Explore atomic structure: find protons, neutrons, electrons, mass number, and isotope notation for any element. Includes ion charges, isotope data, and periodic table reference.
Atoms are the fundamental building blocks of matter, composed of protons, neutrons, and electrons. The atomic number (Z) defines the element and equals the number of protons in the nucleus. The mass number (A) is the total of protons and neutrons. Electrons orbit the nucleus and determine chemical behavior — in a neutral atom, the number of electrons equals the number of protons.
Understanding atomic structure is essential for all of chemistry. The number of protons determines the element's identity, the number of neutrons defines the isotope, and the electron configuration governs chemical bonding and reactivity. Ions form when atoms gain or lose electrons, changing the net charge while keeping the same nucleus.
This calculator lets you look up any element by name, symbol, or atomic number and instantly see its subatomic particle counts, isotope notation, common ions, and key properties. You can adjust the mass number to explore different isotopes and modify the charge to see how ions form. It serves as a comprehensive atomic structure reference tool.
Quickly determine the subatomic structure of any element, including ions and specific isotopes. This is essential for chemistry students learning atomic theory, nuclear chemistry, and electron configuration. This atom calculator helps you compare outcomes quickly and reduce avoidable mistakes when making day-to-day care decisions. Use the estimate as a planning baseline and confirm final decisions with a qualified professional when risk is high.
Atomic Number (Z) = number of protons = number of electrons (neutral atom) Mass Number (A) = protons + neutrons Neutrons (N) = A - Z Electrons in ion = Z - charge Isotope notation: ᴬ_Z X (e.g., ¹²₆C)
Result: Fe³⁺: 26p, 30n, 23e⁻
Iron (Fe) has atomic number 26, so 26 protons. With mass number 56: neutrons = 56 - 26 = 30. As Fe³⁺ (lost 3 electrons): electrons = 26 - 3 = 23. The nuclear notation is ⁵⁶₂₆Fe³⁺.
The atom consists of a dense nucleus containing protons (positive charge, mass ≈ 1 amu) and neutrons (neutral, mass ≈ 1 amu), surrounded by electrons (negative charge, mass ≈ 1/1836 amu). The nucleus is incredibly small — about 10⁻¹⁵ m compared to the atom's 10⁻¹⁰ m — yet contains over 99.9% of the atom's mass.
Not all combinations of protons and neutrons are stable. The band of stability shows which isotopes are stable versus radioactive. Light elements (Z < 20) tend to have N ≈ Z. Heavier elements require proportionally more neutrons for stability. Elements with even numbers of protons and/or neutrons tend to be more stable due to nuclear shell effects.
Isotopes have numerous practical applications: ¹⁴C dating in archaeology, ¹³¹I in thyroid treatment, ²³⁵U in nuclear power, ²H (deuterium) in NMR spectroscopy, and ¹⁸O in metabolic tracer studies. Stable isotope ratios are used in geochemistry, forensics, and food authentication.
The number of protons (atomic number Z) uniquely identifies the element. Changing the number of protons changes the element entirely (nuclear transmutation).
Isotopes are atoms of the same element (same Z) with different numbers of neutrons (different A). For example, ¹²C, ¹³C, and ¹⁴C are all carbon isotopes.
Ions form when atoms gain or lose electrons. Metals typically lose electrons to form cations (positive charge). Nonmetals typically gain electrons to form anions (negative charge).
The strong nuclear force, which acts over very short distances, overcomes the electrostatic repulsion between protons. Neutrons help stabilize the nucleus by providing additional strong force without adding repulsion.
Each element has a most abundant isotope. For example, ¹H (99.98%), ¹²C (98.9%), ¹⁶O (99.76%), ⁵⁶Fe (91.7%). The standard atomic mass is a weighted average of all isotopes.
The standard atomic mass on the periodic table is a weighted average of all naturally occurring isotopes, so it is rarely a whole number. Only pure isotopes have integer mass numbers.