The atmosphere of Planet Venus is made up of thick and yellowish clouds of

The atmosphere of Venus is the densest among the terrestrial planets and is primarily composed of carbon dioxide [1]. It is characterized by a thick, permanent layer of clouds that totally obscure the planet's surface [1]. These clouds are composed of droplets of concentrated sulfuric acid (H2SO4) [1]. The sulfuric acid is formed through chemical reactions involving sulfur dioxide (SO2) and water vapor (H2O), often triggered by photo-oxidation from solar ultraviolet radiation. These clouds are highly reflective, contributing to the planet's high albedo and intense greenhouse effect [1]. While traces of other substances like nitrogen and water vapor exist, the defining chemical component of the visible, yellowish cloud deck is sulfuric acid.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 2: The Solar System > Venus > p. 28