Concatenate formula fields and domain name

I’d like to combine two fields and another field that contains a string text of @domain.com to output to field called email.

I’d like to insert a period between the first and last name fields too. The final output should look like:

john.smith@domain.com

I’m not sure how I should create a field for the “.” and the “@domain” in order to create the necessary output.

i started with this but not sure how I’d create with a formula.

First_Name__c & " " &
Last_Name__c & “ ” &

@domain.com

thank you!