.
• What is a redox reaction?

  It involves electron transfer between species.
• What does the mnemonic OIL RIG stand for?

  Oxidation Is Losing, Reduction Is Gaining.
• What are the oxidation numbers for Na and Cl in Na → Na⁺ + Cl⁻?

  Na: 0, Cl: -1
• What is the oxidation state of the chloride ion?

  • 1
• Assign oxidation numbers to Na₂SO₄.

  Na: +1, S: +6, O: -2
• Assign oxidation numbers to NF₃.

  1. +3, F: -1
• What is the oxidation number of oxygen in compounds?

  • 2 or -1
• What happens to oxidation numbers in a redox reaction?

  They must add up to zero or the ion's charge.
• What is the oxidation number of Mn in MnO₄⁻?

  +7
• What is the trend in properties of s-block elements?

  They show increasing reactivity down the group.
• What is the color of the element Ba?

  Yellow
• Why does chlorine displace bromide from bromides?

  Due to decrease in oxidising power down the group.
• What is an electronegative element?

  One with a strong affinity for electrons.
• How does solubility of Group 2 compounds change down the group?

  Increases for some, decreases for others.
• Write a balanced equation for chlorine acting on KI.

  Cl₂ + 2KI → 2KCl + I₂
• What happens to the melting temperatures of halogens down the group?

  They increase from fluorine to iodine.
• How does volatility change down the group of halogens?

  Volatility decreases from fluorine to iodine.
• What is the general reaction of halogens with metals?

  They form halides with decreasing reactivity.
• What is the significance of the reaction of halide ions with silver ions?

  It is important for qualitative analysis.
• What color precipitate does silver chloride form?

  White
• What color precipitate does silver bromide form?

  Pale cream
• What color precipitate does silver iodide form?

  Pale yellow
• Why is fluoride added to toothpaste?

  To prevent tooth decay and strengthen bones.
• What is the equilibrium reaction of chlorine in water?

  Cl₂ + H₂O ⇌ HOCl + HCl
• What ethical issues are raised by adding chlorine to water supplies?

  Concerns about health effects at high concentrations.
• What are the benefits of chlorine in water treatment?

  Kills harmful bacteria like typhoid and cholera.