Question

1. magnesium combines with oxygen to form magnesium oxide. a 100 - gram sample of magnesium combines with 65.8 grams of oxygen. a 10 - gram sample of magnesium combines with 6.58 grams of oxygen. which point of daltons atomic theory is supported by these findings?

all elements are composed of atoms.
in a particular compound, atoms of different elements always combine in the same way.
all atoms of the same element have the same mass, and atoms of different elements have different masses.

Explanation:

Dalton's atomic theory has several key points. One of them is that in a particular compound, atoms of different elements always combine in the same way. This is related to the law of definite proportions. When looking at the combination of magnesium and oxygen in different - sized samples (100 - gram and 10 - gram), we can check the ratio of magnesium to oxygen.
For the 100 - gram sample: mass of magnesium \(m_{Mg1}=100 - 65.8=34.2\) grams, and the ratio of \(m_{Mg1}:m_{O1}=34.2:65.8\approx1:1.92\)
For the 10 - gram sample: mass of magnesium \(m_{Mg2}=10 - 6.58 = 3.42\) grams, and the ratio of \(m_{Mg2}:m_{O2}=3.42:6.58\approx1:1.92\)
This shows that in the compound magnesium oxide, magnesium and oxygen (atoms of different elements) combine in the same ratio (same way) regardless of the sample size.
The statement "All elements are composed of atoms" is a general statement of atomic theory but does not directly relate to the combining ratio aspect shown in the problem. The statement "All atoms of the same element have the same mass, and atoms of different elements have different masses" is also a part of Dalton's theory but is more about atomic mass rather than the combining of atoms in compounds.

Answer:

In a particular compound, atoms of different elements always combine in the same way.