Getting your questions ready
Getting your questions ready
Beat the crowd
10 questions No timer
50 free Atomic Structure trivia questions with answers — science & nature quiz, new questions added Aug 2026.
Everything you can touch is made of atoms, and almost all of every atom is empty space: a speck of a nucleus surrounded by electrons that behave less like planets and more like a haze of probability. Working out that picture took a century of arguments, and most of the names on the way are half-remembered from a school lab. These 50 questions follow the story in order: the Greek idea of an indivisible particle, the chemists who made atoms measurable, the cathode-ray tubes that exposed the first subatomic particle, the gold-foil scattering that found the nucleus, and the quantum models of the 1920s that gave us shells and orbitals. Along the way come isotopes and ions, mass number and atomic number, and the people, some famous and some forgotten, who named the pieces. It suits anyone revising for a chemistry or physics exam, a pub-quiz science round, or a reader who wants to know why the periodic table is shaped the way it is. Every answer carries a short explanation that adds one fact the textbook left out.
30 of 50 questions with answers and explanations. Play the quiz
Q 01The word 'atom' comes from the ancient Greek 'atomos', which described matter as being what?
Uncuttable
Uncuttable is what 'atomos' meant, an idea so old that it appeared in several ancient cultures long before anyone could test it.
Q 02By roughly what factor does a proton outweigh an electron, leaving the nucleus with nearly all an atom's mass?
1,836
1,836 to one is the proton-to-electron mass ratio, yet the two particles carry exactly equal and opposite charges.
Q 03Which radioactive isotope with a 12-year half-life makes exit signs and watch hands glow with no power source?
Tritium
Tritium is hydrogen with two neutrons, its name from the Greek 'tritos', meaning 'third'; its half-life is 12.32 years.
Q 04A neutron pulled out of a nucleus is unstable; what is a free neutron's mean lifetime before decaying into a proton?
About 15 minutes
About 15 minutes on average, leaving a proton, an electron and an antineutrino; the neutron is itself slightly heavier than the proton it becomes.
Q 05The name for the atom's dense centre, adopted by Rutherford in 1912, is a Latin diminutive of the word for what?
Nut
Nut is nux in Latin, and 'nucleus' is its diminutive, the 'little nut' inside a fleshy fruit; Rutherford borrowed the word for the atom's core.
Q 06The rule that electrons fill the lowest-energy subshells first is named from the German word for what?
Building up
Building up is what 'Aufbau' means, and the same building-up idea applied to protons and neutrons gives the nuclear shell model.
Q 07J. J. Thomson's Nobel Prize showed the electron is a particle; his son George's Nobel showed it is also what?
A wave
A wave is what George Paget Thomson saw electrons behave as, diffracting through crystals, for which he shared the 1937 Nobel with Clinton Davisson.
Q 08Which English chemist's 'A New System of Chemical Philosophy' held that all atoms of one element are identical?
John Dalton
John Dalton was colour-blind and gave the condition its first scientific description, which is why several languages still call it Daltonism.
Q 09A hydrogen atom's radius is roughly how many times that of its nucleus, a lone proton?
60,000
60,000 to one: a proton is only about 1.7 femtometres across, while hydrogen's atom has a radius of some 53 picometres; uranium's ratio is a mere 27,000.
Q 10An atom that loses electrons becomes which kind of ion, its name taken from the Greek for 'down'?
Cation
A cation has fewer electrons than protons, so it is positive and moves toward the cathode; its opposite, the anion, is named from the Greek for 'up'.
Q 11In the isotope label cobalt-60, what does the number 60 count?
Protons plus neutrons
Protons plus neutrons together, the nucleons, make up the mass number, whose symbol A comes from the German Atomgewicht, 'atomic weight'.
Q 12Which isotope did Harold Urey find in 1931 by distilling five litres of liquid hydrogen down to a single millilitre?
Deuterium
Deuterium, hydrogen with one neutron, gives heavy water its extra mass; the name is from the Greek 'deuteros', 'second', and the find earned Urey the 1934 Nobel Prize in Chemistry.
Q 13Unlike the proton, the electron has no known inner parts, so physicists class it as what kind of particle?
Elementary
Q 21Borrowed from X-ray notation, the label for the electron shell nearest the nucleus is which letter?
