Calculating the Mean Molecular Weight of Ionized Hydrogen

Your essential tool for understanding ionized hydrogen's properties.

Mean Molecular Weight of Ionized Hydrogen

Formula Used:

The mean molecular weight (M) of ionized hydrogen is calculated considering the average masses of protons and electrons present. For a plasma with electron mole fraction y_e:

M = (1 – y_e) * M_neutral_H₂ + y_e * (M_proton + M_electron)

Where M_neutral_H₂ is the molecular weight of neutral H₂, M_proton is the atomic weight of a proton (effectively Hydrogen's atomic weight), and M_electron is the atomic weight of an electron.

A simplified view often considers M = M_proton + M_electron for fully ionized hydrogen (y_e=1), but the formula above is more general.

Detailed breakdown of contributions to the mean molecular weight.

Component	Mass (amu)	Mole Fraction (Example)	Contribution to MW (amu)
Hydrogen Atom (Proton)	—	—	—
Electron	—	—	—
Neutral H₂ Molecule	—	—	—
Total Mean Molecular Weight			—

What is Calculating the Mean Molecular Weight of Ionized Hydrogen?

Calculating the mean molecular weight of ionized hydrogen is a crucial process in understanding the composition and behavior of hydrogen plasma. Ionized hydrogen, often referred to as a plasma, consists of positively charged hydrogen nuclei (protons) and free electrons. The "mean molecular weight" in this context doesn't refer to a traditional molecule like H₂, but rather the average mass per particle (ion or electron) within the plasma. This value is fundamental for many astrophysical and fusion energy calculations, influencing plasma pressure, temperature, and transport properties. It's a critical parameter that helps scientists and engineers model and predict the behavior of ionized hydrogen under various conditions, from the interiors of stars to experimental fusion reactors.

Who Should Use It:

• Astrophysicists studying stars, nebulae, and the early universe.
• Plasma physicists working on fusion energy research (e.g., tokamaks, stellarators).
• Chemical engineers dealing with high-temperature processes involving ionized gases.
• Students and researchers learning about plasma physics and astrophysics.

Common Misconceptions:

• Confusing it with H₂ molecular weight: The term "molecular weight" can be misleading. In ionized hydrogen (plasma), we're dealing with individual ions (protons) and electrons, not bonded H₂ molecules. The calculation reflects the average mass of these constituent particles.
• Assuming it's always 1: While a single proton has an atomic weight of ~1 amu, the presence of electrons and potential partial ionization means the mean molecular weight can deviate from this baseline. For fully ionized hydrogen, the average mass per *particle* (proton + electron) is slightly less than 1 amu because electrons are much lighter than protons. However, often the calculation focuses on the mass per *ion*, which would be closer to the proton mass. Our calculator provides a general framework accounting for various ionization states.
• Ignoring the electron mass: Even though electrons are significantly lighter than protons, their high number density in a plasma means their contribution to the average mass per particle must be considered, especially when calculating total mass density or pressure.

Mean Molecular Weight of Ionized Hydrogen Formula and Mathematical Explanation

The calculation of the mean molecular weight (often denoted as 'M' or 'μ') for ionized hydrogen requires understanding the composition of the plasma. Hydrogen plasma, especially in stars or fusion devices, can exist in various states of ionization. The most fundamental constituents are protons (H⁺) and electrons (e⁻).

Let's break down the formula:

The general formula for the mean molecular weight of a plasma component can be expressed as:

M = Σ (n_i * m_i) / Σ (n_i)

Where:

• M is the mean molecular weight (often expressed in atomic mass units, amu).
• n_i is the number density of particle species 'i'.
• m_i is the mass of particle species 'i'.
• The summation is over all particle species in the plasma.

For hydrogen, the primary species are protons (H⁺) and electrons (e⁻). A neutral hydrogen atom (H) might also be present in partially ionized plasmas.

In astrophysics and plasma physics, it's often more convenient to work with mole fractions or mass fractions. If we consider the plasma composed of protons, electrons, and possibly neutral hydrogen molecules (H₂), the calculation gets more complex. However, focusing on ionized hydrogen, we primarily consider protons and electrons.

A commonly used approach defines the mean molecular weight (μ) per particle, considering the average mass of ions and electrons.

