Compounds formed by the union of two different halogens are called.......

Explanation

### Step-by-Step Text Solution:

1. **Understanding the Question**: The question asks for the term used to describe compounds formed by the union of two different halogens. Halogens are a group of elements in Group 17 of the periodic table, which includes fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

2. **Identifying the Compounds**: When two different halogens combine, they form compounds known as interhalogen compounds. This term specifically refers to compounds that consist of two different halogen atoms bonded together.

3. **Defining Interhalogen Compounds**: Interhalogen compounds can be represented as XY, where X and Y are different halogen elements. Examples of interhalogen compounds include:
- IF7 (iodine heptafluoride)
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