If I am correct the answer would be iron and nickel.
Answer:

Explanation:
A mole is any quantity of a substance that contains 6.02 × 10²³ particles. At standard temperature and pressure, or STP, 1 mole of as is equal to 22.4 liters. This is true for any gas, regardless of the specific kind.
Although it is not specified, we can assume this gas is at STP. Let's set up a ratio using this information: 22.4 L/mol

Multiply by the given number of liters: 12

Flip the ratio so the liters of chlorine cancel.




The original measurement of liters has 2 significant figures, so our answer must have the same.
For the number we found, that is the hundredth place.
The 5 in the thousandth place tells us to round the 3 up to a 4.

12 liters of chlorine gas at STP is approximately <u>0.54 moles of chlorine gas.</u>
When the neutrons and electrons are the same. For example, sodium (Na) has an atomic mass of 11, meaning it has 11 protons and 11 electrons etc.
<h3>Further explanation</h3>
Given
Reaction
H₂ (g) + I₂ (g) → 2HI(g)
Required
The equilibrium constant
Solution
The equilibrium constant is the value of the product in the equilibrium state of the substance in the right (product) divided by the substance in the left (reactant) with the exponents of each reaction coefficient
The equilibrium constant for reaction
pA + qB ⇒ mC + nD
![\large {\boxed {\bold {K ~ = ~ \frac {[C] ^ m [D] ^ n} {[A] ^ p [B] ^ q}}}}](https://tex.z-dn.net/?f=%5Clarge%20%7B%5Cboxed%20%7B%5Cbold%20%7BK%20~%20%3D%20~%20%5Cfrac%20%7B%5BC%5D%20%5E%20m%20%5BD%5D%20%5E%20n%7D%20%7B%5BA%5D%20%5E%20p%20%5BB%5D%20%5E%20q%7D%7D%7D%7D)
So for the above reaction :
![\tt K=\dfrac{[HI]^2}{[H_2][I_2]}](https://tex.z-dn.net/?f=%5Ctt%20K%3D%5Cdfrac%7B%5BHI%5D%5E2%7D%7B%5BH_2%5D%5BI_2%5D%7D)