Diatoms are microscopic photosynthesizing algae (micro-algae) that have intricate outer walls made of silica in an overlapping soap box-like fashion.
They undergo both sexual and asexual reproduction cycles.
Examples- Navicula, Rutilaria, Eunotia, Cyclotella, Epithemia, etc.
Chrysophytes
Chrysophytes are a large group of unicellular or colonial golden-brown algae or phytoplankton found mostly in freshwater.
Diatoms (Bacillariophyceae), yellow-green algae (Xanthophyceae), and golden-brown algae (Chrysophyceae) belong to Chrysophytes.
Chrysophytes were earlier used to describe all diatoms and multicellular brown algae, but are now used to describe closely related members based on the flagella structure.
Diatoms can be referred to as chrysophytes but they are not relevant to each other.