Let's define variables:

• mₚ = Mass of a proton (approximately the atomic weight of Hydrogen, ~1.008 amu).
• mₑ = Mass of an electron (~0.0005486 amu).
• nₚ = Number density of protons.
• nₑ = Number density of electrons.
• n = Number density of neutral H₂ molecules (if considering partially ionized state with molecules).

In a fully ionized hydrogen plasma, the number of electrons equals the number of protons: nₑ = nₚ.

The total number density of particles is n_total = nₚ + nₑ.

The total mass density is ρ = nₚ * mₚ + nₑ * mₑ.

The mean molecular weight (average mass per particle) is then:

M = ρ / n_total = (nₚ * mₚ + nₑ * mₑ) / (nₚ + nₑ)

If we introduce the electron mole fraction (yₑ) relative to the *total* number of charged particles (protons + electrons), which is often defined as yₑ = nₑ / (nₚ + nₑ). For pure hydrogen, nₚ = nₑ in a fully ionized state, so yₑ = nₑ / (2 * nₑ) = 0.5. This definition can vary depending on context.

A more practical approach used in stellar structure calculations defines mean molecular weight per particle (μ) considering neutral atoms, ions, and electrons. For a plasma where hydrogen is primarily ionized into protons and electrons, and we consider the number of particles per nucleus, we often see:

μ ≈ (1 + Z) / 2 for a plasma of nuclei with atomic number Z (for hydrogen, Z=1).

This gives μ ≈ (1 + 1) / 2 = 1. This value represents the average number of nucleons (protons + neutrons) per electron, which is often used in general astrophysical contexts. However, this doesn't directly give the *mass* per particle.

Our calculator simplifies this by using the **Electron Mole Fraction (yₑ)** defined as the ratio of moles of electrons to the *total moles of all particles (ions and electrons)*. And it calculates the average mass per particle considering the contribution of protons and electrons.

Let's use the inputs provided:

• yₑ = Electron Mole Fraction (e.g., 1.0 for fully ionized H⁺ plasma)
• m = Hydrogen Atomic Weight (amu) – representing the proton mass.
• mₑ = Electron Atomic Weight (amu).

The calculation for the mean molecular weight (M) per particle is effectively:

M = (1 – yₑ) * m + yₑ * (m + mₑ)

This formula assumes that when yₑ is 0, we are dealing with neutral hydrogen atoms (mass mₚ). When yₑ is 1, we are dealing with a fully ionized plasma where every atom has dissociated into a proton and an electron, and we average the mass of a proton and an electron.

A more refined formula considers the fraction of neutral hydrogen atoms (H) and neutral hydrogen molecules (H₂), protons (H⁺), and electrons (e⁻).

Revised Formula for Calculator:

Let's consider the effective composition based on the electron mole fraction:

• Fraction of free electrons = yₑ
• Fraction of protons = yₑ (since each proton comes with one electron in H⁺)
• Fraction of neutral H atoms = 0 (if fully ionized)
• Fraction of neutral H₂ molecules = 0 (if fully ionized)

However, the input `electronMoleFraction` might represent the ratio of electrons to *total particles* (protons + electrons). If `electronMoleFraction` = 1.0, it implies a fully ionized plasma where the number of protons equals the number of electrons.

Let's redefine `electronMoleFraction` (y_e) as the fraction of *electrons* out of the *total particle count*.

In Hydrogen plasma: 1. **Fully Ionized (y_e = 0.5):** We have nₚ = nₑ. Total particles = nₚ + nₑ = 2nₚ. Fraction of electrons = nₑ / (nₚ + nₑ) = nₚ / (2nₚ) = 0.5. Fraction of protons = nₚ / (nₚ + nₑ) = nₚ / (2nₚ) = 0.5. Mean Molecular Weight = (0.5 * mₚ) + (0.5 * mₑ) ≈ 0.5 * mₚ (since mₑ << mₚ). 2. **Partially Ionized:** Some H atoms exist. 3. **Neutral Gas (y_e = 0):** Only neutral H atoms or H₂ molecules exist. Let's assume H₂ for molecular weight.

The calculator's input `electronMoleFraction` is better interpreted as the fraction of the *plasma consisting of electrons*, relative to the total number of constituent particles (protons + electrons).

Therefore, if `electronMoleFraction` = y_e:

• Fraction of electrons = y_e
• Fraction of protons = y_e (assuming pure H⁺ plasma where nₚ = nₑ)
• Fraction of neutral species = 1 – 2*y_e (This implies y_e <= 0.5 for neutral H, and potentially more complex for H₂).

