Question

combinations of two or more different elements held together in fixed proportions are known as ______. ions nuclei compounds isotopes atoms

Explanation:

To solve this, we analyze each option:

• Ions: Charged particles (atoms or groups), not combinations of elements in fixed proportions.
• Nuclei: Central part of an atom, contains protons/neutrons, not element combinations.
• Compounds: Defined as substances with two or more different elements in fixed proportions (e.g., \(H_2O\) has 2 H and 1 O).
• Isotopes: Atoms of the same element with different neutrons, not different elements.
• Atoms: Basic units of elements, not combinations of different elements.

So the correct term is compounds.

Answer:

C. compounds