1. which of the following is a single replacement reaction? cao + h2o yields ca(oh)2 mg + 2hno3 yields mg(no3)2 + h2 naoh + hcl yields h2o + nacl ch4 + 2o2 yields co2 + 2h2o

The single  replacement  reaction  is

Mg + 2 HNO₃ →   Mg(NO₃)₂  +H₂

Explanation

Single replacement   reaction is type of chemical reaction in which element react with compound and take the place  of another element in that compound. The reaction above  is a single replacement because  Mg ( an element) react   with HNO₃( a compound)  and Mg replaces H  from HNO₃  to Mg(NO₃)₂ and H₂

The ground state electron configuration of a phosphorous atom has  three unpaired electrons. they're in the 3p sublevel. the electron configuration is: , for a total of  15 electrons.