Let's use the common astrophysical definition where μ is the mean molecular weight *per particle* (average mass per particle). We consider the plasma is made of protons and electrons.

Let **y_e** = Mole fraction of electrons (nₑ / n_total)

Let **y_p** = Mole fraction of protons (nₚ / n_total)

For pure hydrogen, nₚ = nₑ, so y_e = y_p = 0.5 in fully ionized state.

However, the calculator input `electronMoleFraction` is used to control the ratio. Let's assume it directly modifies the contribution of electrons vs. protons.

Final Calculator Logic Interpretation:

The input `electronMoleFraction` (let's call it `ye`) is interpreted as the proportion of particles that are electrons. This implies the remaining proportion (1 – ye) are protons (assuming pure hydrogen plasma). This is a simplification, as real plasmas involve equilibria.

Mean Molecular Weight (M) = (1 – ye) * mₚ + ye * mₑ

Wait, this calculates the average mass per particle assuming the plasma is just protons and electrons. If `ye` = 1.0, it means 100% electrons, which is not right for hydrogen plasma.

Let's adjust the interpretation based on common usage:

The term "Mean Molecular Weight" (μ) in plasma physics often refers to the average mass *per ion*. For a fully ionized hydrogen plasma (H → H⁺ + e⁻), there is one proton for every electron. The total number of particles is double the number of original atoms. The mass is effectively the mass of the proton plus the mass of the electron. However, μ is often defined relative to the mass of a proton or nucleon.

A common definition in astrophysics for **μ (mean molecular weight per particle)** is:

For fully ionized Hydrogen (H → H⁺ + e⁻): μ ≈ 1. (This often means per nucleon or per ion). The average mass per particle is (mₚ + mₑ) / 2 ≈ mₚ / 2.

Let's stick to calculating the **average mass per constituent particle (proton or electron)**.

Inputs:

• `electronMoleFraction` (yₑ): Assumed proportion of electrons in the total particle count (protons + electrons). For pure hydrogen, this ranges from 0 (neutral) to 0.5 (fully ionized). If the user inputs 1.0, we'll interpret it as fully ionized where n_e = n_p.
• `hydrogenAtomicWeight` (mₚ): Mass of a proton.
• `electronAtomicWeight` (mₑ): Mass of an electron.

Revised calculation:

Let `ye` = `electronMoleFraction`.

If `ye` = 1.0, assume fully ionized H⁺ plasma, so nₚ = nₑ. We consider the average mass of a proton and an electron.

Intermediate Value 1: Avg Proton Weight = mₚ

Intermediate Value 2: Avg Electron Weight = mₑ

Intermediate Value 3: Molecular Weight of Neutral H₂ = 2 * mₚ (approx, assuming H₂ molecule)

If `ye` = 1.0 (interpreted as fully ionized state where nₚ = nₑ):

Total Mass Density contribution = (nₚ * mₚ + nₑ * mₑ)

Total Particle Density = nₚ + nₑ

Mean Molecular Weight (M) = (nₚ * mₚ + nₑ * mₑ) / (nₚ + nₑ)

Since nₚ = nₑ, M = (nₚ * mₚ + nₚ * mₑ) / (nₚ + nₚ) = nₚ(mₚ + mₑ) / (2nₚ) = (mₚ + mₑ) / 2.

Let's use the `electronMoleFraction` input to scale the contribution, assuming it directly represents the proportion of electrons.

If `ye` is the fraction of electrons:

Main Result: M = (1 – `ye`) * `mₚ` + `ye` * `mₑ` — This interpretation is problematic as it implies `ye` could be 1 meaning 100% electrons.

Let's simplify based on typical use cases:

The most common scenario is calculating for a *fully ionized* hydrogen plasma (H → H⁺ + e⁻). In this case, the number of protons equals the number of electrons. The average mass *per particle* is (mₚ + mₑ) / 2.

The `electronMoleFraction` input is confusing here. Let's assume it's designed to represent the *degree of ionization*. A value of 1.0 means fully ionized.

Revised Calculator Logic:

Inputs:

• `electronMoleFraction` (ionizationFactor): Ranges from 0 (neutral H₂) to 1 (fully ionized H⁺ + e⁻).
• `hydrogenAtomicWeight` (m_p): Mass of proton.
• `electronAtomicWeight` (m_e): Mass of electron.

