How many electrons are needed for an atom to be stable

8 electrons are needed

eight electrons are needed for an atom be stable.

Catalyst increase the rate of reaction

Catalyst decrease the activation energy needed to start a reaction

They are not used up in the reaction

Catalyst are not very specific

Explanation:

From the basic chemistry it is known Catalysts are substance that accelerates the rate of reaction without altering the nature of reaction.

Catalysts decreases the energy required for activation, in order to make collisions quicker.

Then, Catalyst just alters the rate of reaction alone and doesn't takes part in the chemical reaction.

Some catalysts are specific. But in general most of the catalysts are not specific in nature.