Yes, Thanos snaps are multiplicative.
But I think we can establish that objects get eliminated in their entirety and not on an atomic scale, or else the snap should have killed way more than half of the people considering that about half their cells just committed sudoku.
Btw if it worked on an atomic scale:
We assume Thanos only wants to snap the gold that has use for humans. We mined around 210,000 tonnes of gold and known reserves of gold hold another roughly 80,000 tonnes. That makes 290,000 tonnes total. 290,000 tonnes of gold have around 8.87 * 1032 gold atoms, so Thanos would need to snap on average log_2(8.87*1032) + 2 = 112 times to eradicate all of that gold.
Note that the total amount of gold on Earth is much larger than that (unknown deposits, deeps in the crust, in the core), but that would get rid of the stuff we actually care about.
Fun fact. Hieroglyphs can be written left-to-right or right-to-left. You have to distinguish the direction they should be read by the facing of the animal/creature/human used as a character. They will always "look" towards the beginning of the sentence, so in the depicted case, the intended direction is left-to-right.