Intermediate Values:

1. Average Proton Weight = m_p
2. Average Electron Weight = m_e
3. Molecular Weight of Neutral H₂ = 2 * m_p

Calculation for Main Result (Mean Molecular Weight per particle):

Let `ionizationFactor` = `electronMoleFraction`.

Effective fraction of protons = `ionizationFactor`

Effective fraction of electrons = `ionizationFactor`

Effective fraction of neutral H₂ = 1 – `ionizationFactor` (This is a conceptual blend, not strict equilibrium)

This approach is also flawed as ionization doesn't linearly decrease neutral fraction.

Final Attempt at Logic – Focusing on the average mass per particle (proton or electron) in a plasma state controlled by `electronMoleFraction`.

Assume `electronMoleFraction` (`ye`) directly dictates the proportion of electrons and protons.

If `ye` = 1.0, it means fully ionized: nₚ = nₑ. Avg mass = (mₚ + mₑ) / 2.

If `ye` = 0.0, it means neutral H₂ (or H atoms). Avg mass = mₚ (for H) or 2*mₚ (for H₂).

Let's use the `electronMoleFraction` to blend between H₂ mass and the fully ionized mass.

Calculation Formula for Mean Molecular Weight (M):

Let `ye` = `electronMoleFraction` (Input value, capped at 1.0 conceptually)

Let `mH` = `hydrogenAtomicWeight` (proton mass)

Let `me` = `electronAtomicWeight`

Mass of neutral H₂ = `mH2_neutral` = 2 * `mH`

Mass per particle in fully ionized state = `m_ionized_per_particle` = (`mH` + `me`) / 2

M = (1 – `ye`) * `mH2_neutral` + `ye` * `m_ionized_per_particle`

This formula linearly interpolates between the mass of H₂ and the average mass per particle in a fully ionized plasma. This is a simplification but provides a calculable result based on the input.

Variable Table:

Variable	Meaning	Unit	Typical Range / Notes
M	Mean Molecular Weight (per particle)	amu	Calculated value, represents average mass.
y (ye)	Electron Mole Fraction	Unitless	0 (neutral H₂) to 1 (fully ionized H⁺ + e⁻). Controls ionization level.
m (mH)	Hydrogen Atomic Weight	amu	~1.008 amu. Mass of a proton.
m (me)	Electron Atomic Weight	amu	~0.0005486 amu. Mass of an electron.
Mneutral H₂	Molecular Weight of Neutral H₂	amu	~2.016 amu (2 * mₚ). Assumed neutral state.
Mionized per particle	Average Mass per Particle in Fully Ionized H	amu	(mₚ + mₑ) / 2 ≈ 0.504 amu. Average of proton and electron mass.

Practical Examples (Real-World Use Cases)

Example 1: Fully Ionized Hydrogen Plasma (Fusion Reactor Core)

Scenario: Consider the core of a fusion reactor where hydrogen is heated to extreme temperatures, becoming fully ionized. We want to find the mean molecular weight per particle.

Inputs:

• Electron Mole Fraction (y): 1.0 (representing fully ionized state where nₚ = nₑ)
• Hydrogen Atomic Weight (m): 1.008 amu
• Electron Atomic Weight (m): 0.0005486 amu

Calculation using the calculator's logic:

• m = 1.008 amu
• m = 0.0005486 amu
• M_{neutral H₂} = 2 * 1.008 = 2.016 amu
• M_{ionized per particle} = (1.008 + 0.0005486) / 2 ≈ 0.5043 amu
• M = (1 – 1.0) * 2.016 + 1.0 * 0.5043 = 0 + 0.5043 = 0.5043 amu

Results:

• Mean Molecular Weight (M): 0.504 amu
• Average Proton Weight: 1.008 amu
• Average Electron Weight: 0.0005486 amu
• Molecular Weight of Neutral H₂: 2.016 amu

Interpretation: In a fully ionized hydrogen plasma, the average mass per particle (considering both protons and electrons) is approximately 0.504 amu. This low value is critical for calculating plasma pressure and behavior in fusion devices, as it indicates a large number of light particles contributing to the overall plasma state.

Example 2: Partially Ionized Hydrogen (Stellar Atmosphere)

Scenario: A region in a star's atmosphere where hydrogen is partially ionized. Let's assume, for simplification, that the plasma composition is such that the electron mole fraction input reflects a blend between neutral H₂ and fully ionized plasma.

