* When was hydrogen recognized as a distinct substance?
* Hydrogen's isotopes are the only ones that have distinct names. Which of the following is NOT an isotope of hydrogen?
* How much of the mass of the observable universe is made of hydrogen?
* A cubic foot of hydrogen in a balloon will lift about how much weight?
* Neon is classified in this group of elements.
* In a vacuum discharge tube, what color does neon glow?
* What is the proportion of neon in air?
* What is the atomic symbol for iron?
* Iron's rank (by weight) in the Earth's crust is:
* Wrought iron contains iron and what other element?
* What is iron's atomic number?
* What is its melting point?
* Oxygen forming the molecule O3 is called:
* The unstable isotope, O-15, has a half life of about:
* Molecular oxygen (O2) comprises what percentage of the Earth's atmosphere (at sea level)?
* What life process of most life forms requires oxygen?
* Uranium has how many isotopes?
* Uranium was first isolated as an element in:
* Uranium was used in the two atomic bombs dropped on Japan in WWII; one bomb used is as the main explosive, the other as a tamper around a plutonium core. On which city was the strictly-uranium bomb dropped?
* Which of the following minerals does NOT contain uranium?