{
  "id": "protons-neutrons-electrons",
  "version": "f16889d51afc",
  "status": "published",
  "name": "Protons Neutrons Electrons Calculator",
  "question": "Protons, neutrons and electrons?",
  "summary": "Counts the protons, neutrons and electrons of any atom or ion from its element, mass number and charge: protons = Z, neutrons = A − Z and electrons = Z − charge.",
  "category": "chemistry",
  "subcategory": "atoms",
  "url": "https://www.acalculator.org/chemistry/protons-neutrons-electrons-calculator",
  "markdown": "https://www.acalculator.org/chemistry/protons-neutrons-electrons-calculator.md",
  "kind": "function",
  "method": "Protons = Z (the atomic number); neutrons = A − Z (A is the mass number); electrons = Z − charge. With no mass number typed, A is the mass number of the most abundant isotope in NIST’s table.",
  "assumptions": [
    "The charge is the ion’s whole charge: protons minus electrons.",
    "With no mass number typed, the page uses the isotope with the largest natural abundance in NIST’s isotopic compositions; elements with none (technetium, promethium, polonium to actinium, and elements above uranium) need a typed mass number.",
    "The page does not check that a typed isotope exists or is stable."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "z": {
        "title": "Element",
        "description": "The element, by atomic number, symbol and name; its atomic number Z is its number of protons.",
        "type": "string",
        "enum": [
          "1",
          "2",
          "3",
          "4",
          "5",
          "6",
          "7",
          "8",
          "9",
          "10",
          "11",
          "12",
          "13",
          "14",
          "15",
          "16",
          "17",
          "18",
          "19",
          "20",
          "21",
          "22",
          "23",
          "24",
          "25",
          "26",
          "27",
          "28",
          "29",
          "30",
          "31",
          "32",
          "33",
          "34",
          "35",
          "36",
          "37",
          "38",
          "39",
          "40",
          "41",
          "42",
          "43",
          "44",
          "45",
          "46",
          "47",
          "48",
          "49",
          "50",
          "51",
          "52",
          "53",
          "54",
          "55",
          "56",
          "57",
          "58",
          "59",
          "60",
          "61",
          "62",
          "63",
          "64",
          "65",
          "66",
          "67",
          "68",
          "69",
          "70",
          "71",
          "72",
          "73",
          "74",
          "75",
          "76",
          "77",
          "78",
          "79",
          "80",
          "81",
          "82",
          "83",
          "84",
          "85",
          "86",
          "87",
          "88",
          "89",
          "90",
          "91",
          "92",
          "93",
          "94",
          "95",
          "96",
          "97",
          "98",
          "99",
          "100",
          "101",
          "102",
          "103",
          "104",
          "105",
          "106",
          "107",
          "108",
          "109",
          "110",
          "111",
          "112",
          "113",
          "114",
          "115",
          "116",
          "117",
          "118"
        ]
      },
      "a": {
        "title": "Mass number (A)",
        "description": "Protons plus neutrons in the nucleus, as in carbon-14. Leave it empty for the element’s most abundant isotope.",
        "type": "integer",
        "minimum": 1,
        "maximum": 300
      },
      "q": {
        "title": "Charge",
        "description": "The charge of the ion: 0 for a neutral atom, −1 for an anion such as Cl⁻, +2 for a cation such as Ca²⁺.",
        "type": "integer",
        "minimum": -10,
        "maximum": 118
      }
    }
  },
  "outputs": {
    "result": {
      "label": "Protons, neutrons and electrons",
      "description": "The counts of the three particles, in words.",
      "format": "text"
    },
    "protons": {
      "label": "Protons",
      "description": "Protons in the nucleus: the atomic number Z.",
      "format": "integer"
    },
    "neutrons": {
      "label": "Neutrons",
      "description": "Neutrons in the nucleus: the mass number minus Z.",
      "format": "integer"
    },
    "electrons": {
      "label": "Electrons",
      "description": "Electrons around the nucleus: Z minus the charge.",
      "format": "integer"
    },
    "symbol": {
      "label": "Isotope symbol",
      "description": "The nuclide symbol with the mass number before it and the charge after it, such as ¹²⁷I⁻.",
      "format": "text"
    },
    "isotope": {
      "label": "Isotope",
      "description": "The element name and mass number, such as iodine-127.",
      "format": "text"
    },
    "massNumber": {
      "label": "Mass number (A)",
      "description": "The mass number used.",
      "format": "integer"
    },
    "basis": {
      "label": "Mass number from",
      "description": "Whether the mass number was typed or is the most abundant natural isotope in NIST’s table.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "z": "53",
      "q": 0
    },
    "outputs": {
      "result": "53 protons, 74 neutrons and 53 electrons",
      "protons": 53,
      "neutrons": 74,
      "electrons": 53,
      "symbol": "¹²⁷I",
      "isotope": "iodine-127",
      "massNumber": 127,
      "basis": "The most abundant natural isotope (NIST)"
    },
    "text": "¹²⁷I has 53 protons, 74 neutrons and 53 electrons."
