Atomic structure refers to the arrangement of subatomic particles within an atom, including electrons, protons, and neutrons. Electrons, negatively charged particles, orbit the nucleus, which contains positively charged protons and neutral neutrons. Understanding atomic structure is essential for grasping how elements interact, form bonds, and create compounds, forming the basis of chemistry and matter’s behavior.
Which subatomic particle has a negative charge? (a) Proton (b) Electron (c) Neutron (d) Positron
Who discovered the electron using cathode ray tubes? (a) Ernest Rutherford (b) J.J. Thomson (c) James Chadwick (d) Niels Bohr
The neutron’s mass is approximately equal to the mass of a: (a) Proton (b) Electron (c) Positron (d) Photon
Which subatomic particle determines the atomic number? (a) Neutron (b) Electron (c) Proton (d) All subatomic particles
Protons are found in the atom’s: (a) Electron cloud (b) Orbitals (c) Outer shell (d) Nucleus
The relative charge on a proton is: (a) -1 (b) 0 (c) +1 (d) +2
Most of an atom’s volume is occupied by its: (a) Nucleus (b) Protons (c) Electrons (d) Neutrons
Which statement is true about neutrons? (a) They carry a +1 charge (b) They are found only in ions (c) They are slightly more massive than protons (d) They orbit in shells
The subatomic particle with the smallest mass is: (a) Proton (b) Neutron (c) Electron (d) All have the same mass
Which scientist confirmed the existence of the neutron? (a) James Chadwick (b) Robert Millikan (c) John Dalton (d) Max Planck
Carbon-14 differs from carbon-12 in the number of: (a) Electrons (b) Protons (c) Neutrons (d) Positrons
The approximate mass of a proton is: (a) 1 amu (b) 0.00055 amu (c) 2 amu (d) 1 × 10-28 g
In a neutral atom, the number of protons equals the number of: (a) Neutrons (b) Electrons (c) Quarks (d) Nucleons
Which subatomic particle was discovered first? (a) Proton (b) Neutron (c) Electron (d) They were discovered at the same time
Which particles reside in the nucleus? (a) Protons and electrons (b) Electrons and neutrons (c) Protons and neutrons (d) Only neutrons
An atom’s identity is defined by its: (a) Number of electrons (b) Number of protons (c) Total number of nucleons (d) Neutron-proton ratio
An atom with 8 protons, 8 electrons, and 10 neutrons has a mass number of: (a) 8 (b) 10 (c) 16 (d) 18
“Nucleons” refers to: (a) Protons, neutrons, and electrons (b) Only neutrons (c) Electrons and neutrons (d) Protons and neutrons
Millikan’s oil drop experiment measured the charge of the: (a) Proton (b) Neutron (c) Electron (d) Alpha particle
An ion differs from a neutral atom by its number of: (a) Protons (b) Electrons (c) Neutrons (d) All subatomic particles
Which subatomic particle determines the chemical behavior of an atom most directly? (a) Proton (b) Neutron (c) Electron (d) All are equally responsible
If an atom has 9 protons, 10 neutrons, and 9 electrons, its mass number is: (a) 9 (b) 18 (c) 19 (d) 28
In Rutherford’s gold foil experiment, most alpha particles passed straight through because: (a) Alpha particles are massless (b) The nucleus is very small and atoms are mostly empty space (c) Gold atoms have no electrons (d) Alpha particles have a negative charge
Which of these subatomic particles are located outside the nucleus? (a) Protons (b) Neutrons (c) Electrons (d) Protons and neutrons
Isotopes of the same element must have the same number of: (a) Protons (b) Neutrons (c) Mass numbers (d) Electrons + Neutrons
All atoms of a given element have the same: (a) Atomic mass (b) Mass number (c) Number of protons (d) Number of neutrons
When an atom gains or loses electrons, it becomes a(n): (a) Isotope (b) Molecule (c) Ion (d) New element
If a neutral atom of sodium (Na) loses 1 electron, it will have a: (a) -1 charge (b) +1 charge (c) -2 charge (d) +2 charge
Relative mass of electron vs. proton is about: (a) They have the same mass (b) Electron is ~1,800 times lighter (c) Electron is ~2 times heavier (d) Proton is 10 times lighter
Answer Key
(b) Electron has a negative charge.
(b) J.J. Thomson used cathode ray tubes.
(a) Neutron ~ same mass as proton.
(c) Proton count = atomic number.
(d) Protons are in the nucleus.
(c) Proton’s charge is +1.
(c) Electrons occupy most of the atom’s volume.
(c) Neutrons are slightly more massive than protons, no charge.
(c) Electron is the lightest subatomic particle listed.
(a) James Chadwick discovered the neutron (1932).
(c) Carbon-14 has more neutrons than carbon-12.
(a) Proton’s mass ~1 amu.
(b) Neutral atom: protons = electrons.
(c) Electron was discovered first (1897). Proton (1911), neutron (1932).
(c) Protons + neutrons = nucleus.
(b) Number of protons defines the element.
(d) 8p + 10n = mass number 18.
(d) Nucleons = protons + neutrons.
(c) Millikan measured the electron’s charge.
(b) Ion forms by losing/gaining electrons.
(c) Electrons mainly determine chemical behavior.
(c) 9 protons + 10 neutrons = 19 mass number.
(b) Nucleus is tiny; atoms mostly empty space.
(c) Electrons lie outside the nucleus.
(a) Isotopes share the same proton count.
(c) They share the same atomic number (protons). Neutrons may vary.
(a) Beta (β–) = high-speed electrons from nuclear decay.
(c) Gaining or losing electrons → ion.
(b) Losing 1 electron → +1 ion (cation).
(b) Electron is ~1/1836 of proton’s mass (~1,800 times lighter).