what are the three assumption when adding of oxide percentage to 128% in the calculation of elements because most elements bound to oxygen in the form of silicate. The elements are silicon, aluminum, iron calcium magnesium sodium, potassium and titanium have different weight of elements in crust and different weight of oxide in the crust
1. The assumption that the sum of oxide percentages for all elements in the crust adds up to 128%. This assumption is made to account for the fact that most elements are bound to oxygen in the form of silicates, which are common in the Earth's crust.
2. The assumption that each element has a different weight in the crust and a different weight as an oxide in the crust. This is important to consider when calculating the total oxide percentage and understanding the distribution of elements in the crust.
3. The assumption that the elements listed (silicon, aluminum, iron, calcium, magnesium, sodium, potassium, and titanium) are representative of the overall composition of the Earth's crust. While these elements are common in the crust, there are many other elements present in smaller amounts that also contribute to the overall composition.