I think Oxygen is the best answer.
Answer:
Both physical and chemical weathering, along with erosion, can change Earth's surface as physical weathering allows breakdown of rock into smaller pieces, these pieces can be move from one place to another through water, wind or ice (erosion), and when the smaller pieces will settle down at a place, rain water can react with the soil or smaller rock pieces to form rock minerals.
For example: Running water, wind, and rapid heating/cooling allows the rocks to break down into smaller pieces or grains (physical weathering), then the small grains are transported and settled away from the source area through wind or river (erosion), and at the end the surface area exposed to air for chemical weathering.
To have an overall positive or negative charge. (as opposed to neutral one)
