Occurrence Of Metals

Step 1: Understand the alloys of iron.
Invar is an alloy of iron and nickel, known for its low coefficient of thermal expansion.
It is used in precision instruments.
Step 2: Identify the correct alloy.
Brass is an alloy of copper and zinc, vitallium is a cobalt-based alloy, and solder is an alloy of lead and tin, none of which are alloys of iron.

Step 1: Alkali Metals' Properties
Alkali metals (Group 1 elements) are known for their strong electropositive character, meaning they readily lose electrons to form positive ions (cations).
Step 2: Explanation of Other Options
Option (a) Neutral is incorrect because alkali metals are not neutral; they are highly electropositive.

Option (c) Electronegative is incorrect because alkali metals have low electronegativity, which means they are not likely to attract electrons.
Option (d) Non-metallic is incorrect because alkali metals are metals, not non-metals.
Step 3: Conclusion
Thus, alkali metals are strongly electropositive.