3.1 Early Atomic Theories and Origins of Quantum Theory (2)

Atom

The basic unit of a chemical element, containing a nucleus of protons and neutrons, with electrons orbiting around it.

Electron

A negatively charged subatomic particle found in all atoms, orbiting the nucleus.

Proton

A positively charged subatomic particle located in the nucleus of an atom.

Neutron

An electrically neutral subatomic particle found in the nucleus of an atom.

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Mass number (A)

The total number of protons and neutrons in an atom's nucleus.

Atomic number (Z)

The number of protons in an atom's nucleus, which determines the element's identity.

Radioactivity

The spontaneous decay of the nucleus of an atom, often resulting in the emission of radiation.

Photon

A unit of light energy, or a quantum of electromagnetic radiation.

Quantum theory

A framework in physics that describes the behavior of light and matter on very small scales, stating that energy is not continuous but exists in discrete packets.

Scanning tunneling microscope (STM)

A powerful microscope that allows scientists to visualize individual atoms by measuring the tunneling current between a sharp conductive tip and a conductive surface.

Cathode ray tube

An experimental device used by J.J. Thomson to discover the electron, consisting of a vacuum tube with a cathode and anode.

Photoelectric effect

The phenomenon in which electrons are emitted from a material when it absorbs electromagnetic radiation, such as light.

Blueberry muffin model

A model of the atom proposed by J.J. Thomson, in which electrons are embedded in a positively charged 'cloud'.

Rutherford's model of the atom

A model proposing that atoms consist of a dense, positively charged nucleus surrounded by electrons.

Alpha particle

A type of radioactive emission consisting of two protons and two neutrons, equivalent to a helium nucleus.

Beta particle

A type of radioactive emission that consists of high-energy, high-speed electrons or positrons.

Gamma ray

A high-energy electromagnetic radiation emitted by radioactive nuclei.

Electromagnetic spectrum

The range of all types of electromagnetic radiation, including visible light, radio waves, X-rays, and gamma rays.

Max Planck's constant (h)

A fundamental constant in quantum mechanics that relates the energy of a photon to its frequency, approximately 6.63 x 10^-34 J·s.

Democritus

proposed that matter is made up of indivisible particles called "atomos".

Antoine Lavoisier

used experimentation to gather the first accurate quantitative measurements of chemical reactions

J.J Thomson

provide evidence of electron

John Dalton

developed the atomic theory, proposing that all matter is composed of atoms, which cannot be created, destroyed or divided. All atoms in the same element are identical.

Robert Millikan

used charged oil drops to determine the charge of an electron

Mass of a electron

9.11×10^-31kg

Henri Becquerel

in the absence of light, a piece of mineral containing uranium produces an image on a photographic plate. This phenomenon causes uranium atoms spontaneously emit radiation: energy, particles, or waves that travel through space or substances.

Ernest Rutherford

Showed that radioactive resulted from the disintegration of atoms. Also discovered the alpha particle and named the beta particle and gamma ray

discovered the nucleus through gold foil experiment, demonstrating that atoms consist of a dense core surrounded by electrons.

James Chadwick

worked with Rutherford to determine the masses of the nuclei of diff elements

Nucleus only contains positively charged protons and also neutrons