Answer: Marie and Pierre Curie.
- A Marie and Pierre Curie
- B Humphry Davy in most textbook accounts
- C Mendeleev during normal conditions
- D Moseley as generally observed
Correct answer: A. Marie and Pierre Curie
Explanation: Marie and Pierre Curie discovered radium (and polonium) in 1898 from pitchblende ore.
Each s-block metal ion emits a characteristic flame colour because heating excites electrons to higher energy levels; light is emitted as they fall back, with the colour determined by the specific energy gap.
Concept context
Group 1 (alkali metals) and Group 2 (alkaline earth metals). Learn their reactions with water and air, important compounds like NaOH, Na₂CO₃, and CaCO₃, and anomalous behaviour of lithium and beryllium.