At 1 atm will the `Delta_(f)H^(@)` be zero for `CI_(2)(g)` and `Br_(2)(g)`? Explain.

Explanation

To determine whether the standard enthalpy of formation (ΔfH°) for Cl2(g) and Br2(g) at 1 atm is zero, we can follow these steps:

### Step 1: Understand the Definition of Standard Enthalpy of Formation
The standard enthalpy of formation (ΔfH°) of a substance is defined as the change in enthalpy when one mole of the substance is formed from its elements in their standard states at 1 atm pressure and a specified temperature (usually 298.15 K).

### Step 2: Identify the Standard State of Elements
The standard state of an element is its most stable physical form at 1 atm and 298.15 K. For example:
- Cl2(g) is the gaseous form of chlorine at standard conditions.
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