Soto is batting .246 with 21 home runs, 46 RBI and 62 runs scored this season. The outfielder currently leads the majors with 91 walks and was crowned the Home Run Derby champion during the All-Star break last month.
Bell is batting .301 with 14 home runs with 57 RBIs.
In return, the Nationals will receive first baseman and designated hitter Luke Voit, shortstop CJ Abrams, outfielders Robert Hassell III and James Wood, left-handed pitcher MacKenzie Gore, and right-handed pitcher Jarlin Susana.
All signs pointed to Soto being on the move after he reportedly rejected a 15-year, $440 million extension offer from the Nationals last month.
The two-time All-Star from the Dominican Republic joins a San Diego lineup that includes shortstop Fernando Tatis Jr. and third baseman Manny Machado and together they will make up one of the most fearsome lineups in baseball.
"It's pretty impressive to have those three types of guys on one team in the same lineup," Padres first baseman Wil Myers told reporters on Tuesday, according to ESPN.
"Excited to see that trio, hopefully in the next week or two."
The Padres are currently 12 games back of the Los Angeles Dodgers in the NL West and will look to Soto to help them reach the postseason for the first time since the pandemic-shortened 2020 season, when they were eliminated by the eventual champion Dodgers.
The Padres have won NL pennants in 1984 and 1998 but have never won the World Series.