<span>In order for an ionic compound to be created, there has to be a reaction between a metal and a non-metal. Having this in mind, the correct answer is A. strontium and chlorine. Strontium (Sr) is an alkaline earth metal, whereas chlorine (Cl) is a halogen gas, so a non-metal. There is no this type of a combination of metal + non-metal in other options, so only A is correct.</span>
It is more likely to be found as a COMPOUND, as it is more reactive, by the time we found them, they're already reacted with other elements or compounds to form new compounds.
Example is oxygen, it is very reactive, therefore we often found oxygen in water, which is H2O, in earth, instead of just pure oxygen.
Answer:

Explanation:
Hello,
In this case, the undergoing chemical reaction is:

Thus, in terms of pressures, the rate becomes:

Thus, the rate of change for the partial pressure of ammonia turns out:
![r_{NH_3}=2*(-r_{N_2H_4})\\r_{NH_3}=2*[-(-70torr/h)]\\r_{NH_3}=140torr/h](https://tex.z-dn.net/?f=r_%7BNH_3%7D%3D2%2A%28-r_%7BN_2H_4%7D%29%5C%5Cr_%7BNH_3%7D%3D2%2A%5B-%28-70torr%2Fh%29%5D%5C%5Cr_%7BNH_3%7D%3D140torr%2Fh)
The rate of decrease of partial pressure of urea is taken negative as it is a reactant whereas ammonia a product which has 2 as its stoichiometric coefficient.
Best regards.
Answer:
Number of delocalized electrons
Explanation:
Magnesium has more delocalized electrons compared to sodium and this accounts for the higher melting point.
- When magnesium atoms comes together to form a metallic bonds, they have more network of delocalized electrons.
- There is more pull for the localized electrons due to the nuclear charge on the nucleus.
- This strong intermolecular metallic bond increases the melting point of magnesium.