Atomic Structure and Discoveries

Thomson's model of the atom, where negatively charged electrons are embedded in a positively charged sphere like plums in a pudding.

J.J. Thomson used a cathode ray tube to demonstrate the existence of electrons. He observed that a beam of particles, later identified as electrons, traveled from the cathode to the anode.

Robert Millikan's experiment involved observing the motion of tiny oil drops suspended between charged plates. By analyzing how the drops moved, he could determine the charge of a single electron.

The positively charged particle found in the nucleus of an atom. Ernest Rutherford discovered the proton through his gold foil experiment.

Ernest Rutherford's experiment involved firing alpha particles (positively charged) at a thin gold foil. He observed that most particles passed through, while some were deflected or even bounced back, revealing the existence of a small, dense, positively charged nucleus in the atom.

Matter is made up of tiny, indestructible particles called atoms. Each element has unique atoms.

Atoms of a given element are identical. Atoms of different elements are different.

Compounds form when atoms of different elements combine in specific ratios.

Chemical reactions only rearrange atoms, not changing the atoms themselves.

Atoms are the smallest particles of matter and cannot be divided further.

When two elements combine to form multiple compounds, the mass ratios of one element to the other element are in simple whole-number ratios.

A specific chemical compound always has the same elements present by mass.

Dalton's theory was later proved incorrect. Atoms are divisible into smaller particles like protons, neutrons, and electrons.

A model of the atom where negatively charged electrons orbit a positively charged nucleus, similar to the planets orbiting the Sun.

An experiment where alpha particles were directed at a thin gold foil. Most passed through, some deflected, and a few bounced back.

The concentrated positive charge in an atom, composed of protons and neutrons.

Protons and neutrons are found in the nucleus of an atom.

A variant of an element that has the same number of protons but a different number of neutrons.

An atom that has gained or lost electrons, resulting in a net positive or negative charge.

The number of protons in an atom's nucleus.

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

The number of neutrons in an atom's nucleus.

The standard atomic mass of an element, rounded to the nearest whole number.

The weighted average of the masses of all isotopes of an element, taking into account their relative abundances.

The most abundant isotope of an element is usually the one closest to the average atomic mass.

A rule that helps determine the direction of a magnetic field generated by a moving charge.

The process of objectively establishing facts through experimentation and testing.

A negatively charged particle that orbits the nucleus of an atom.

Red light has the lowest energy level, while purple light has the highest.

The distance between two consecutive wave crests or troughs.

The energy of light waves is inversely proportional to the wavelength; shorter wavelengths have higher energy, and longer wavelengths have lower energy.

A technique that uses the interaction of light with matter to identify and analyze substances.

Spectral lines on a black background, representing the specific wavelengths of light emitted by an excited atom or molecule.

Dark lines on a continuous spectrum, showing the wavelengths of light absorbed by a substance.

A pattern of alternating bright and dark bands formed when light waves interfere; it provides evidence for the wave nature of light.

The phenomenon where electrons are ejected from a metal surface when light shines on it; it provides evidence for the particle nature of light.

A model of the atom developed by Neils Bohr, where electrons orbit the nucleus in specific energy levels.

The hypothesis stating that electrons can exhibit wave-like behavior.

A model of the atom based on quantum mechanics, where electrons are described by wave function and exist in orbitals.

The principle stating that it is impossible to simultaneously determine both the position and momentum of an electron with perfect accuracy.

A method of representing the arrangement of electrons in an atom using symbols for the subshells (s, p, d, f) and their respective numbers of electrons.

A rule stating that electrons fill orbitals in order of increasing energy level.

A rule stating that electrons occupy orbitals individually before pairing up in the same orbital.

A law stating that chemical properties of elements repeat every eight elements.

The electrons located on the outermost electron shell of an atom.

The repulsion between inner electron shells that reduces the attraction between the nucleus and outer electrons.

The number of protons in an atom's nucleus.

The force of repulsion between electrons in an atom, which increases as the number of electrons increases.

A measure of an atom's ability to attract shared electrons in a chemical bond.

The energy required to remove an electron from an atom or ion.

The distance from the nucleus to the outermost electron shell in an atom or ion.

Strong bonds formed when electrons are shared between atoms, providing high melting and boiling points.

Bonds formed between a metal and a nonmetal, where electrons are transferred from the metal to the nonmetal.

Bonds formed between two nonmetals by sharing electrons, resulting in either nonpolar or polar covalent bonds.

A visual representation of the valence electrons in an atom or molecule, used to predict chemical bonding.

A method for predicting the shape of molecules based on the repulsion of electron pairs around the central atom.

The mixing of atomic orbitals to form hybrid orbitals, which explain the shape and bonding of molecules.

A concept where atoms can have more than eight valence electrons, especially in the d and f blocks, allowing for more bonds.