Invited review given at the JENAM 2002 in Porto, Workshop ISM, eds. M.A. de Avillez & D. Breitschwerdt, Kluwer.
astro-ph/0212104.

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Abstract. Groups and clusters contain a large fraction of hot gas which emits X-ray radiation. This gas yields information on the dynamical state and on the total mass of these systems. X-ray spectra show that heavy elements are present in the gas. As these metals must have been produced in the cluster/group galaxies and later transported into the gas, the metallicity is a good tracer for the transport processes. Several possible processes, that transport gas from the small potential wells of the galaxies into the clusters and groups, are discussed.

Table of Contents

GAS PROPERTIES

GAS DISTRIBUTION, DYNAMICAL STATE AND MASS DETERMINATION

INTERACTION BETWEEN ISM AND ICM/IGM

SUMMARY

REFERENCES