Which of these astronauts was not one of the Mercury Seven?

The Mercury Seven were the group of seven astronauts selected to fly spacecraft for Project Mercury. They are also referred to as the Original Seven and Astronaut Group 1. Their names were publicly announced by the National Aeronautics and Space Administration (NASA) on April 9, 1959. These seven original American astronauts were Scott Carpenter, Gordon Cooper, John Glenn, Gus Grissom, Wally Schirra, Alan Shepard, and Deke Slayton. The Mercury Seven created a new profession in the United States, and established the image of the American astronaut for decades to come.

Neil Alden Armstrong (August 5, 1930 – August 25, 2012) was an American astronaut and aeronautical engineer, and the first person to walk on the Moon. He was also a naval aviator, test pilot, and university professor.