Protons, Neutrons, and Electrons

Three particles. Everything made of matter — every planet, ocean, organism, and grain of dust — is built from combinations of just three particles. Learn their properties, locations, and how their numbers define every element and ion in the universe.

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Q1 Question 1 of 10

Where are protons, neutrons, and electrons located in an atom?

Protons are in the outer shells; neutrons and electrons are in the nucleus All three particles are spread evenly throughout the atom Protons and neutrons are in the central nucleus; electrons occupy the space around the nucleus in shells Electrons are in the nucleus; protons and neutrons orbit outside

Q2 Question 2 of 10

What is the charge of each of the three subatomic particles?

Proton: +2; Neutron: −1; Electron: +1 Proton: +1; Neutron: 0; Electron: −1 Proton: −1; Neutron: 0; Electron: +1 All three particles have the same charge magnitude but in different directions

Q3 Question 3 of 10

What is the atomic number of an element?

The total number of particles (protons + neutrons + electrons) in the atom The number of neutrons in the nucleus The number of protons in the nucleus — this defines which element the atom is The number of electrons in the outermost shell

Q4 Question 4 of 10

What is the mass number of an atom?

The number of electrons in all shells of the atom The total number of protons and neutrons in the nucleus The mass of the atom in grams The number of protons minus the number of neutrons

Q5 Question 5 of 10

An atom has 8 protons and 8 neutrons. What element is it, and what is its mass number?

Nitrogen (atomic number 7); mass number 15 Oxygen (atomic number 8); mass number 16 Carbon (atomic number 6); mass number 14 Neon (atomic number 10); mass number 18

Q6 Question 6 of 10

What are isotopes?

Atoms of the same element with different numbers of electrons Different elements that have the same mass number Atoms of the same element that have the same number of protons but different numbers of neutrons — and therefore different mass numbers Atoms formed when two different elements combine in a fixed ratio

Q7 Question 7 of 10

What is an ion?

An atom that has changed its number of protons through a nuclear reaction A molecule formed when two atoms bond together An atom or group of atoms that has gained or lost electrons, giving it a net electric charge An unstable atom that emits radiation

Q8 Question 8 of 10

A magnesium atom (Mg) loses 2 electrons to form an ion. What is the charge of this ion?

−2 (written as Mg²⁻) +1 (written as Mg⁺) +2 (written as Mg²⁺) 0 — losing electrons does not affect the overall charge

Q9 Question 9 of 10

Why does the mass of an electron not significantly contribute to the atomic mass?

Electrons have no mass — they are pure energy Electrons cancel each other's mass out in pairs An electron's mass is only about 1/1836 of a proton's mass — negligible for atomic mass calculations Electrons are located outside the atom and don't contribute to its mass

Q10 Question 10 of 10

Two atoms: Atom A has 6 protons and 6 neutrons. Atom B has 6 protons and 8 neutrons. Which statement is correct?

They are different elements — Atom B is nitrogen because it has more neutrons Both are carbon atoms (same element), but they are different isotopes — carbon-12 and carbon-14 They are ions of the same element — Atom B has gained 2 extra protons They are the same atom — the number of neutrons doesn't matter

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