Lesson 2 : History and Proponents of Atomic Model

Who proposed the concept of atoms?

Democritus

What does "atomos" mean?

Uncuttable or indivisible.

Who proposed the The Plum-Pudding Model?

J.J. Thomson

State that an atom is a sphere of positive particles to which negative particles are embedded.

J.J. Thomson

Who conducted the Gold Foil Experiment and proposed the Nuclear Model?

Ernest Rutherford.

Who proposed the Planetary Model of the atom?

Niels Bohr.

Who introduced the Quantum Mechanical Model of the atom?

Erwin Schrodinger.

Who discovered the neutron?

James Chadwick.

Who discovered the electron through the cathode ray experiment?

J.J. Thomson.

Who found the charge of the electron using the oil-drop experiment?

Robert Millikan.

It States that different samples of the same compound always contain its constituent elements in the same proportion by mass.

Law of Definite Proportions

If two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers

Law of Multiple Proportions

Matter can be neither created nor destroyed.

Law of Conservation of Mass

Negatively Charged particles

Electron

Positively Charged particles

Proton

No charge particle

Neutron

Its a dense central core within the atom

Nucleus

What force holds an atom together?

Electromagnetic force

What is the mass of an Electron?

9.11X10^-28

What is the mass of a Proton?

1.67X10^-24

What is the mass of a Neutron?

1.67X10^-24

It Refers to the number of protons in the nucleus of each atom of an element

Atomic Number

It is the total number of neutrons and protons present in the nucleus of an atom of an element.

Mass Number

Its when an atoms has an element that have the same number of protons and the same number of electrons but different numbers of neutrons

Isotopes

The different elements have the same atomic weight or mass number but different atomic number is called?

Isobar

The different elements having the same number of neutrons called?

Isotones

A rule for electron configuration that states, two electrons occupying an orbital should have opposite spins.

Pauli’s Exclusion Principles

This states that electrons should enter the orbitals of a given singlet with same spin before any pairing is done.

Hund’s Rule

states that electron should enter orbitals of lowest energy before filling higher energy levels.

Aufbau Principle