Atom Calculator - Comprehensive Atomic Mass & Number Calculator
An atom calculator is an essential scientific tool that performs various atomic calculations including average atomic mass, atomic number determination, proton-neutron-electron counting, atoms-to-grams conversions, and isotopic abundance analysis. Understanding atomic structure and performing accurate atomic calculations is fundamental to chemistry, physics, nuclear science, materials engineering, and numerous other scientific disciplines. Whether you're calculating the average atomic mass of elements from isotopic data, converting between atoms and grams using Avogadro's number, or determining subatomic particle counts, this comprehensive calculator provides accurate results with detailed step-by-step explanations.
The atomic mass of an element represents the weighted average of all naturally occurring isotopes, calculated by multiplying each isotope's mass by its relative abundance (as a decimal) and summing the results. For example, chlorine has two main isotopes: Cl-35 (75.76% abundance, 34.969 amu) and Cl-37 (24.24% abundance, 36.966 amu), giving an average atomic mass of approximately 35.45 amu. The atomic number equals the number of protons in an atom's nucleus and determines the element's identity—for instance, all carbon atoms have 6 protons regardless of neutron count. Meanwhile, the mass number represents the total count of protons and neutrons. These fundamental concepts interconnect through the relationship: mass number = atomic number + neutron number.
Our comprehensive atom calculator offers seven specialized calculation modes to address diverse scientific needs. You can calculate average atomic mass from isotopic data with multiple isotopes, determine atomic numbers and subatomic particle counts (protons, neutrons, electrons), convert between atoms and grams using molar mass and Avogadro's number (\(6.022 \times 10^{23}\) atoms/mol), perform moles-to-grams conversions, calculate formal charge for molecular structures, determine relative formula mass for compounds, and analyze atomic packing factors for crystalline structures. Each mode provides detailed explanations, showing formulas, substitutions, and step-by-step calculations, making this tool invaluable for chemistry students, research scientists, educators, laboratory technicians, and anyone working with atomic-level calculations in scientific or educational contexts.
Interactive Atom Calculator
Calculate Average Atomic Mass from Isotopes
Calculate Atomic Structure
Convert Between Atoms and Grams
Convert Between Moles and Grams
Calculate Formal Charge
Calculate Relative Formula Mass
Enter each element and its count in the compound. For example, for H₂O enter: H with count 2, O with count 1.
Essential Atomic Formulas
Average Atomic Mass
The average atomic mass is calculated as the weighted average of all naturally occurring isotopes.
Where fractional abundance = percentage abundance ÷ 100. For example: \(35.45 = (34.969 \times 0.7576) + (36.966 \times 0.2424)\)
Atomic Number and Mass Number
The atomic number (Z) equals the number of protons, while the mass number (A) is the sum of protons and neutrons.
For neutral atoms, electrons = protons. For ions: electrons = protons - charge.
Atoms to Grams Conversion
Convert between atoms and grams using Avogadro's number and molar mass.
Avogadro's number (\(N_A = 6.022 \times 10^{23}\)) is the number of particles in one mole.
Moles to Grams Conversion
The relationship between moles and grams uses molar mass as the conversion factor.
Molar mass (g/mol) is numerically equal to atomic mass (amu) for elements.
Formal Charge
Formal charge helps determine the most stable Lewis structure for molecules.
Where V = valence electrons (free atom), N = non-bonding electrons (lone pairs), B = bonding electrons (in bonds). Sum of all formal charges equals the molecular charge.
Relative Formula Mass
The relative formula mass (or molecular weight) is the sum of atomic masses of all atoms in a formula.
Example: H₂O = (2 × 1.008) + (1 × 15.999) = 18.015 amu
Common Elements Reference Table
| Element | Symbol | Atomic Number | Atomic Mass (amu) | Common Isotopes |
|---|---|---|---|---|
| Hydrogen | H | 1 | 1.008 | ¹H, ²H (D), ³H (T) |
| Carbon | C | 6 | 12.011 | ¹²C, ¹³C, ¹⁴C |
| Nitrogen | N | 7 | 14.007 | ¹⁴N, ¹⁵N |
| Oxygen | O | 8 | 15.999 | ¹⁶O, ¹⁷O, ¹⁸O |
| Magnesium | Mg | 12 | 24.305 | ²⁴Mg, ²⁵Mg, ²⁶Mg |
| Chlorine | Cl | 17 | 35.45 | ³⁵Cl, ³⁷Cl |
| Iron | Fe | 26 | 55.845 | ⁵⁴Fe, ⁵⁶Fe, ⁵⁷Fe |
| Copper | Cu | 29 | 63.546 | ⁶³Cu, ⁶⁵Cu |
Key Takeaways
- Average atomic mass = Σ(isotope mass × fractional abundance) - weighted average of all isotopes
- Atomic number (Z) = number of protons, defines the element's identity
- Mass number (A) = protons + neutrons, varies for different isotopes
- For neutral atoms: electrons = protons; for ions: electrons = protons - charge
- Avogadro's number = 6.022 × 10²³ atoms/mol, converts between atoms and moles
- Moles to grams: multiply by molar mass; grams to moles: divide by molar mass
- Formal charge = V - N - B/2, where V=valence, N=non-bonding, B=bonding electrons
- Relative formula mass = sum of (atomic mass × count) for all atoms in formula
- Isotopes have same atomic number but different mass numbers (different neutrons)
- Molar mass (g/mol) numerically equals atomic mass (amu) for elements