"All I Have" also represented Lopez's previous highest debut, having arrived at No. 25 the week of Dec. 28, 2002.
"On the Floor" marks Lopez's 10th Hot 100 top 10, a sum that includes four No. 1s. She had last reached the top 10 as a featured artist on LL Cool J's "Control Myself" in 2006.
The song previews "Love?," Lopez's seventh studio album due Apr. 19.
Divas dominate this week's Hot 100 headlines, as Lady Gaga's "Born This Way" spends a third week at No. 1, dating to its debut on top two weeks ago.
Though it's off 44% in downloads to 286,000, according to Nielsen SoundScan, the song remains at No. 1 on Digital Songs. Radio activity surges, as "Born" gains by 21% on Radio Songs (101 million, according to Nielsen BDS), where it holds at No. 4.
Lady Gaga's 'Born' This Way Video Premieres
The song passes a million in digital sales - its cumulative sum stands at 1,243,000 - making it the fifth-best-selling download this year.
At three weeks atop the Hot 100, "Born" ties Gaga's debut single, "Just Dance," featuring Colby O'Donis (2009), for the longest of her three chart reigns. (Her second No. 1, "Poker Face," ruled the April 11, 2009, Hot 100).
Like "Born," Cee Lo Green's "F**k You (Forget You)," at No. 2 for a second week, registers a sharp digital decline - down 39% to 252,000 - while building in airplay. The song claims Airplay Gainer honors on the Hot 100 for a second consecutive week, bounding into the top 10 (14-6) on Radio Songs (80 million in audience, up 28%).
Bruno Mars' "Grenade" holds at No. 3 on the Hot 100 and P!nk's "F**kin' Perfect" rebounds 6-4.
Rihanna's "S&M" forces a 7-5 advance, granting the singer her 13th top five Hot 100 hit. In the chart's 52-year history, only four other solo females have notched more top five tracks: Madonna (28), Mariah Carey (26), Janet Jackson (24) and Whitney Houston (19). (Rihanna ties the top five tallies of Beyonce and Olivia Newton-John).
Katy Perry's "Firework" falls 5-6, and Enrique Iglesias' former No. 4-peaking "Tonight (I'm Lovin' You)," featuring Ludacris and DJ Frank E, rises 9-7. As previously reported, the song becomes Iglesias' first No. 1 on the Pop Songs radio airplay chart.
Perry doubles up in the top 10, as "E.T.," featuring Kanye West, rockets 28-8 with Digital Gainer accolades. The cut roars 12-4 on Digital Songs (170,000, up 42%) and enters Radio Songs at No. 57 (20 million, up 194%).
Dr. Dre's "I Need a Doctor," featuring Eminem and Skylar Grey, continues its Hot 100 yo-yoing, descending 4-10. Three weeks ago, the song started at No. 5 before exhibiting expected sharp second-week sales declines and plummeting to No. 32. Following Dr. Dre's appearance at the Grammy Awards Feb. 13, the track rebounded to No. 4 last week.
Twelve additional debuts join Lopez's "Floor" in entering the Hot 100.
With three new entries, the "Glee" cast ups its count to a record-extending 120 total Hot 100 hits. (Two weeks ago, it passed Elvis Presley's 108 charted titles). The ensemble enters with remakes of Human League's "Don't You Want Me" (No. 49), Jamie Foxx's "Blame It (On the Alcohol)" (No. 55) and Ke$ha's "TiK ToK" (No. 61).
'Glee' Gets Sick Over Ke$ha, Blames It 'On the Alcohol'
The TV troupe releases "Glee: The Music, Volume 5" next Tuesday (March 8), featuring its first two original songs: the uptempo, Max Martin-co-written "Loser Like Me" and the Lea Michele-sung ballad "Get It Right" (both expected to impact the Hot 100 in two weeks).
Other Hot 100 debuts include Wiz Khalifa's "On My Level," featuring Too $hort; "Someone Like You" (No. 65) and "Set Fire to the Rain" (No. 88), both from Adele's "21," the Billboard 200's new No. 1; and, Aaron Lewis' "Country Boy," featuring George Jones and Charlie Daniels.
The lattermost song marks Daniels' first visit to the Hot 100 since 1982.