Evolving Atomic Theory (names) Flashcards
What is Dalton’s Atomic Theory?
All matter is composed of tiny, indivisible particles called atoms. Atoms of an element have identical properties, while atoms of different elements have different properties. Atoms of two or more elements can combine in constant ratios to form new substances.
Example: H2O ratio 2:1 → water, H2O ratio 2:2 → H2O2 → hydrogen peroxide.
What did J.J. Thompson discover?
J.J. Thompson is credited with the discovery of electrons. He proposed the ‘raisin bun’ model or ‘plum pudding’ model of the atom, where the atom is a sphere that is positive, with negative electrons embedded in it like raisins in a bun.
What is the significance of Ernest Rutherford’s work?
Ernest Rutherford stated that atoms have a nucleus which is positive and takes up most of the mass. Most of the atom is empty space occupied by moving electrons(negative). He also proposed the idea of protons.
What did Neils Bohr propose in 1913?
Electrons move in circular orbits around the nucleus and cannot exist between orbits.
What did James Chadwick discover in 1932?
The nucleus must contain heavy neutral particles called neutrons to account for all of the atom’s mass.
What is the quantum mechanical model proposed by Schrodinger/de Broglie in 1930?
Electrons have distinct energy levels, but their exact locations are not defined; instead, their probable location in a region of space can be predicted.
