The Atom and Nuclear Chemistry

Particles

The general term referring to the substance being measured. Example: atoms, formula units, molecules, ions, etc.

Atom

The smallest unit of an element that has the characteristics of the element.

Element

Composed of one kind of atom and cannot be broken down into simpler substances

Molecules

the smallest particle of a molecular compound. (Note: This is the unit that will be used when a molecular compound's particles are a part of a calculation.)

Compound

two or more different elements chemically combined.

Ionic compound

A compound made from a metal element and a nonmetal element.

Covalent compound

A compound made from 2 nonmetal elements.

pure substance

A material in which all of the particles are identical. Only one type of element or compound is present.

mixture

a physical combination of two or more substances where each component keeps its own chemical identity and properties

proton

stable, positively charges subatomic particle

neutron

subatomic particle with a neutral charge

electron

subatomic particle with a negative charge

nucleus

protons+neutrons; tiny dense center of the atom

atomic number

number of protons in an element

Mass number

number of protons + neutrons in an element

Isotope

different variations of the same element. same number of protons but different numbers of neutrons

atomic mass

the total mass of a single atom of a chemical element, mostly coming from the combined mass of its protons and neutrons

avogadro’s number

6.022×10²³ particles

mole

standard unit of measurement used to express an amount of a substance

formula units

simplest whole-number ratio of ions in an ionic compund

ions

atoms or group of atoms that has an electric charge b/c it has gained or lost electrons

molar mass

mass made of one mole of a substance

molecular mass

total sum of the atomic masses of all atoms in a single molecule.

Plum pudding model

an early 20th-century model of atomic structure proposed by J.J. Thomson, suggesting that negatively charged electrons are embedded within a positively charged 'soup'.

Ruthorford’s nuclear model

describes the atom of mostly empty space with a tiny, dense, positively charged center called the nucleus, where nearly all its mass is packed, while negatively charged electrons spin around it like planets orbiting the sun.

isotope

atoms of the same element w/the same # of protons but different #’s of neutrons.

nucleus

tiny dense region centrally located in the atom that contains all the atoms’s positive charge and nearly all its mass

mass number

represents the number of protons and neutrons in the nucleus of an atom. not given on the periodic table

atomic number

number of protons in an atom

radioactive decay

process in which a radioactive atom spontaneously gives off radiation in the form of energy or particles to reach a more stable state

nuclear radiation (aka ionizing radiation)

the energy released as high-speed charged particles or high-energy electromagnetic waves

nuclear reaction

reaction that shows how one nuclide transmutates into another element via nuclear radiation

transmutation

changing of 1 element into another by radioactive decay

nucleon

either proton or neutron that makes up the center (nucleus) of an atom

alpha particle

positively charged subatomic particle made of 2 protons/2 neutrons

beta particle

high-energy, high-speed electron, or positron emitted from the nucleus of an unstable atom during radioactive decay

gamma ray

high-energy, short wavelength packed of electromagnetic radiation (y) emitted from the nucleus of an atom during radioactive decay

dose

measured quantity of a chemical substance, nutrient or medication absorbed

Background radiation

radiation that is already in the natural world

Half-life

the time required for one-half of a given quantity of a radioactive isotope or reactant substance to undergo decay or change

Decay series

a sequence of steps where an unstable radioactive atom (the parent) transforms through a succession of intermediate atoms (daughters) via radioactive decay until it finally reaches a stable, non-radioactive end-product

Nuclide

a specific type of atom's nucleus that is defined by a precise number of protons and neutrons

Parent nuclide

an unstable radioactive atom that spontaneously transforms into a different nuclide (called a daughter nuclide) through radioactive decay

Daughter nuclide

the new atom or nucleus left behind after an unstable nuclide (called the parent) undergoes radioactive decay

Radioactive nuclide

an atom with an unstable nucleus that spontaneously sheds excess energy by emitting radiation

Transuranium elements

chemical elements with an atomic number greater than 92

Nuclear fusion

a nuclear reaction where two or more light atomic nuclei combine to form a single, heavier nucleus

Chain reaction

a self-sustaining series of chemical events where the products of one reaction fuel the start of the next

Marie Curie (1867 – 1934)

discovering two new elements, polonium and radium, and by proving that radiation comes from inside atoms

Ernest Rutherford (1871 – 1937)

proving that radioactivity involves the spontaneous disintegration of chemical elements

Wilhelm Roentgen (1845 – 1923)

discovery of X-rays

Henri Becquerel (1852 – 1908)

discovering spontaneous radioactivity while investigating uranium salts