Exact Molecular Weight Calculator
Accurately determine the molecular weight of chemical compounds.
Enter the chemical formula using standard element symbols and subscripts. Example: H2O for water, C6H12O6 for glucose.
Calculated Molecular Weight
0.00
g/mol
Molecular Weight = Σ (Number of Atoms of Element × Atomic Weight of Element)
Total Atoms
0
atoms
Unique Elements
0
elements
Atomic Weight Sum
0.00
g/mol
What is Exact Molecular Weight?
The exact molecular weight, also known as the molar mass, is a fundamental property of a chemical compound. It represents the mass of one mole of that substance, expressed in grams per mole (g/mol). This value is crucial for stoichiometric calculations in chemistry, allowing scientists to determine the quantitative relationships between reactants and products in chemical reactions. Understanding the exact molecular weight helps in identifying substances, verifying purity, and designing experiments effectively.
This exact molecular weight calculator is designed for students, researchers, chemists, and anyone working with chemical compounds who needs a quick and accurate determination of this critical value. It simplifies the process of summing up the atomic weights of all atoms within a molecule's chemical formula.
A common misconception is that molecular weight is a fixed, unchanging property. While the *standard* atomic weights are well-defined, the term "exact" emphasizes precision. For most practical purposes, using standard atomic weights is sufficient. However, for highly precise scientific work, isotopic variations can lead to slight differences, although this calculator primarily uses standard atomic weights. Another misconception is confusing molecular weight with atomic weight; molecular weight applies to compounds (molecules), while atomic weight applies to individual elements.
Molecular Weight Formula and Mathematical Explanation
The calculation of the exact molecular weight for a given chemical compound is straightforward, involving the summation of the atomic weights of all constituent atoms within the molecule. The general formula is:
Molecular Weight (M) = Σ (Number of Atoms of Element × Atomic Weight of Element)
Let's break down the formula:
- Σ (Sigma Notation): This symbol indicates summation. We are adding up values for each element in the compound.
- Number of Atoms of Element: This is the count of a specific element's atoms as indicated by the subscript in the chemical formula. If no subscript is present, it's assumed to be 1.
- Atomic Weight of Element: This is the average mass of atoms of an element, calculated using the relative abundance of isotopes. Standard atomic weights are typically used and are found on the periodic table.
Step-by-Step Derivation:
- Identify Elements: Parse the chemical formula to identify all unique elements present.
- Count Atoms: For each element, determine the number of atoms present in the molecule, as indicated by the subscripts in the formula.
- Find Atomic Weights: Look up the standard atomic weight for each identified element from a reliable periodic table.
- Calculate for Each Element: Multiply the count of atoms for each element by its respective atomic weight.
- Sum Results: Add the results from step 4 for all elements together to obtain the total molecular weight of the compound.
Variables Table:
| Variable | Meaning | Unit | Typical Range/Source |
|---|---|---|---|
| Chemical Formula | Representation of the elements and their counts in a molecule | N/A | e.g., H₂O, C₆H₁₂O₆ |
| Element Symbol | Abbreviation for a chemical element | N/A | e.g., H, O, C, Na, Cl |
| Subscript (Atom Count) | Number of atoms of a specific element in the molecule | Count | Integer ≥ 1 |
| Atomic Weight | Average mass of atoms of an element | g/mol (or amu) | Periodic Table values (e.g., H ≈ 1.008, O ≈ 15.999, C ≈ 12.011) |
| Molecular Weight (M) | Total mass of one mole of the compound | g/mol | Calculated value, depends on the compound |
Practical Examples (Real-World Use Cases)
Let's illustrate the calculation of exact molecular weight with a couple of common examples:
Example 1: Water (H₂O)
Inputs:
- Chemical Formula: H2O
Calculation Steps:
- Elements identified: Hydrogen (H), Oxygen (O).
- Atom counts: H = 2, O = 1.
- Atomic Weights (approximate standard values): H ≈ 1.008 g/mol, O ≈ 15.999 g/mol.
