Hydrogen line, an Uncommon card

The card carries these facts from its Wikipedia article.

• It is produced by a spin-flip transition, which means the direction of the electron's spin is reversed relative to the spin of the proton.
• This is a quantum state change between the two hyperfine levels of the hydrogen 1 s ground state.
• The electromagnetic radiation producing this line has a frequency of 1420.405751768 MHz, which is equivalent to a wavelength of 21.106114054160 cm in a vacuum.

Rarity in WikiCards follows a year of Wikipedia page views: the most read articles become Epic and Legendary cards. The Hydrogen line article was read about 63,000 times in a year. ATK comes from the length of the article and DEF from its quality, so this card hits with 71 and blocks with 54: each hit it takes is cut by 22 %.

Open packs. Each pack holds five cards drawn from real Wikipedia articles, the rarest last, and the fifth card is always Rare or better. The odds are shown in the game. A free pack arrives every hour and two can wait, and the Coins you win in duels buy more packs.

The cards just above and just below Hydrogen line in the power ranking, all domains together.