Based on wind speed in historical best track data...

Chantal formed further south than any other tropical storm this early in the year (July 10th or earlier) in the satellite era. (For reference, current best track data, subject to revision, has Chantal becoming a tropical storm at 9.7N 46.1W on July 8th at 0Z) There were only two other tropical storms that formed further south than Chantal since 1851, an unnamed tropical storm (02L) on July 1st, 1901 (9N 54W) and an unnamed tropical storm (02L) on June 25th, 1933 (9N 45.2W), which later became a hurricane.

Chantal formed further east than any other tropical storm this early in the year (July 10th or earlier) not named Bertha in the satellite era. A total of four storms since 1851 have formed further east than Chantal. In the satellite era, there were only two instances and both were named Bertha. Tropical Storm Bertha (02L) on July 3rd, 2008 (13.1N 24W) and Tropical Storm Bertha (02L) on July 5th, 1996 (11N 39W). Both later became major hurricanes. Prior to the satellite era there were two other storms. One was the previously mentioned unnamed tropical storm (02L) on June 25th, 1933 (9N 45.2W), which later became a hurricane. The other, an unnamed tropical storm (01L) in 1938, which later became a hurricane, is more likely to be associated with a late season storm, occurring in the first few days of January in the northern Atlantic. It became a tropical storm on January 3rd (27.5N 35.3W), although it was listed in best track data as becoming an extratropical storm on January 1st (32.3N 40.6W) with tropical storm force winds.

Looking at the data for the entire year, many storms have of course formed further east of where Chantal formed, though there are still few that have formed further south. (List below includes storms previously mentioned.) This list shows where a storm became a tropical storm and the name reflects the highest development it achieved.

Four to the west of Chantal:

Hurricane Unnamed (05L) - September 1st, 1878 - 8.5N 54.2W
Tropical Storm Unnamed (02L) - July 1st, 1901 - 9.0N 54.0W
Tropical Storm Fran (07L) - August 13th, 1990 - 9.0N 53.6W
Major Hurricane Unnamed (03L) - August 13th, 1893 - 9.6N 50.5W

Five to the east of Chantal:

Hurricane Unnamed (02L) - June 25th, 1933 - 9.0N 45.2W
Hurricane Unnamed (06L) - October 26th, 1896 - 8.7N 44.2W
Tropical Storm Dolly (04L) - August 29th, 2002 - 9.7N 32.2W - Same latitude as Chantal
Hurricane Unnamed (03L) - September 16th, 1902 - 7.7N 30.8W
Major Hurricane Ivan (09L) - September 3rd, 2004 - 9.7N 30.3W - Formed at the same latitude as Chantal, although it later dipped slightly southward to 8.9N