- Calculations per element:
- Hydrogen: 2 atoms × 1.008 g/mol = 2.016 g/mol
- Oxygen: 1 atom × 15.999 g/mol = 15.999 g/mol
- Summation: 2.016 g/mol + 15.999 g/mol = 18.015 g/mol
Outputs:
- Molecular Weight: 18.015 g/mol
- Total Atoms: 3
- Unique Elements: 2
- Atomic Weight Sum: 18.015 g/mol
Interpretation: This means that one mole (approximately 6.022 x 10²³ molecules) of water weighs 18.015 grams. This value is fundamental for calculating concentrations in solutions or determining reactant quantities in chemical synthesis involving water.
Example 2: Glucose (C₆H₁₂O₆)
Inputs:
- Chemical Formula: C6H12O6
Calculation Steps:
- Elements identified: Carbon (C), Hydrogen (H), Oxygen (O).
- Atom counts: C = 6, H = 12, O = 6.
- Atomic Weights (approximate standard values): C ≈ 12.011 g/mol, H ≈ 1.008 g/mol, O ≈ 15.999 g/mol.
- Calculations per element:
- Carbon: 6 atoms × 12.011 g/mol = 72.066 g/mol
- Hydrogen: 12 atoms × 1.008 g/mol = 12.096 g/mol
- Oxygen: 6 atoms × 15.999 g/mol = 95.994 g/mol
- Summation: 72.066 g/mol + 12.096 g/mol + 95.994 g/mol = 180.156 g/mol
Outputs:
- Molecular Weight: 180.156 g/mol
- Total Atoms: 24
- Unique Elements: 3
- Atomic Weight Sum: 180.156 g/mol
Interpretation: One mole of glucose weighs approximately 180.156 grams. This is vital for understanding metabolic processes, calculating dosages in pharmaceuticals, and formulating nutritional supplements. The exact molecular weight is a cornerstone for quantitative analysis in biochemistry and organic chemistry.
How to Use This Exact Molecular Weight Calculator
Using this exact molecular weight calculator is simple and efficient. Follow these steps to get your results:
- Enter Chemical Formula: In the "Chemical Formula" input field, type the chemical formula of the compound you want to analyze. Use standard element symbols (e.g., 'H', 'O', 'C', 'Na') and number subscripts (e.g., '2' for H₂, '6' for C₆). For example, enter 'H2O' for water or 'C6H12O6' for glucose.
- Dynamic Input Generation: As you type a valid formula, the calculator will attempt to parse it and dynamically generate input fields for each unique element found, pre-filling the atom counts. If the formula is complex or contains potential ambiguities, you might need to manually adjust the counts.
- Verify or Input Atomic Weights: The calculator uses standard atomic weights. If you need to use specific isotopic masses or a different set of values, you may need to manually input them into the generated element fields. Ensure the units are consistent (g/mol).
- Calculate: Click the "Calculate Molecular Weight" button.
Reading the Results:
- Primary Result (Molecular Weight): The largest, most prominent number is the calculated molecular weight in grams per mole (g/mol).
- Intermediate Values: Below the main result, you'll find key metrics like the total number of atoms in the molecule, the count of unique elements, and the sum of atomic weights before final calculation, providing transparency into the process.
- Formula Explanation: A brief explanation of the underlying formula is provided for clarity.
Decision-Making Guidance:
The calculated molecular weight is a definitive value for a given compound under standard conditions. It's essential for:
- Reaction Stoichiometry: Determining the precise amounts of reactants needed or products formed.
- Solution Preparation: Calculating molarity (moles per liter) requires knowing the molecular weight to convert mass to moles.
- Compound Identification: Comparing experimental data (e.g., mass spectrometry) with calculated values.
- Experimental Design: Ensuring accurate quantities are used in laboratory procedures.
Use the "Copy Results" button to easily transfer these key values to your notes, reports, or other applications.
Key Factors That Affect Molecular Weight Calculations
While the calculation itself is deterministic based on a formula, several underlying factors and considerations influence the precision and interpretation of the exact molecular weight:
- Isotopic Abundance: Standard atomic weights are averages based on the natural isotopic abundance of an element. Different sources might use slightly varying isotopic data, leading to minor differences in calculated molecular weights. For highly precise applications, using isotopic masses rather than average atomic weights is necessary.
- Hydration/Solvation: Compounds can incorporate water molecules (hydrates) or solvent molecules within their crystal structure. For example, copper sulfate pentahydrate (CuSO₄·5H₂O) has a significantly different molecular weight than anhydrous copper sulfate (CuSO₄). Always ensure the formula reflects the exact form of the compound being considered.
