$word_{count}$: 200

Rydberg formula: 1/lambda = $RZ^2$(1/$n1^2$ - 1/$n2^2$), R = 1.097 x 10^7 $m^{-1}$. Five series: Lyman (n1=1, UV, 91.2-121.6 nm), Balmer (n1=2, visible, 364.7-656 nm), Paschen (n1=3, IR), Brackett (n1=4, IR), Pfund (n1=5, far IR). Total lines from level n: n$\frac{n-1}{2}$. Lines in specific series from n: n - n1. First line = longest wavelength = smallest energy gap (n2 = n1+1). Series limit = shortest wavelength = largest energy gap (n2 = infinity). For each series: $lambda_{limit}$ = $n1^2$/R. Energy shortcut: E(eV) = 1240/lambda(nm). H-alpha (656 nm, red), H-beta (486 nm, blue-green), H-gamma (434 nm, violet), H-delta (410 nm, violet). An excited atom can emit multiple photons if it cascades through intermediate levels. Maximum photons from n = n-1 (one step at a time). Absorption spectrum at room temperature shows only ground-state transitions (fewer lines than emission spectrum).