IPS1 - (A2) - Atom and the Development of Atomic Models

Proverbs 16:3

atomos

The word atom comes from the ancient Greek word "___", which means "uncuttable" or "indivisible."

uncuttable" or "indivisible

The word atom comes from the ancient Greek word "atomos", which means ___ or ___

Atom

The smallest unit that retains the properties of an element.

Dalton's Theory

This theory states the all matter is composed of atoms and these cannot be made or destroyed.

0.00054858 amu

[FUNDAMENTAL PARTICLES OF MATTER]

• Mass of Electron (e-) = ____ ?

1.0073 amu

[FUNDAMENTAL PARTICLES OF MATTER]

• Mass of Proton (p+) = ___ ?

1.0087 amu

[FUNDAMENTAL PARTICLES OF MATTER]

• Mass of Neutron (n) = ____ ?

Z

Symbol for Atomic Number

Protons

The number of ___ in the nucleus of an atom determines its identity; this number is known as the ATOMIC NUMBER of that element.

A

Symbol for Mass Number

mass number

The ___ of an atom is the sum of the number of protons and the number of neutrons in its nucleus

Isotopes

These are atoms of the same element with DIFFERENT masses.

Isotopes

They are atoms containing the same number of protons but different numbers of neutrons.

Protium ( A= 1)

[ISOTOPES]

Hydrogen-1 is also known as___

Deuterium ( A= 2)

[ISOTOPES]

Hydrogen-2 is also known as___

Tritium ( A = 3)

[ISOTOPES]

Hydrogen-3 is also known as___

● Protium

● Deuterium

● Tritium

[ISOTOPES]

• Three isotopes of hydrogen such as ___

● Carbon-12

● Carbon-13

● Carbon-14

[ISOTOPES]

Three isotopes of CARBON

Nuclide symbol

This symbol represents the composition of the nucleus.

[Element name] - [Mass number]

Another way of representation for isotopes

atomic weight

The ___ of such an element is the weighted average of the masses of its isotopes.

FRACTIONAL NUMBERS (decimal)

Atomic weights are ______ [fractional numbers or integers]

Isobars

Atoms that have the SAME MASS but DIFFERENT ATOMIC NUMBER/PROTONS.

Isotones

Atoms that have the SAME NUMBER OF NEUTRONS but DIFFERENT ATOMIC NUMBER/PROTONS.

Leucippus and Democritus (500 BC)

[DEVELOPMENT OF ATOMIC MODELS]

• They introduced the idea of atom, which came from the Greek word "ATOMOS" = uncuttable or indivisible.

Leucippus and Democritus (500 BC)

[DEVELOPMENT OF ATOMIC MODELS]

They believed atoms were SOLID, INDIVISIBLE spheres.

Aristotle

[DEVELOPMENT OF ATOMIC MODELS]

• He rejected the atom concept and proposed that matter is made of FOUR ELEMENTS (earth, water, air, fire)

John Dalton

[DEVELOPMENT OF ATOMIC MODELS]

• He proposed the SOLID SPHERE (BILLIARD BALL) model.

John Dalton

[DEVELOPMENT OF ATOMIC MODELS]

He proposed that atoms are SOLID SPHERES but NOT indivisible.

Humphry Davy

[DEVELOPMENT OF ATOMIC MODELS]

• He showed that elements in a compound are held together by ELECTRICAL FORCES.

Michael Faraday

[DEVELOPMENT OF ATOMIC MODELS]

He demonstrated the relationship between the AMOUNT OF ELECTRICITY used in electrolysis and the AMOUNT OF CHEMICAL REACTION that occurs.

George Stoney

[DEVELOPMENT OF ATOMIC MODELS]

• He first used the term "electrons", describing them as ELECTRIC IONS.

Joseph John Thomson

[DEVELOPMENT OF ATOMIC MODELS]

• He provided the MOST CONVINCING evidence of ELECTRONS.

Joseph John Thomson

[DEVELOPMENT OF ATOMIC MODELS]

He proposed the PLUM PUDDING MODEL

• → atoms are positively charged spheres with negatively charged electrons embedded.

Joseph John Thomson

[DEVELOPMENT OF ATOMIC MODELS]

He proposed the CATHODE-RAY TUBE EXPERIMENT.

Robert Millikan

[DEVELOPMENT OF ATOMIC MODELS]

• He determined the CHARGE of electrons using the OIL-DROP EXPERIMENT.