- Purity of Sample: Impurities within a sample will alter its overall measured molar mass. The calculated molecular weight applies strictly to the pure compound. Any deviation in experimental measurements might indicate the presence of impurities.
- Atomic Weight Data Source: Different periodic tables or databases may provide atomic weights with varying levels of precision or use slightly different consensus values, particularly for elements with complex isotopic mixtures. Ensure consistency in the data source used for calculation.
- Molecular Formula Accuracy: The accuracy of the chemical formula itself is paramount. An incorrect formula, whether due to typos or misunderstanding the compound's structure (e.g., isomers), will lead directly to an incorrect molecular weight calculation.
- Units of Measurement: Atomic weights are typically provided in atomic mass units (amu) or grams per mole (g/mol). While numerically equivalent for practical purposes when calculating molar mass, consistency in using g/mol is standard for macroscopic chemical calculations.
- Polymerization: For polymers, the "molecular weight" is often a distribution (number average, weight average) rather than a single exact value, due to variations in chain length. This calculator is designed for discrete molecules, not polymer distributions.
Frequently Asked Questions (FAQ)
Q1: What is the difference between molecular weight and molar mass?
A1: Technically, molecular weight is the mass of a single molecule (in amu), while molar mass is the mass of one mole of a substance (in g/mol). However, they are numerically equivalent and often used interchangeably in general chemistry contexts. This calculator provides the value in g/mol, commonly referred to as molar mass.
Q2: Can this calculator handle complex chemical formulas with parentheses, like Ca(OH)₂?
A2: The current version of this calculator is designed to parse simpler formulas. For formulas with parentheses indicating polyatomic ions (like Ca(OH)₂), the calculator will interpret 'Ca', 'OH', and '2' separately. For Ca(OH)₂, you would manually input it as Ca: 1, O: 2, H: 2. We are working on enhancing the parsing capabilities for more complex structures.
Q3: What atomic weights does the calculator use?
A3: The calculator uses standard, internationally recognized atomic weights for elements, typically sourced from IUPAC (International Union of Pure and Applied Chemistry). These are average values reflecting natural isotopic abundance.
Q4: How precise is the "exact" molecular weight calculation?
A4: The precision is limited by the precision of the atomic weights used. Standard atomic weights are typically given to 3-5 decimal places. For even higher precision, one would need isotopic mass data, which this calculator does not directly use.
Q5: Can I calculate the molecular weight of ions or radicals?
A5: Yes, provided you know the correct chemical formula. For example, the sulfate ion (SO₄²⁻) has the formula SO4, and its molecular weight calculation is the same as for a neutral molecule. The charge does not affect the mass.
Q6: What units should I use for atomic weights if I input them manually?
A6: For consistency with the calculator's output, use grams per mole (g/mol). Atomic mass units (amu) are numerically equivalent for this purpose.
Q7: Does the calculator account for elements with multiple common isotopes?
A7: The calculator uses the *average* atomic weight based on natural isotopic abundance. It does not distinguish between specific isotopes (like Carbon-12 vs. Carbon-14) unless you manually override the atomic weight input for a specific element.
Q8: What is the importance of molecular weight in analytical chemistry?
A8: Molecular weight is crucial for identifying unknown compounds (e.g., via mass spectrometry), quantifying substances in solution (using molarity, which depends on molar mass), and verifying the composition of synthesized materials.
Related Tools and Internal Resources
- Exact Molecular Weight Calculator – Use our tool to instantly find the molar mass of any compound.
- Stoichiometry Calculator – Essential for balancing chemical equations and calculating reaction yields.
- Molarity Calculator – Determine solution concentrations accurately using molar mass.
- Periodic Table with Atomic Weights – Find detailed atomic information for all elements.
- Percent Composition Calculator – Calculate the mass percentage of each element within a compound.
- Empirical Formula Calculator – Determine the simplest whole-number ratio of atoms in a compound.
