Alkali Metals

Why do alkali metals have the largest atomic radii in their periods?

Because they have only one valence electron and a low effective nuclear charge, resulting in less attraction to the nucleus.

Which group in the periodic table is most easily ionized and why?

Group 1 (alkali metals); they have low ionization energies due to their large atomic size and weak nuclear attraction to the outer electron.

What type of ions do alkali metals form and why?

They form M⁺ ions easily due to their low ionization energy and single valence electron.

What distinguishes lithium’s bonding from other alkali metals?

Lithium can form covalent bonds due to its small size and high charge density; other alkali metals mostly form ionic and metallic bonds.

What happens to the melting point, heat of sublimation, and hydration energy down Group 1?

All decrease due to increasing atomic size and weaker interatomic forces.

How are lithium and sodium typically prepared?

By electrolysis of their molten salts (e.g., NaCl):
NaCl(l) + e⁻ → Na(l) + Cl⁻

How are potassium, rubidium, and cesium prepared?

By metal displacement:
MCl(l) + Na(g) → NaCl(l) + M(g)
(M = K, Rb, or Cs)

How do alkali metals react with water?

General reaction:
2M(s) + 2H₂O(l) → 2M⁺(aq) + 2OH⁻(aq) + H₂(g)

Describe the trend in reactivity with water among alkali metals.

• Li: reacts slowly

• Na: reacts vigorously

• K: reacts even more vigorously

• Rb, Cs: react explosively

Which alkali metal reacts uniquely with nitrogen? What does it form?

Lithium, forming lithium nitride (Li₃N):
6Li + N₂ → 2Li₃N

Why does lithium hydroxide decompose to lithium oxide instead of subliming like other group members?

Due to lithium’s small size, better ion packing, and higher lattice energy.

How do lithium salts behave in terms of solubility?

• Lithium salts with strong acid anions: more soluble

• With weak acid anions: less soluble

• Some lithium halide salts: soluble in organic solvents

What are some key applications of lithium?

• Used in disposable and rechargeable batteries

• Mood stabilizer in medicine

• Lubricants (e.g., lithium stearate)

• Lowest density metal

• Easily oxidized

What are major uses of sodium?

• NaOH in drain cleaners

• NaCl as table salt

• Sodium vapor lamps

• Strong reducing agent

What is potassium mainly used for?

• Fertilizers

  • Na⁺/K⁺ ion exchange crucial in nerve transmission

What are some uses of rubidium (Rb)?

• Gives purple color in fireworks

  • Used in Rb atomic clocks (high accuracy)

What are some uses of cesium (Cs)?

• Cs atomic clocks (ultra-precise)

• Oil drilling: Cs salts float debris

  • Removes O₂ from sealed tubes (reactive Cs layers)

Why does francium have no practical uses?

Extremely reactive and radioactive; short half-life