How does atelectasis and pneumothorax present differently on an ap chest x-ray?

Black and white : Pneumothorax would appear black as air looks like this on x-ray and atelectasis is white. Pneumothorax is air outside the lung and causes lung collapse by pressure while atelectasis is lung that has collapsed together usually by mucous and some loss of surface tension in the air sacs - called alveoli.

Very different: Atelectasis is a portion of the lung with no air in it and appears as a consolidation on cxr. Pneumothorax is collapsed lung with air on the outside of the lung occupying the pleural space and appears as a large black space on a cxr.

Surroundings: The lung portion in both can appear as consolidation. Atelectasis is a portion of deflated lung with no air in it and appears whitish/consolidation on cxr. Generally, the remaining inflated lung will increase expansion. Pneumothorax is deflated/collapsed lung with air on the outside of the lung and appears as a large black space on a cxr. Generally, air will cause progressive collapse of lung.