\
\
\
Standard atomic weight for {elementSymbol} is {atomicWeight} g/mol. Adjust if needed.\
\
';
function parseChemicalFormula(formula) {
var elements = {};
var regex = /([A-Z][a-z]?)(\d*)/g;
var match;
var totalAtoms = 0;
while ((match = regex.exec(formula)) !== null) {
var elementSymbol = match[1];
var countStr = match[2];
var count = countStr === " ? 1 : parseInt(countStr, 10);
if (isNaN(count)) {
throw new Error("Invalid count in formula: " + formula);
}
if (!(elementSymbol in atomicWeights)) {
throw new Error("Unknown element symbol: " + elementSymbol);
}
if (elements[elementSymbol]) {
elements[elementSymbol].count += count;
} else {
elements[elementSymbol] = {
atomicWeight: atomicWeights[elementSymbol],
count: count
};
}
totalAtoms += count;
}
return { elements: elements, totalAtoms: totalAtoms };
}
function updateElementInputs() {
var formulaInput = document.getElementById('chemicalFormula');
var formula = formulaInput.value.trim();
var container = document.getElementById('elementInputsContainer');
container.innerHTML = "; // Clear previous inputs
if (!formula) {
return;
}
try {
var parsed = parseChemicalFormula(formula);
var uniqueElements = Object.keys(parsed.elements).length;
var allElementsValid = true;
for (var elementSymbol in parsed.elements) {
var data = parsed.elements[elementSymbol];
var html = elementInputTemplate
.replace(/\{elementSymbol\}/g, elementSymbol)
.replace(/\{atomicWeight\}/g, data.atomicWeight)
.replace(/\{count\}/g, data.count)
.replace(/\{minVal\}/g, 0)
.replace(/\{maxVal\}/g, 99999); // Arbitrary large max
container.innerHTML += html;
}
document.getElementById('uniqueElementsResult').textContent = uniqueElements;
document.getElementById('totalAtomsResult').textContent = parsed.totalAtoms;
} catch (error) {
formulaInput.setCustomValidity(error.message); // Should be handled by inline error display too
document.getElementById('chemicalFormulaError').textContent = error.message;
document.getElementById('chemicalFormulaError').classList.add('visible');
document.getElementById('uniqueElementsResult').textContent = '0';
document.getElementById('totalAtomsResult').textContent = '0';
container.innerHTML = "; // Clear inputs if formula is invalid
return false;
}
return true;
}
function calculateMolecularWeight() {
var formulaInput = document.getElementById('chemicalFormula');
var formulaError = document.getElementById('chemicalFormulaError');
formulaError.classList.remove('visible');
formulaInput.setCustomValidity(");
if (!updateElementInputs()) {
// Error already displayed by updateElementInputs
return;
}
var totalMolecularWeight = 0;
var atomicWeightSum = 0;
var numAtoms = 0;
var elementInputs = document.querySelectorAll('.element-input');
if (elementInputs.length === 0 && formulaInput.value.trim() !== "") {
// This case should ideally be caught by updateElementInputs
formulaError.textContent = "Could not parse formula. Please check format.";
formulaError.classList.add('visible');
return;
} else if (elementInputs.length === 0 && formulaInput.value.trim() === "") {
// No formula entered, do nothing until input
return;
}
for (var i = 0; i < elementInputs.length; i++) {
var inputGroup = elementInputs[i];
var elementSymbol = inputGroup.id.replace('elementInput_', '');
var atomicWeightInput = document.getElementById('elementSymbol_' + elementSymbol);
var atomicWeightError = document.getElementById('elementInputError_' + elementSymbol);
atomicWeightError.classList.remove('visible');
var atomicWeightVal = parseFloat(atomicWeightInput.value);
var elementCount = parseInt(atomicWeightInput.getAttribute('data-count') || '1'); // Fallback if not set
if (isNaN(atomicWeightVal) || atomicWeightVal < 0) {
atomicWeightError.textContent = "Please enter a valid non-negative number.";
atomicWeightError.classList.add('visible');
atomicWeightVal = 0; // Set to 0 to prevent NaN in sum
}
// Get the count from the original formula parsing, if available
var formula = formulaInput.value.trim();
var regex = new RegExp('([A-Z][a-z]?)(\\d*)', 'g');
var match;
var currentElementCount = 0;
while((match = regex.exec(formula)) !== null) {
if (match[1] === elementSymbol) {
currentElementCount = match[2] === '' ? 1 : parseInt(match[2], 10);
break;
