Question

Iron, an element with the chemical symbol Fe, is an important element. It is used to make steel and is part of the substance that transports oxygen throughout the human body.

Which statement about Fe is supported by the modern atomic theory but not John Dalton’s theory?
The element iron is composed of small particles called atoms.
The electrons of iron have probable locations in a region of space around the nucleus.
Iron atoms combine with other atoms in whole number ratios to form compounds.
Chemical reactions that involve iron do not create new atoms of iron.

Answer 1

"The electrons of iron have probable locations in a region of space around the nucleus."

Why: Dalton's model treated atoms as indivisible, solid particles and did not include electrons or electron clouds. Modern atomic theory (quantum mechanics) describes electrons as existing in orbitals — regions of space with a probability of finding an electron — a concept Dalton did not have. The other statements (atoms exist, whole-number combination ratios, atoms not created/destroyed in chemical reactions) were part of Dalton's theory.