  },
  "examples": [
    {
      "given": {
        "z": "53",
        "a": 127,
        "q": -1
      },
      "expect": {
        "protons": 53,
        "neutrons": 74,
        "electrons": 54,
        "symbol": "¹²⁷I⁻"
      },
      "source": "OpenStax, Chemistry 2e, §2.3 Atomic Structure and Symbolism (A = Z + neutrons; charge = protons − electrons), https://openstax.org/books/chemistry-2e/pages/2-3-atomic-structure-and-symbolism, Example 2.3 Composition of an Atom: 53 protons, 74 neutrons and 54 electrons"
    },
    {
      "given": {
        "z": "78",
        "a": 195,
        "q": 4
      },
      "expect": {
        "protons": 78,
        "neutrons": 117,
        "electrons": 74,
        "symbol": "¹⁹⁵Pt⁴⁺"
      },
      "source": "OpenStax, Chemistry 2e, §2.3 Atomic Structure and Symbolism (A = Z + neutrons; charge = protons − electrons), https://openstax.org/books/chemistry-2e/pages/2-3-atomic-structure-and-symbolism, Check Your Learning after Example 2.3: 78 protons, 117 neutrons, charge 4+"
    },
    {
      "given": {
        "z": "6",
        "q": 0
      },
      "expect": {
        "massNumber": 12,
        "neutrons": 6,
        "electrons": 6,
        "isotope": "carbon-12"
      },
      "source": "NIST, Atomic Weights and Isotopic Compositions for All Elements, https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=&ascii=html&isotype=some: carbon-12 has the largest isotopic composition, 0.9893; hand calculation in content.mdx"
    },
    {
      "given": {
        "z": "17",
        "q": -1
      },
      "expect": {
        "massNumber": 35,
        "neutrons": 18,
        "electrons": 18,
        "symbol": "³⁵Cl⁻"
      },
      "source": "NIST, Atomic Weights and Isotopic Compositions for All Elements, https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=&ascii=html&isotype=some: chlorine-35, 0.7576; hand calculation in content.mdx: 35 − 17 = 18 neutrons, 17 + 1 = 18 electrons"
    },
    {
      "given": {
        "z": "92",
        "a": 235,
        "q": 0
      },
      "expect": {
        "neutrons": 143,
        "electrons": 92,
        "result": "92 protons, 143 neutrons and 92 electrons"
      },
      "source": "OpenStax, Chemistry 2e, §2.3 Atomic Structure and Symbolism (A = Z + neutrons; charge = protons − electrons), https://openstax.org/books/chemistry-2e/pages/2-3-atomic-structure-and-symbolism (neutrons = A − Z); hand calculation in content.mdx: 235 − 92 = 143"
    }
  ],
  "sources": [
    "OpenStax, Chemistry 2e, §2.3 Atomic Structure and Symbolism: atomic number Z, mass number A = Z + neutrons, charge = protons − electrons, Example 2.3 (iodine-127 anion: 53 protons, 74 neutrons, 54 electrons) and its Check Your Learning (platinum-195 with 74 electrons: charge 4+). https://openstax.org/books/chemistry-2e/pages/2-3-atomic-structure-and-symbolism (retrieved 2026-10-19)",
    "NIST, Atomic Weights and Isotopic Compositions for All Elements: the isotopic composition of every isotope; the page uses the mass number of the largest one. https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=&ascii=html&isotype=some (retrieved 2026-10-19)",
    "CIAAW (IUPAC Commission on Isotopic Abundances and Atomic Weights), Standard Atomic Weights: element names and symbols for Z = 1 to 118. https://www.ciaaw.org/atomic-weights.htm (retrieved 2026-10-19)"
  ],
  "related": [
    "atomic-mass",
    "electron-configuration",
    "valence-electrons",
    "half-life"
  ],
  "changelog": []
}