}
}
var weightContribution = atomicWeightVal * currentElementCount;
totalMolecularWeight += weightContribution;
atomicWeightSum += atomicWeightVal; // This sum might not be directly useful, depends on interpretation
numAtoms += currentElementCount;
}
document.getElementById('molecularWeightResult').textContent = totalMolecularWeight.toFixed(3);
document.getElementById('atomicWeightSumResult').textContent = totalMolecularWeight.toFixed(3); // Re-using for consistency
// document.getElementById('totalAtomsResult').textContent = numAtoms; // Already set by updateElementInputs
document.getElementById('result').style.display = 'flex';
document.getElementById('intermediateResultsContainer').style.display = 'flex';
// Update chart data
updateChart(totalMolecularWeight, atomicWeightSum);
}
function validateInput(input, min, max, errorId, fieldName) {
var errorElement = document.getElementById(errorId);
var value = parseFloat(input.value);
errorElement.classList.remove('visible');
input.setCustomValidity('');
if (isNaN(value)) {
errorElement.textContent = "Please enter a valid number.";
errorElement.classList.add('visible');
input.value = ''; // Clear invalid input
return false;
}
if (value max) {
// errorElement.textContent = fieldName + " is unusually high.";
// errorElement.classList.add('visible');
// // Don't reset value here, just show warning
// return false;
// }
return true;
}
function resetCalculator() {
document.getElementById('chemicalFormula').value = ";
document.getElementById('elementInputsContainer').innerHTML = ";
document.getElementById('result').style.display = 'none';
document.getElementById('intermediateResultsContainer').style.display = 'none';
document.getElementById('chemicalFormulaError').classList.remove('visible');
document.getElementById('molecularWeightResult').textContent = '0.00';
document.getElementById('totalAtomsResult').textContent = '0';
document.getElementById('uniqueElementsResult').textContent = '0';
document.getElementById('atomicWeightSumResult').textContent = '0.00';
// Reset canvas
var canvas = document.getElementById('molecularWeightChart');
if (canvas) {
var ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
}
function copyResults() {
var molecularWeight = document.getElementById('molecularWeightResult').textContent;
var unit = document.querySelector('#result .unit').textContent;
var formulaExplanation = document.querySelector('#result .formula-explanation').textContent;
var totalAtoms = document.getElementById('totalAtomsResult').textContent;
var uniqueElements = document.getElementById('uniqueElementsResult').textContent;
var atomicWeightSum = document.getElementById('atomicWeightSumResult').textContent;
var formula = document.getElementById('chemicalFormula').value;
var textToCopy = "Molecular Weight Calculation Results:\n";
textToCopy += "————————————–\n";
textToCopy += "Chemical Formula: " + (formula || "N/A") + "\n";
textToCopy += "Molecular Weight: " + molecularWeight + " " + unit + "\n";
textToCopy += "Formula Used: " + formulaExplanation + "\n\n";
textToCopy += "Key Intermediate Values:\n";
textToCopy += "- Total Atoms: " + totalAtoms + "\n";
textToCopy += "- Unique Elements: " + uniqueElements + "\n";
textToCopy += "- Atomic Weight Sum (as calculated): " + atomicWeightSum + " " + unit + "\n";
textToCopy += "————————————–\n";
textToCopy += "Note: Calculations based on standard atomic weights.";
// Use a temporary textarea for copying
var textArea = document.createElement("textarea");
textArea.value = textToCopy;
textArea.style.position = "fixed";
textArea.style.left = "-9999px";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'Results copied successfully!' : 'Failed to copy results.';
// Optional: Show a temporary message to the user
// alert(msg);
} catch (err) {
// Optional: Show error message
// alert('Oops, unable to copy');
}
document.body.removeChild(textArea);
}
// Charting Logic
var molecularWeightChart;
var chartContext;
function initializeChart() {
var canvas = document.createElement('canvas');
canvas.id = 'molecularWeightChart';
// Insert canvas before the first article section or after results
var resultDiv = document.getElementById('result');
if (resultDiv && resultDiv.parentNode) {