K
K is followed outward by L, M, N, O, P and Q; Charles Barkla, whose X-ray scattering work supplied the letters, had originally called his two X-ray types 'A' and 'B'.
Q 22Which quantum number, written n, fixes an electron's shell and therefore most of its energy?
Principal
The principal quantum number describes the electron shell; the shells counted outward from the nucleus are simply n = 1, 2, 3 and so on.
Q 23The symbol Z for an element's proton count comes from which German word, meaning 'number'?
Zahl
Zahl once denoted only an element's numerical place in the periodic table, an order that matched atomic weight only approximately.
Elementary particles have no known components or substructure; the electron sits in the first generation of the Standard Model's matter particles.
Q 14How many electrons at most can occupy an atom's third shell, the first one to add d orbitals to s and p?
18
18 is 2 + 6 + 10 from the s, p and d subshells, matching the general rule that the nth shell holds up to 2n² electrons.
Q 15Whose wave equation of January 1926 replaced Bohr's electron orbits with the probability clouds now called orbitals?
Erwin Schrödinger
Erwin Schrödinger's equation yields the wave function of a system and how it changes in time; the paper appeared in Annalen der Physik.
Q 16The word 'isotope', coined in 1913, is built from two Greek roots that together mean what?
Same place
Same place is 'isos' plus 'topos': isotopes of an element share one square of the periodic table despite their different masses.
Q 17The electron belongs to which family of particles, ones that never feel the strong force binding the nucleus?
Leptons
Leptons include the electron plus its heavier copies, the muon and the tau, which match it in charge, spin and interactions but weigh far more.
Q 18Which metal, familiar from cans and solder, has ten stable isotopes, more than any other element?
Tin
Tin holds the record with ten; about two-thirds of the stable elements occur in nature as a blend of several stable isotopes.
Q 19What name did J. J. Thomson give the particles he found in cathode rays in 1897, before 'electron' won out?
Corpuscles
Corpuscles, Thomson found, were more than 1,000 times lighter than a hydrogen atom and identical whichever gas they came from.
Q 20The orbital letters s, p, d and f came from old spectroscopy jargon; what does the 's' stand for?
Sharp
Sharp came with three siblings describing series of alkali-metal spectral lines, 'diffuse' and 'fundamental' for d and f among them, long before anyone had pictured an orbital.
Q 24The unified atomic mass unit is defined as one twelfth of the mass of a single unbound atom of which isotope?
Carbon-12
Carbon-12 at rest in its ground state sets the scale: one twelfth of its mass is exactly 1 Da, and the definition survived the 2019 SI revision.
Q 25Chadwick's 1932 discovery came from firing polonium's alpha particles at a target of which light metal?
Beryllium
Beryllium under alpha bombardment gives off neutral radiation that the Joliot-Curies had taken for gamma rays; Chadwick showed it was a neutral particle with nearly a proton's mass.
Q 26A proton is built from three quarks bound by gluons; which combination of flavours does it contain?
Two up, one down
Two up, one down adds up: up quarks carry +2/3 each and the down quark −1/3, giving the proton its charge of exactly +1.
Q 27Which American chemist's 1916 paper introduced the shared electron pair and the 'rule of eight'?
Gilbert N. Lewis
Gilbert N. Lewis had sketched 'cubical atoms' in lecture notes since about 1902, with electrons at the corners, and Lewis dot diagrams still carry his name.
Q 28Which German physicist's rule has electrons fill a subshell's orbitals singly, with parallel spins, before any pair up?
Friedrich Hund
Friedrich Hund's rule of maximum multiplicity is one of several rules bearing his name, and in 1926 he also discovered quantum tunnelling.
Q 29What is the name for the most probable nucleus-to-electron distance, about 53 picometres, in ground-state hydrogen?
Bohr radius
The Bohr radius is 5.29×10⁻¹¹ m; in Bohr's 1913 model the electron orbited at almost exactly that distance, and quantum mechanics later made it merely the likeliest.
Q 30Which Cambridge polymath, who also coined the word 'scientist', suggested the term 'ion' to Michael Faraday?
William Whewell
William Whewell also supplied Faraday with 'electrode', 'anode', 'cathode' and 'dielectric', and coined 'physicist' and 'linguistics' besides.