Which sequence of historic developments led to the modern model of the atom?

Regents Chemistry Exam June 2025 Question 1

1 Which sequence of historic developments led to the modern model of the atom?

(1)  electrons in shells outside a nucleus, hard sphere, mostly empty space

(2)  electrons in shells outside a nucleus, mostly empty space, hard sphere

(3)  hard sphere, electrons in shells outside a nucleus, mostly empty space

(4)  hard sphere, mostly empty space, electrons in shells outside a nucleus

Solution:

The first theory proposed that atoms are hard spheres. Then, gold foil experiment showed that atoms are made of mostly empty space with a small dense nucleus in the middle. Finally, Bohr model shows that there are electrons that are located in shells outside the nucleus. Choice 4 is the correct answer choice.

LINKS:

Regents Chemistry Guides and Solutions

Chemistry Tutoring

More Regents Chemistry Practice