Hantaro Nagaoka

[DEVELOPMENT OF ATOMIC MODELS]

• He proposed SATURN-LIKE MODEL, that atoms resemble Saturn, with a large positively charged sphere at the center and electrons revolving around it like Saturn's rings.

Eugen Goldstein

[DEVELOPMENT OF ATOMIC MODELS]

• In his CANAL RAYS EXPERIEMENT, using a CATHODE-ray tube, he discovered that the tube also generates a stream of POSITIVELY charged particles.

Eugen Goldstein

[DEVELOPMENT OF ATOMIC MODELS]

In his CANAL RAYS EXPERIEMENT

→ he discovered that these positive rays (canal rays), or positive ions, are created when gaseous atoms in the tube lose electrons.

Ernest Rutherford

[DEVELOPMENT OF ATOMIC MODELS]

• In his SCATTERING EXPERIMENT (Gold Foil), he bombarded thin gold foil with ALPHA particles. Quite unexpectedly, nearly all of the a-particles passed through the foil with little or no deflection.

Ernest Rutherford

[DEVELOPMENT OF ATOMIC MODELS]

He concluded that atoms consist of very small, very dense POSITIVELY charged NUCLEI surrounded by clouds of electrons at relatively large distances from the nuclei.

Nuclear Model

[DEVELOPMENT OF ATOMIC MODELS]

• Proposed by Ernest Rutherford (1911) after the Gold Foil Experiment, this showed that the positive charge is localized in a tiny central region called the NUCLEUS.

Henry Gwyn Jeffreys Moseley

[DEVELOPMENT OF ATOMIC MODELS]

• He studied X-rays emitted by various elements.

Henry Gwyn Jeffreys Moseley

[DEVELOPMENT OF ATOMIC MODELS]

• He concluded that the number of PROTONS in the nucleus determines the identity of an element. This number is called the ATOMIC NUMBER.

James Chadwick

[DEVELOPMENT OF ATOMIC MODELS]

• He bombarded BERYLLIUM with high-energy alpha particles which produced neutral particles identified as NEUTRONS.

Beryllium

[DEVELOPMENT OF ATOMIC MODELS]

James Chadwick bombarded ___with high-energy alpha particles which produced neutral particles identified as NEUTRONS.

Niels Bohr

[DEVELOPMENT OF ATOMIC MODELS]

He described the electron of a hydrogen atom as revolving around its nucleus in one of a discrete set of circular orbits.

Bohr's Planetary Model

[DEVELOPMENT OF ATOMIC MODELS]

This model describes that:

● Each orbit thus corresponds to a definite energy level for the electron

● When an electron is excited from a lower energy level to a higher one, it absorbs a definite (quantized) amount of energy

● Electrons occupy only certain energy levels in atoms

Louis de Broglie

[DEVELOPMENT OF ATOMIC MODELS]

• He proposed the idea of WAVE-like nature of electrons. Electrons can be treated as WAVES more effectively than as small compact particles traveling in circular or elliptical orbits.

Quantum Mechanics

[DEVELOPMENT OF ATOMIC MODELS]

• This field of study is based on the WAVE properties of matter.

• This treats electrons not as tiny particles in orbits, but as waves confined in atoms.

Werner Heisenberg's Uncertainty Principle

[DEVELOPMENT OF ATOMIC MODELS]

This principle stated that it is IMPOSSIBLE to determine simultaneously the exact momentum and the exact position of an electron.

standing wave

[DEVELOPMENT OF ATOMIC MODELS]

The mathematical approach of quantum mechanics involves treating the electron in an atom as a ___.

Erwin Schrödinger's Wave Equation

[DEVELOPMENT OF ATOMIC MODELS]

• This equation estimates the POSITION of electrons and QUANTIFIES energy levels.

Atomic Orbitals

[DEVELOPMENT OF ATOMIC MODELS]

A region of space in which the probability of finding an electron is HIGH.

Erwin Schrödinger

[DEVELOPMENT OF ATOMIC MODELS]

• He proposed the MODERN ATOMIC MODEL based on ELECTRON CLOUD MODEL and QUANTUM MECHANICAL MODEL.

● Electron Cloud Model

● Quantum Mechanical Model

[DEVELOPMENT OF ATOMIC MODELS]

Erwin Schrödinger proposed the MODERN ATOMIC MODEL based on ___ and ___ ?