Question

A scientist is combining two grey elements he thinks he will get a compound why is this prediction wrong

Answer 1

In a compund, the proportion must be fixed, unlike mixture. Therefore, if he just combine two elements, there must be excess elements mixed in it.
Second, how did he combined two elements? In order to create a compund, either heat or electricity must be applied.
Therefore, even if he used heat / electricity, he still hasn't got the right proportion, therefore he must have mixed some excess elements into the compund that he thought he made.

Answer 2

Answer: The combination of two grey elements will lead to the formation of molecule of element.

Explanation:

Element is defined as the substance having similar kind of atoms.

Compound is defined as the substance having different kind of atoms.

Molecules of elements are defined as the substances which are made up of similar type of atoms. For Example: $F_2$ etc..

Molecules of compounds are defined as the substances which are made up of different type of atoms. For Example: $CO_2$ etc..

We are given:

Two grey elements are combining to form a molecule. The molecule formed is known as molecule of element because 2 same kind of elements are combining.

Hence, this will lead to the formation of molecule of element.