How many different 2-person conversations would happen at a party of 30 people

Is this a single replacement reaction or there is no

Me i dont know what to do! the table compares the number of electrons in two unknown neutral atoms. comparison of electrons atom number of electrons a 10 d 11 use this information to determine the number of valence electrons in the atoms. which of the following correctly compares the stability of the two atoms? both are unreactive. both are highly reactive. a is unreactive and d is reactive. a is reactive and d is unreactive.

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation: