Atomic Model, 2nd qtr.

im killing myself

Leucippus and Democritus

proposed that matter is made of tiny, indivisible particles called “atomos”, ignored for over 200

Aristotle

proposed that everything in the world was made up of the 4 main elements, fire, wind, earth, water. was preferred theory

“Dalton’s Atomic Theory”

proposed by John Dalton which is considered the starting point of the modern atomic theory. Deduced that all elements are composed of atoms. they are indivisible and indestructible particles.

Law of conservation of mass & law of constant composition/law of definite proportions

what Dalton’s atomic theory was based on. first proposed by french chemist Antoine Lavoisier and Joseph Louis Proust respectively.

Plum Pudding Model

emerged as a result of the discovery of negatively charged components inside the atom. Proposed that atoms were made from a positively charged substance with negatively charged electrons scattered about. First described by physicist J.J Thompson, referred later to  as  electrons.

Nuclear Model

proposed by Ernest Rutherford, Hans Geiger, and Ernest Marsden. States that the atom consists of a dense positive center called the nucleus that is orbited by negatively charged electrons. later discovered positively charged subatomic particles in the atom’s nucleus, naming them protons.

neutron

discovered by James Chadwick. no charge.

proton

discovered by Ernest Rutherford. positively charged.

electron

discovered by J.J. Thompson. Negatively charged.

Planetary Model

first established the existence of an atom’s nucleus, vaguely understood. Changed in 1913, when Niels Bohr studied the emission line of hydrogen. Says that electrons move around in definite orbits around the nucleus, much like how planets circle the sun.

Wave model

According to this, electrons do not move about an atom in a definite path. It is impossible to determine the exact location of an electron. This was formulated by Erwin Schrodinger.

Atomos

To democritus, atoms were small, hard particles that were all made of the same material but different sizes.

The Nuclear Symbol

shows the symbol of an element, its mass number, and its atomic nnumber.

A

Mass number

Z

Atomic number

X

symbol of the element

Mass Number/A

p⁺ + n⁰

Atomic number

Z = p⁺ = e^-

n⁰/ neutrons

A - p⁺

e^-

number of electron

p⁺

number of protons

n⁰

number of neutrons