Arteta's side made it 11 wins from 13 league games thanks to a close-range finish from Brazilian defender Gabriel (24) in the second half at Stamford Bridge.
The Gunners are two points clear of second-placed Manchester City after the champions briefly took pole position with a win against Fulham on Saturday.
After beating Tottenham and Liverpool at home earlier this season, winning in west London was another major statement from Arsenal as their unexpected title challenge gathers pace.
"Big win for us, another step as a team. To come here against a top team and perform and actually win will give the boys even more belief," Arteta said.
"We are a really young team but we showed a lot of composure and courage to play in this stadium. I was really impressed.
"We were under pressure to go back to the top and what we did today was just phenomenal."
This was an even sweeter victory than their other landmark successes this term as it came at the expense of former Arsenal star Pierre-Emerick Aubameyang (33).
Aubameyang was anonymous in his first meeting with his old team since he was stripped of the captaincy and sold to Barcelona in January after Arteta lost patience with the Gabon forward's repeated disciplinary issues.
Exiling Aubameyang has proved an inspired move by Arteta as Arsenal look a far more unified and determined group without the sulking striker.
Booed by the travelling Arsenal fans, Aubameyang was so underwhelming that it might not be long before he becomes unwelcome at Chelsea as well.
Chelsea boss Graham Potter might also be feeling the heat soon after his side's winless league run extended to four games with a second successive top-flight defeat, prompting jeers from Blues fans at full-time.
Seventh-placed Chelsea lacked Arsenal's urgency and now trail the leaders by 13 points, with even a top four finish far from certain.
"We are not in a fantastic moment. We are not fluid in how we build our attacks. It was a huffing-and-puffing performance from us without the real quality that we need," Potter said.
"Arsenal were the better team and deserved to win. We played against a team in a really good moment, a confident team.
"They have been working together for three years and you can see the understanding. We are at the start of our process."
Arsenal have not won the title since Arsene Wenger's Invincibles in 2004, but no Gunners team has amassed more points at this stage in the Premier League era.
Asked if he believes Arsenal can maintain their challenge, Arteta said: "Look at what Manchester City have done for the last six years. We have to be very respectful of that.
"We are getting better. We are in contention so lets enjoy that tonight. It's going to be a long marathon."
