When ads are too close, they tend to result in accidental clicks and can negatively impact the performance of each ad. Google recommends an adequate distance between the ads.
See: https://support.google.com/adsense/answer/1346295
Recommendations:
- Observe a distance of at least 1 screen height between ads on mobile.
- Only 1 ad unit should be visible in the viewport at once.
- Deploy one ad unit at the bottom just above the fold, skip a screen height > then another ad unit, another screen height > another unit, etc, up to 5 units.
- Smaller ad sizes usually perform worse than the bigger ones, so go for 300×250 where applicable.
- Do not implement more than 5 ad units per page unless extremely necessary (e.g. lengthy content)
- Keep content-to-ad balance. Google recommends more content than ads per page.