  The dusty winds of cool evolved stars are a major contributor of the newly
synthesised material enriching the Galaxy and future generations of stars.
However, the details of the physics and chemistry behind dust formation and
wind launching have yet to be pinpointed. Recent spatially resolved
observations show the importance of gaining a more comprehensive view of the
circumstellar chemistry, but a comparative study of the intricate interplay
between chemistry and physics is still difficult because observational details
such as frequencies and angular resolutions are rarely comparable. Aiming to
overcome these deficiencies, ATOMIUM is an ALMA Large Programme to study the
physics and chemistry of the circumstellar envelopes of a diverse set of
oxygen-rich evolved stars under homogeneous observing conditions at three
angular resolutions between ~0.02"-1.4". Here we summarize the molecular
inventory of these sources, and the correlations between stellar parameters and
molecular content. Seventeen oxygen-rich or S-type asymptotic giant branch
(AGB) and red supergiant (RSG) stars have been observed in several tunings with
ALMA Band 6, targeting a range of molecules to probe the circumstellar envelope
and especially the chemistry of dust formation close to the star. We
systematically assigned the molecular carriers of the spectral lines and
measured their spectroscopic parameters and the angular extent of the emission
of each line from integrated intensity maps. Across the ATOMIUM sample, we
detect 291 transitions of 24 different molecules and their isotopologues. This
includes several first detections in oxygen-rich AGB/RSG stars: PO v=1, SO2
v1=1 and v2=2, and several high energy H2O transitions. We also find several
first detections in S-type AGB stars: vibrationally excited HCN v2=2,3 and SiS
v=4,5,6, as well as first detections of the molecules SiC, AlCl, and AlF in W
Aql...
