1. What color will an interstellar gas cloud composed of hydrogen glow, and why? 2. What is an element? List the names of five different elements, and briefly explain what makes them different from...

1. What color will an interstellar gas cloud composed of hydrogen glow, and why?

2. What is an element? List the names of five different elements, and briefly explain what makes them different from each other.

3. How are the three isotopes of hydrogen different from each other?