Solar spectroscopy (history of discovery): Which element was first discovered in the Sun’s chromosphere before being found on Earth? Identify the element detected during the 1868 total solar eclipse via a new spectral line. Choose the correct element.

What is being asked?
Which element was first identified in the Sun's chromosphere (not on Earth) through spectroscopy.

Given data

• Context: Solar chromosphere, 19th-century spectroscopy
• Clue: Discovered during the 1868 eclipse via an unknown yellow spectral line (D₃)

Concept/Approach
A previously unknown line observed by Janssen and Lockyer was attributed to a new element, later named helium (from Helios, Sun). Helium was isolated on Earth only later.

Step-by-step reasoning
1) Spectral line D₃ in the yellow region did not match known elements.2) The element producing it was named helium.3) Therefore, the first element discovered in the Sun's chromosphere was helium.

Common pitfalls
Choosing hydrogen or neon; both were already known on Earth and are not the chromosphere-first discovery.

Final Answer
Helium