Chemistry U13 - Nuclear Stability

Nucleaon

Protons (P+) and Neutrons (N=)

Nuclide

SPECIFIC NUCLEUS, written as Isotope name or Nuclear symbol

EX: Magnesium - 24 or ^24₁₂MG

Strong Force

HOLD NUCLEUS TOGETHER

Acts BETWEEN nucleons which are Very close together, if nucleons too far apart REPULSION FORCES are LARGER THAN STRONG FORCE and Nucleus will fall apart

Binding Energy

Energy released when nucleons make a NUCLIDE

Energy comes from conversion of mass to energy

**A LARGER MASS DEFECT means MORE BINDING ENERGY RELEASED and thus A MORE STABLE NUCLIDE

Mass defect

The difference in Mass

**A LARGER MASS DEFECT means MORE BINDING ENERGY RELEASED and thus A MORE STABLE NUCLIDE

Bands of stability

Plots (P+) vs (N=)

Shows STABLE ISOTOPES falling in a narrow band

Nuclear stability

Finding the N/Z RATIO

WHERE N = # Neutrons, Z = # Protons

Small atoms

Atomic number 20 AND UNDER,

RATIOS ARE 1:1

Large atoms

Atomic numbers 20 AND OVER

RATIOS ARE 1:5:1

More NEUTRONS ARE NEEDED between the protons

Magic Numbers

Nuclei with magic numbers of Protons, neutrons or nucleons are STABLE

Number of nuclear represent COMPLETED NUCLEAR ENERGY LEVELS ARE MAGIC NUMBERS

MN examples

2, 8, 20, 28, 50, 82, and 126

Radioactive Decay

When an Isotope is NOT STABLE

Spontaneous change from unstable nuclei to a more stable one, releases particles EM waves or both

**ALWAYS TRANSITIONS FROM UNSTABLE TO MORE STABLE

Alpha decay

Large N/Z ratio, Emits an alpha particle

HELIM ATOM -2 (P+), 2 (N=) ⁴₂HE

Atomic number DECREASES BY 2

Mass number DECREASES BY 4

Beta decay

Usually with large N/Z number

Neutron breaks apart into PROTON AND BETA PARTICAL (basically an electron) ⁰_-1e

Atomic number INCREASES BY 1

Mass number STAYS THE SAME

Electron capture

Nucleus has TOO MANY PROTONS, E- combines with Proton to make a NEUTRON AND GAMMA RAY which are given off

Atomic number DECREASES BY 1

Mass number STAYS THE SAME

EX: ⁵¹₂₄CR + ⁰_-1E - - - - - - - - > ⁵¹₂₃V + γ

Positron emission

If TOO MANY PROTONS, Positron leaves the nucleus usually hitting an E-, it’s antiparticle. When hit they undergo annihilation of matter EMITTING GAMMA RAYS

Atomic number DECREASES BY 1

Mass number STAYS THE SAME

EX: ____ + ⁰₊₁E - - - - - - - - > ___ + 2γ