// Insert after result div
resultDiv.parentNode.insertBefore(canvas, resultDiv.nextSibling);
} else {
// Fallback if result div is not found
var container = document.querySelector('.container main');
container.appendChild(canvas);
}
chartContext = canvas.getContext('2d');
molecularWeightChart = new Chart(chartContext, {
type: 'bar', // Or 'pie', 'doughnut' depending on preference
data: {
labels: [], // Will be populated with element symbols
datasets: [{
label: 'Atomic Contribution (g/mol)',
data: [], // Will be populated with calculated values per element
backgroundColor: [], // Colors for bars
borderColor: [],
borderWidth: 1
}]
},
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
y: {
beginAtZero: true,
title: {
display: true,
text: 'Mass Contribution (g/mol)'
}
},
x: {
title: {
display: true,
text: 'Element'
}
}
},
plugins: {
title: {
display: true,
text: 'Contribution of Each Element to Molecular Weight'
},
legend: {
display: true
}
}
}
});
}
function updateChart(totalMW, atomicWeightSum) {
var canvas = document.getElementById('molecularWeightChart');
if (!canvas) {
// Canvas doesn't exist yet, create it and the chart
initializeChart();
canvas = document.getElementById('molecularWeightChart'); // Re-get the element after creation
}
chartContext = canvas.getContext('2d');
var formulaInput = document.getElementById('chemicalFormula');
var formula = formulaInput.value.trim();
var data = {
labels: [],
datasets: [{
label: 'Atomic Contribution (g/mol)',
data: [],
backgroundColor: [],
borderColor: [],
borderWidth: 1
}]
};
if (formula) {
try {
var parsed = parseChemicalFormula(formula);
var colors = generateColors(Object.keys(parsed.elements).length); // Generate colors dynamically
for (var elementSymbol in parsed.elements) {
var elementData = parsed.elements[elementSymbol];
var elementAtomicWeight = parseFloat(document.getElementById('elementSymbol_' + elementSymbol).value);
var contribution = elementAtomicWeight * elementData.count;
data.labels.push(elementSymbol);
data.datasets[0].data.push(contribution.toFixed(3));
data.datasets[0].backgroundColor.push(colors[elementSymbol].bg);
data.datasets[0].borderColor.push(colors[elementSymbol].border);
}
} catch (e) {
// If formula parsing fails, clear the chart data
data.labels = [];
data.datasets[0].data = [];
}
}
// Update chart data and redraw
if (molecularWeightChart) {
molecularWeightChart.data = data;
molecularWeightChart.options.plugins.title.text = 'Contribution of Each Element to Molecular Weight';
molecularWeightChart.update();
} else {
// Should not happen if initializeChart works correctly
console.error("Chart object not found.");
}
}
function generateColors(count) {
var generatedColors = {};
var baseColors = [
{ bg: 'rgba(54, 162, 235, 0.6)', border: 'rgba(54, 162, 235, 1)' }, // Blue
{ bg: 'rgba(255, 99, 132, 0.6)', border: 'rgba(255, 99, 132, 1)' }, // Red
{ bg: 'rgba(75, 192, 192, 0.6)', border: 'rgba(75, 192, 192, 1)' }, // Green
{ bg: 'rgba(255, 206, 86, 0.6)', border: 'rgba(255, 206, 86, 1)' }, // Yellow
{ bg: 'rgba(153, 102, 255, 0.6)', border: 'rgba(153, 102, 255, 1)' }, // Purple
{ bg: 'rgba(255, 159, 64, 0.6)', border: 'rgba(255, 159, 64, 1)' }, // Orange
{ bg: 'rgba(199, 199, 199, 0.6)', border: 'rgba(199, 199, 199, 1)' }, // Gray
{ bg: 'rgba(8, 198, 123, 0.6)', border: 'rgba(8, 198, 123, 1)' }, // Teal
{ bg: 'rgba(230, 102, 230, 0.6)', border: 'rgba(230, 102, 230, 1)' }, // Pink
{ bg: 'rgba(100, 150, 200, 0.6)', border: 'rgba(100, 150, 200, 1)' } // Light Blue-ish
];
for (var i = 0; i 0){
calculateMolecularWeight();
}
} else {
// If formula itself is invalid, clear results and intermediate values
document.getElementById('result').style.display = 'none';
document.getElementById('intermediateResultsContainer').style.display = 'none';
document.getElementById('uniqueElementsResult').textContent = '0';
document.getElementById('totalAtomsResult').textContent = '0';
// Clear the chart if the formula becomes invalid
var canvas = document.getElementById('molecularWeightChart');
if (canvas) {
var ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
}
});
// Ensure calculation happens on initial load if default value exists (optional)
// calculateMolecularWeight();