Find the particles in an atom or ion
An atom calculator connects three whole-number labels to the particles they represent. Atomic number, written Z, is the proton count and identifies the element. Mass number, written A, is the total number of protons and neutrons in one isotope. A signed ionic charge records the difference between positive proton charge and negative electron charge. Enter those three values to see the proton, neutron, and electron counts together instead of treating each as an unrelated fact.
The result names the element because the same atomic number cannot belong to two different elements. Changing mass number changes the isotope but not the element. Changing charge changes only the electron count in this calculation. For example, carbon-12 with charge zero contains six protons, six neutrons, and six electrons. A carbon ion with charge 2+ still has the same nucleus but contains four electrons.
The formulas behind the particle counts
Protons equal Z. Neutrons equal A minus Z because the mass number counts both kinds of nucleon. Electrons equal Z minus the signed charge: subtracting a positive charge removes electrons, while subtracting a negative charge adds them. The calculator prints these substitutions so a learner can see why a 1− ion has one more electron than its neutral atom and why a 2+ ion has two fewer.
All three inputs are restricted to whole numbers. A fractional proton, neutron, electron, or mass number is not meaningful in this model. Mass number also cannot be smaller than atomic number because that would imply a negative neutron count. If an entered positive charge would remove more electrons than the atom contains, the page stops and explains the conflict rather than displaying a negative electron count.
How to use atomic number, mass number, and charge
Read isotope notation carefully before typing. In a symbol such as ²³₁₁Na⁺, the lower-left 11 is atomic number, the upper-left 23 is mass number, and the upper-right plus sign is charge. Enter 11, 23, and 1 to obtain 11 protons, 12 neutrons, and 10 electrons. For a charge such as 2−, enter -2; the minus sign matters because it tells the calculator to add two electrons.
Periodic tables usually show a decimal standard atomic weight rather than a single isotope mass number. Do not copy that decimal into the mass-number field. Choose the stated isotope or a whole-number mass number from the problem. If a question gives only an element name and no isotope, the neutron count is not uniquely determined; ask for or select the intended isotope rather than rounding a periodic-table value without explanation.
Check an atom calculator result
First verify that the proton count matches the selected element: hydrogen is 1, carbon is 6, sodium is 11, chlorine is 17, and so on. Next add the displayed protons and neutrons; their sum must reproduce the entered mass number exactly. Finally compare electrons and protons. Equal counts mean neutral, fewer electrons mean a positive ion, and more electrons mean a negative ion.
This three-part check catches common homework errors such as subtracting atomic number from charge, treating charge magnitude as an electron count, or confusing mass number with atomic weight. The visible steps can be copied with the answer, which is useful when a worksheet expects reasoning. Keep the original isotope notation beside the copied result so the signs and left/right positions are not lost.
Scope, privacy, and related chemistry tools
This calculator models protons, neutrons, and electrons for a stated isotope and net charge. It does not calculate nuclear stability, isotope abundance, exact isotope mass, electron binding energy, excited states, or detailed ion electron configurations. Extremely stripped ions may be mathematically countable here even when they are not stable under ordinary conditions, so the result should be read as particle bookkeeping rather than a prediction of laboratory existence.
The values are calculated in the current browser tab. NexaCurrent does not upload the quantities, formulas, chemical names, element choices, or other information entered here, and no account is needed. Copying is a deliberate action after the answer and working are visible. Refreshing or leaving the page clears the current calculation, so keep a copied result if it is needed for later study.