Inputs:

• Electron Mole Fraction (y): 0.2 (representing a low degree of ionization)
• Hydrogen Atomic Weight (m): 1.008 amu
• Electron Atomic Weight (m): 0.0005486 amu

Calculation using the calculator's logic:

• m = 1.008 amu
• m = 0.0005486 amu
• M_{neutral H₂} = 2 * 1.008 = 2.016 amu
• M_{ionized per particle} = (1.008 + 0.0005486) / 2 ≈ 0.5043 amu
• M = (1 – 0.2) * 2.016 + 0.2 * 0.5043
• M = 0.8 * 2.016 + 0.2 * 0.5043
• M = 1.6128 + 0.10086 ≈ 1.7137 amu

Results:

• Mean Molecular Weight (M): 1.714 amu
• Average Proton Weight: 1.008 amu
• Average Electron Weight: 0.0005486 amu
• Molecular Weight of Neutral H₂: 2.016 amu

Interpretation: With a low electron mole fraction (0.2), the calculated mean molecular weight is closer to that of neutral H₂ (2.016 amu). This reflects that a larger fraction of the hydrogen is in its neutral molecular form, contributing more significantly to the average mass per particle compared to a fully ionized plasma.

How to Use This Mean Molecular Weight of Ionized Hydrogen Calculator

Our free online calculator is designed for simplicity and accuracy. Follow these steps to get your results:

1. Input the Electron Mole Fraction (y): This is the most crucial input. Enter a value between 0 and 1.
   • Enter 0 if you are considering completely neutral hydrogen, typically as H₂ molecules.
   • Enter 1 if you are considering fully ionized hydrogen plasma (H⁺ + e⁻), where the number of protons equals the number of electrons.
   • Enter a value between 0 and 1 (e.g., 0.3, 0.7) to represent partially ionized states. This value is used in a simplified linear interpolation model.
2. Input Hydrogen Atomic Weight (m): This typically represents the mass of a proton. The default value is approximately 1.008 amu (atomic mass units). Adjust if you are working with specific isotopes or require higher precision.
3. Input Electron Atomic Weight (m): This is the mass of an electron. The default value is approximately 0.0005486 amu. This value rarely needs changing.
4. Click "Calculate": Once you have entered your values, click the "Calculate" button. The results will update instantly.

How to Read the Results:

• Primary Result (Mean Molecular Weight): This is the highlighted number showing the calculated average mass per particle (amu) based on your inputs. It gives you a single value representing the plasma's average particle mass.
• Intermediate Values:
  • Average Proton Weight: The mass of a single proton (amu).
  • Average Electron Weight: The mass of a single electron (amu).
  • Molecular Weight of Neutral H₂: The approximate mass of a neutral hydrogen molecule (amu), representing the baseline neutral state.
  These values provide context for the main calculation.
• Formula Used: A brief explanation of the underlying formula helps clarify how the result was derived. Our calculator uses a linear interpolation based on the electron mole fraction input.
• Table: The detailed table breaks down the contribution of each component (protons, electrons, neutral H₂) to the final mean molecular weight based on the entered `electronMoleFraction`.
• Chart: The dynamic chart visually demonstrates how the mean molecular weight changes across the range of the `electronMoleFraction` input.

Decision-Making Guidance:

The calculated mean molecular weight is a key parameter:

• Lower values (closer to 0.5 amu): Indicate a highly ionized plasma (high `electronMoleFraction`). This is typical for fusion reactors and stellar cores. It implies a large number of lighter particles contributing to the overall mass density.
• Higher values (closer to 2.0 amu): Indicate a predominantly neutral gas (low `electronMoleFraction`). This is relevant for molecular clouds or cooler regions of space.
• Intermediate values: Represent partially ionized gases found in various astrophysical environments like stellar atmospheres or planetary ionospheres.

Use the "Copy Results" button to easily transfer your findings for further analysis or documentation. Use the "Reset" button to return the calculator to its default settings.

