Chem Fall 2025 Sem Exam

Dalton (1803)

proposed atomic theory which was that atoms are smallest part of an element; are indivisible and indestructible; atoms of 1 elements are smae; atoms of diff elements are diff

Thomson (1897)

plum pudding; discovered electrons using cathode ray tube

Rutherford (1911)

gold foil experiment where he figures out there is a nucleus and that most of the atom is empty space

Bohr (1913)

organized electrons into rings;  electrons can gain a fixed amount of energy (quantum) and the electrons will jump up to a higher energy level. Electrons will return to a lower energy level and colorful light will be emitted.

Heisenberg & Schrodinger (1927)

Heisenberg: It is impossible to know the speed & the position of a subatomic particle at the same time. Schrogdinger had an equation. Both ideas come tg and quanatum mechanical model is formed and divided shells into subshells (1s, 2s, etc)

Shielding effect

when inner electrons block some of the nucleus’s pull, so outer electrons feel a weaker attraction.