Atlanta, who meet Paris Saint-Germain in the Champions League quarter-finals, finish in third place for their second consecutive season.
Immobile needs just one more goal against Napoli on Saturday to equal the scoring record of 36 goals for a single campaign achieved by Gonzalo Higuain, playing for Napoli, in the 2015-16 season.
Portuguese ace Ronaldo has won the Golden Shoe four times during his illustrious career, the last of those coming in the 2014-15 season, when he scored a remarkable 48 goals in 35 La Liga games with Real Madrid.
Immobile will also win the European Golden Shoe for the continent's top scorer this term, having overtaken Bayern Munich striker Robert Lewandowski's tally of 34 in midweek.
In the San Siro, Zlatan Ibrahimovic missed a penalty but scored his 10th league goal since January as AC Milan finished with a 3-0 win over Cagliari.