3 Atomic Structure (Video) - Vocabulary Flashcards

A set of vocabulary-style flashcards covering key terms and concepts from the lecture notes on atomic structure and related topics.

Atom

The basic unit of matter that retains the properties of an element, composed of protons, neutrons, and electrons.

Element

A substance made of only one kind of atom.

Compound

A substance formed when two or more elements are chemically bound in fixed proportions.

Percent Composition

The mass percentage of each element present in a compound.

Law of Conservation of Mass

Mass is neither created nor destroyed during ordinary chemical reactions or physical changes.

Law of Definite Proportions

A chemical compound contains its elements in exact fixed proportions by mass.

Law of Multiple Proportions

If two elements form more than one compound, the mass ratio of the second element is a ratio of small whole numbers.

Proton

Positively charged subatomic particle in the nucleus; defines the atomic number Z; mass ≈ 1 amu.

Neutron

Electrically neutral subatomic particle in the nucleus; adds mass without changing charge.

Electron

Negatively charged subatomic particle surrounding the nucleus; participates in bonding; mass ≈ 9.11×10⁻³¹ kg.

Nucleus

Dense center of the atom containing protons and neutrons.

Electron Cloud

Region around the nucleus where electrons are likely to be found, in orbitals.

Atomic Number (Z)

Number of protons in the nucleus; defines the element; in a neutral atom equals the number of electrons.

Mass Number (A)

Total number of protons and neutrons in the nucleus.

Isotope

Atoms of the same element (same Z) with different numbers of neutrons, hence different A.

Ion

An atom with a net electric charge due to loss or gain of electrons.

Cation

Positively charged ion that has lost electrons.

Anion

Negatively charged ion that has gained electrons.

Quarks

Fundamental constituents of protons and neutrons; held together by gluons.

Up quark

+2/3 elementary charge; one of the quark types in protons and neutrons.

Down quark

-1/3 elementary charge; one of the quark types in protons and neutrons.

Proton composition

Proton is made of two up quarks and one down quark (2u + 1d) giving a +1 charge.

Neutron composition

Neutron is made of one up quark and two down quarks (1u + 2d) giving a neutral charge.

Energy Level (n)

Principal quantum number; indicates the shell where electrons reside (n=1,2,3,… ).

Sublevel

Divisions within an energy level named s, p, d, and f.

Orbital

A region within a sublevel where an electron is likely to be found; holds up to 2 electrons.

Max electrons per shell

The maximum number of electrons in shell n is 2n².

Aufbau Principle

Electrons fill the lowest-energy orbitals first before higher ones.

Pauli Exclusion Principle

An orbital holds at most two electrons with opposite spins.

Hund's Rule

Electrons occupy degenerate orbitals singly before pairing in the same orbital.

Noble Gas Notation

A shorthand electron configuration using the nearest noble gas in brackets followed by outer electrons.

Valence Electrons

Electrons in the outermost shell that determine chemical reactivity and bonding.

Electron Configuration Notation

Notation showing the distribution of electrons among the orbitals (e.g., 1s² 2s² 2p⁴).

Orbital Notation

Diagrams showing electrons as arrows within orbital boxes to indicate spin.

Bohr Model

Early model where electrons orbit the nucleus in fixed energy levels.

Photon

Quantum of light emitted when an electron drops to a lower energy level.

Strong Nuclear Force

Force that binds protons and neutrons in the nucleus, overcoming repulsion.

Electromagnetic Force

Force that attracts electrons to the positively charged nucleus; governs bonding.

Weak Nuclear Force

Force responsible for radioactive decay processes.

Rutherford Gold Foil Experiment

Geiger–Marsden experiment showing deflected alpha particles, revealing a dense nucleus.

Isotope (examples)

Atoms of the same element with different neutron numbers, e.g., Carbon-12, Carbon-13, Carbon-14.

Radiocarbon dating

Dating method using Carbon-14 to determine age of ancient organic remains.

Medical Isotopes

Isotopes used in medicine, e.g., Iodine-131 and Technetium-99m for imaging/treatment.