Answer: Image 3 is a compound.
Explanation: A compound is something that consists of two or more different elements bonded chemically.
A molecule is formed when two or more elements combine chemically.
An element is described as something which cannot be broken down by any chemical means.
We are given 4 images.
Image 1 is an element as it is showing the shell structure of Oxygen (O) element.
Image 2 is an element as only 1 element is known that is Magnesium (Mg).
Image 3 is a compound as in the structure 2 elements are shown which is bonded together. Elements present in this are Carbon (C) and Oxygen (O).
Image 4 is a molecule as in the structure 2 H-atoms combine chemically, but it cannot be considered as compound as the two elements are not different.
