Group 1: Alkali Metals

Group 1 elements, known as the alkali metals, include Li, Na, K, Rb, Cs, and Fr. They possess the outer electronic configuration ns¹. Consequently, they are highly reactive, particularly with water, and they easily form +1 cations. In addition, alkali metals are soft, have relatively low melting points, and act as strong reducing agents.

Electronic Configuration & General Properties of Alkali Metals

All alkali metals share the valence configuration ns¹ (where n = period number). This single valence electron explains their distinctive features: low ionization energy, strong metallic character, and high reactivity. Moreover, their tendency to form stable M⁺ ions increases as we move down the group.

Quick Reference Table of Alkali Metals

Element	Symbol	Atomic No.	Valence Config	Typical Reaction / Use
Lithium	Li	3	2s¹	Li-ion batteries, lightweight alloys
Sodium	Na	11	3s¹	Salt production, street lamps, chemical syntheses
Potassium	K	19	4s¹	Fertilizers, biological roles (K⁺)
Rubidium	Rb	37	5s¹	Research, photoelectric cells
Cesium	Cs	55	6s¹	Atomic clocks, specialty electronics
Francium	Fr	87	7s¹	Extremely radioactive; studied only in research

Chemical Behaviour & Reactions of Alkali Metals

• With water: They react vigorously → M + H₂O → MOH + ½H₂ (e.g., 2Na + 2H₂O → 2NaOH + H₂).
• With oxygen: They form oxides, peroxides, or superoxides depending on the element and conditions.
• With halogens: They combine directly to give ionic halides (e.g., NaCl).
• Reducing agents: Because they donate their outer electron easily, alkali metals act as powerful reducing agents.

Periodic Trends in Alkali Metals

• Reactivity steadily increases down the group (Li < Na < K < Rb < Cs < Fr).
• Atomic and ionic radii expand, while ionization energy decreases.
• Melting and boiling points generally fall; meanwhile, densities usually rise with some anomalies.

Applications of Alkali Metals

• Lithium: Rechargeable batteries, lightweight alloys.
• Sodium: Industrial chemicals, Na vapor lamps for street lighting.
• Potassium: Essential fertilizers, biological electrolytes.
• Rubidium & Cesium: Atomic clocks, advanced research, photoelectric cells.

Safety & Handling of Alkali Metals

Alkali metals react violently with water; therefore, they must be stored under mineral oil or in an inert atmosphere. Always use non-sparking tools, wear proper PPE, and follow strict safety protocols. Scientists only study francium in trace amounts because it is highly radioactive.

MCQs: Test Your Understanding of Alkali Metals

1. What is the general electronic configuration of alkali metals?
   Answer: ns¹
2. Which alkali metal shows the highest reactivity?
   Answer: Cesium (Cs), while francium is predicted to be more reactive but remains rare and radioactive.
3. What are the products when sodium reacts with water?
   Answer: Sodium hydroxide (NaOH) and hydrogen gas (H₂).
4. Why should alkali metals be stored under oil?
   Answer: Because oil prevents contact with air or moisture, which would otherwise trigger violent reactions.

FAQs on Alkali Metals

Q: Why does reactivity increase down Group 1?
A: The outer electron lies farther from the nucleus and experiences stronger shielding, so it is removed more easily.

Q: Can alkali metals exist freely in nature?
A: No. Because they are highly reactive, alkali metals only occur as stable compounds (salts) in nature.

Q: Which alkali metal is mainly used in batteries?
A: Lithium is widely used in modern rechargeable batteries (Li-ion cells).

Britannica — Alkali Metals