Atomic Structure & Ions Flashcards

Vocabulary practice flashcards covering key terms, scientists, experiments, and subatomic concepts from the lecture on Atomic Structure & Ions.

Atom

The smallest particle that makes up an element, consisting of three types of subatomic particles: protons, neutrons, and electrons.

Proton

A positively charged subatomic particle located in the nucleus of an atom with a relative charge of $+1$ and a relative mass of $1$.

Neutron

An uncharged (neutral) subatomic particle located in the nucleus of every atom except simple hydrogen, having approximately the same relative mass as a proton.

Electron

A negatively charged subatomic particle residing outside the nucleus in distinct quantum shells, with a relative charge of $-1$ and a relative mass of approximately $\frac{1}{1840}$.

Democritus

Greek philosopher (460 B.C. – 370 B.C.) who proposed that matter consists of distinct, indivisible, and indestructible particles called "atomos."

John Dalton

Scientist who proposed the Atomic Theory stating that all matter is made of tiny, indivisible, and indestructible particles called atoms, and that atoms of a specific element share identical mass and physical properties.

J.J. Thomson

Scientist who used a cathode ray tube in 1897 to discover the presence of negatively charged subatomic particles called electrons.

Cathode Ray Tube Experiment

An experimental setup where a cathode ray is passed between charged plates and deflected toward the positive plate, demonstrating the existence of negatively charged particles (electrons).

Robert Millikan

Scientist who determined the mass of the electron ($9.11 \times 10^{-28}\,g$, or $\frac{1}{1840}$ the mass of a hydrogen atom) in 1909 using the oil drop apparatus.

Oil Drop Apparatus

An experimental setup using an atomizer, ionizing radiation, charged plates, and a microscope to measure the electric charge and mass of an electron.

Ernest Rutherford

Physicist who discovered the atomic nucleus in 1911 via the gold foil experiment and proved in 1919 that the hydrogen nucleus (officially named proton in 1920) is a fundamental building block inside atomic nuclei.

Gold Foil Experiment

Experiment conducted by Ernest Rutherford starting around 1909 where alpha particles were fired at thin gold foil; most passed straight through, but a few deflected back, demonstrating that an atom has a tiny, dense, positively charged nucleus.

James Chadwick

Physicist who proved the existence of neutrons in 1932 by bombarding beryllium atoms with alpha particles and observing uncharged particles knocking protons out of paraffin wax.

Chadwick's Experiment

An experiment where alpha radiation bombarded a beryllium target, releasing neutral radiation (neutrons) that collided with paraffin wax to eject high-speed protons.

Proton Number (Atomic Number)

The number of protons contained in the nucleus of an atom, represented by the symbol $Z$.

Nucleon Number (Mass Number)

The total combined number of protons and neutrons in the nucleus of an atom, represented by the symbol $A$.

Isotopes

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

Radioisotope

An unstable isotope whose nucleus has an uncomfortable balance of protons and neutrons (or is simply too large) and spontaneously emits high-energy radiation.

Relative Atomic Mass ($A_r$)

The ratio of the average mass of an atom of an element when compared with $\frac{1}{12}\text{th}$ of the mass of a carbon-12 ($^{12}\text{C}$) atom.

Mass Spectrometer

An analytical instrument used to determine the relative atomic mass, relative molecular mass, and isotopic abundance of an element by vaporizing, ionizing, accelerating, deflecting, and detecting ions.

Ion

A charged atom or molecule formed when electrons are added to or removed from a neutral atom.

Cation

A positively charged ion formed when an atom with low electronegativity loses outer-shell electrons, resulting in a total proton count that exceeds the electron count.

Anion

A negatively charged ion formed when an atom with high electronegativity gains additional electrons into its valence shell, resulting in total negative charge exceeding the positive nuclear charge.

Valence Electrons

The electrons located in the outermost shell of an atom that dictate its reactivity, chemical bonding behavior, and group placement in the periodic table.

Americium-241

A radioisotope commonly used in household smoke detectors.

Carbon-14

An unstable radioactive isotope of carbon used in radiocarbon dating.

Technetium-99m

A radioisotope widely used as a medical tracer in diagnostic imaging.

Cobalt-60

A radioisotope used in external beam radiation therapy for cancer treatment and for sterilizing medical equipment safely.

Uranium-235

A radioisotope used as nuclear fuel in nuclear reactors to produce heat energy for electricity generation.