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Decay Energy Calculator

Calculate decay energy online with steps. Find Q-value, mass difference, and nuclear decay energy in MeV, keV, eV, or joules.

Applies to Parent, Daughter and Alpha particle masses below.
u
Atomic mass of the parent nuclide, M(Z,N).
u
Atomic mass of the resulting daughter nuclide, M(Z-2,N-2).
u
Leave blank to use the standard ⁴He mass (4.002603254 u).
Applies to Parent and Daughter atomic masses below.
u
u
No electron-mass correction is needed here — atomic masses already account for it.
Applies to Parent and Daughter atomic masses below.
u
u
u
Leave blank to use the standard electron mass (0.00054857990907 u). Two electron masses are subtracted for β⁺ decay.
Applies to Parent and Daughter atomic masses below.
u
u
Binding energy of the captured atomic electron. Usually small (eV–keV) compared to Q; leave blank/0 if unknown.
Applies to the Parent mass and every Decay Product mass below.
u
Decay Products
u
Use this mode for any decay with multiple emitted particles (e.g. cluster decay, spontaneous fission) where the simple Q = M(parent) − ΣM(products) formula applies directly.
Published by a2zcalculators Team · 11 views

A Decay Energy Calculator finds the energy released in nuclear decay. It uses the mass of the parent and decay products. You can get the answer in MeV, keV, eV, or joules.

Our calculator makes this process quick. You don't need to solve each step by hand. Just enter the mass data and choose the decay type.

What Is Decay Energy?

Decay energy is the energy gained from a nuclear decay. It comes from a small loss of mass.

Think of mass as stored energy. When a nucleus changes, some mass may turn into energy. This energy can leave the atom as heat, light, or particle motion.

A positive decay energy means the decay can release energy.

This value is also called the Q-value.

Decay Energy Formula

The main decay energy formula is:

Decay Energy = Mass Difference × 931.494 MeV

First, find the mass difference:

Mass Difference = Parent Mass − Total Product Mass

Then use:

Q = Δm × 931.494 MeV

Here, Δm must be in atomic mass units, or u.

The value 931.494 MeV is the energy equal to one atomic mass unit.

For a general decay:

Q = (Parent Mass − Product Masses) × 931.494

For beta-plus decay, the electron mass needs a special correction.

For electron capture, the decay type also needs care. Our calculator handles these decay modes with separate rules.

How to Use Online Decay Energy Calculator

You can use our online Decay energy calculator with steps in a few simple steps.

  1. Choose the decay type. You can select alpha, beta-minus, beta-plus, electron capture, or general decay.
  2. Enter the parent mass. Select the unit that matches your data.
  3. Enter the daughter or product mass. Add all product masses for a general decay.
  4. Check the input data. The calculator changes the mass values to u when needed.
  5. Click calculate. The tool shows the mass change and decay energy.

The result can show MeV, keV, eV, and joules. This makes the tool useful for class work, lab work, and physics study.

Example Decay Energy Calculation

Let's use alpha decay as a simple example.

Suppose a parent has a mass of:

238.05078826 u

The daughter has a mass of:

234.043601 u

The alpha particle has a mass of:

4.002603254 u

First, find the mass change:

Δm = 238.05078826 − 234.043601 − 4.002603254

Δm ≈ 0.004583006 u

Now find the decay energy:

Q = 0.004583006 × 931.494

Q ≈ 4.27 MeV

So, the decay gives about:

4.27 MeV

To change MeV to joules:

Energy = 4.27 × 1.602176634 × 10⁻¹³

Energy ≈ 6.84 × 10⁻¹³ J

This shows how a tiny mass loss can give a large energy value.

Decay Energy Calculator Physics

The calculator is based on Einstein's mass-energy idea:

E = mc²

In nuclear physics, the mass change is very small. Yet the energy can be large.

The calculator uses atomic mass units to make nuclear mass work easy. It then changes the mass value into energy.

This makes the tool useful for nuclear decay problems. It can also help with Q-value calculations and nuclear reaction studies.

Final Verdict

Our Decay Energy Calculator makes nuclear decay math easy. It finds the mass change first. Then it turns that change into energy.

You can use it for alpha decay, beta decay, electron capture, and custom decay cases.

If you're solving a physics problem, this tool can save time. It also shows the key steps, so you can check the result with ease.

FAQs

What is a Decay Energy Calculator?

A Decay Energy Calculator finds the energy released or needed during nuclear decay. It uses mass change and the mass-energy relation.

What is the main decay energy formula?

The main formula is:

Q = Δm × 931.494 MeV

Here, Δm is the mass change in u.

What does a positive Q-value mean?

A positive Q-value means the decay can release energy. A negative value means energy input is needed.

What unit does decay energy use?

Decay energy is often given in MeV. You can also use keV, eV, or joules.

Why is 931.494 used?

One atomic mass unit has an energy value near 931.494 MeV. This lets you change mass loss into energy.

Can this calculator handle beta decay?

Yes. The calculator supports beta-minus and beta-plus decay. It also uses the needed electron mass rule for beta-plus decay.

Can I use kg instead of u?

Yes. The calculator can convert kg to atomic mass units before it finds the decay energy.

Is decay energy the same as Q-value?

Yes. In nuclear decay, the released energy is commonly called the Q-value.