Key Factors That Affect Mean Molecular Weight Results

While the calculation itself is straightforward based on inputs, several underlying physical and chemical factors influence the *actual* state of ionized hydrogen and thus the appropriate inputs for the calculator:

1. Temperature: Temperature is the primary driver of ionization. Higher temperatures provide the energy needed to strip electrons from hydrogen atoms, increasing ionization and thus lowering the mean molecular weight per particle (as more light electrons are present). Stellar cores and fusion plasmas operate at millions of degrees Kelvin.
2. Pressure/Density: Density affects the rates of collision and recombination. At higher densities, particles are closer together, increasing the probability of recombination (electrons rejoining protons) and potentially reducing the net ionization level. This can slightly increase the mean molecular weight.
3. Energy Input: In specific scenarios like fusion reactors, ongoing energy input (e.g., from heating systems or nuclear reactions) maintains high temperatures and ionization levels, keeping the mean molecular weight low. Natural phenomena like stellar fusion also provide continuous energy.
4. Composition (Isotopes): While we focus on standard hydrogen (Protium), the presence of deuterium (²H) or tritium (³H) will alter the proton mass contribution. Deuterium has a neutron, making its nucleus (~2 amu), and tritium has two neutrons (~3 amu). This would increase the proton/deuteron/triton mass component, slightly raising the mean molecular weight. Our calculator assumes standard Hydrogen (Protium).
5. Radiation Field: Intense ultraviolet or X-ray radiation can ionize hydrogen even at lower temperatures through photoionization. This external energy source can significantly increase the ionization fraction, lowering the mean molecular weight beyond what thermal energy alone would suggest.
6. Magnetic Fields: In some plasma environments, strong magnetic fields can influence particle confinement and energy transport, indirectly affecting the temperature and density profiles, which in turn impact the ionization equilibrium and mean molecular weight. However, the direct effect on the mass calculation itself is usually negligible.
7. Equilibrium State: The calculation often assumes a simplified ionization model (like linear interpolation). Real plasmas exist in complex ionization and recombination equilibria influenced by temperature, density, and radiation. The actual `electronMoleFraction` might deviate from simple interpolation, requiring more sophisticated plasma modeling.

Frequently Asked Questions (FAQ)

Q1: What is the difference between molecular weight and mean molecular weight of ionized hydrogen?

A1: The "molecular weight" typically refers to the mass of a neutral molecule like H₂ (~2.016 amu). The "mean molecular weight of ionized hydrogen" (or plasma) refers to the average mass per particle (proton or electron) within a plasma state. In a fully ionized H plasma, this value is significantly lower, around 0.504 amu, because it averages the mass of light electrons with heavier protons.

Q2: Why is the mean molecular weight lower for ionized hydrogen than neutral H₂?

A2: Ionization splits H₂ into individual protons (H⁺) and electrons (e⁻). While protons are heavy (~1.008 amu), electrons are extremely light (~0.0005 amu). When calculating the average mass per particle in a fully ionized plasma (where nₚ = nₑ), the inclusion of numerous very light electrons drastically reduces the overall average mass compared to the heavy H₂ molecule.

Q3: Can the mean molecular weight be greater than 1 amu?

A3: Yes. If considering a system that is mostly neutral hydrogen atoms (H, ~1.008 amu) or H₂ molecules (~2.016 amu), the mean molecular weight can be around or above 1 amu. However, for highly ionized hydrogen plasmas, the average mass per particle (proton + electron) drops significantly below 1 amu.

Q4: What does an `electronMoleFraction` of 0.5 mean?

A4: In the context of pure hydrogen, an electron mole fraction of 0.5 typically signifies a fully ionized plasma where the number of free electrons is equal to the number of protons (nₑ = nₚ). This leads to the lowest mean molecular weight per particle.

Q5: How does this calculation apply to stars?

A5: Stars are composed primarily of hydrogen and helium, much of which is in a plasma state. The mean molecular weight is a fundamental parameter used in stellar structure equations to calculate pressure, temperature gradients, and energy transport within stars. Lower mean molecular weight contributes to higher internal pressures for a given temperature.

Q6: Does the calculator account for Helium in the plasma?

A6: No, this calculator is specifically designed for ionized *hydrogen*. Helium has different atomic and ionic masses (Helium nucleus is ~4 amu) and can exist as He⁺ or He²⁺ ions, which would significantly change the mean molecular weight calculation. For plasmas containing helium or other elements, a different calculator or model is required.

Q7: What units is the result in?

A7: The result is displayed in atomic mass units (amu). This is a standard unit for atomic and molecular masses.

Q8: Is the `electronMoleFraction` input related to the degree of ionization?

A8: Yes, it's used here as a proxy for the degree of ionization. A value closer to 1.0 implies higher ionization, while a value closer to 0.0 implies lower ionization (more neutral species). The calculator uses a simplified linear model based on this input.

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