Series

Let v_(1) be the frequency of series limit of Lyman series, v_(2) the frequency of the first line of Lyman series and v_(3) the frequency of series limit of Balmer series. Then which of the following is correct ?

There are four radioactive decay series called thorium (4n) , uranium (4n + 2) actinium (4n + 3) and neptunium (4n + 1) series. Neptunium series is artificial while other three series are natural. The end productsd of each radioacitve decay series have stable nuclei. All natural decay series terminate at lead but neptunium or artificial series terminate at bismuth. ._(86)Rn^(219) is a member of actinium series. Another member of same series is