A particular K meson has a quark structure \({\rm{\bar u}}\)s. State the charge on this meson.

The Feynman diagram shows the changes that occur during beta minus (β^–) decay.

Label the diagram by inserting the four missing particle symbols.

Carbon-14 (C-14) is a radioactive isotope which undergoes beta minus (β^–) decay to the stable isotope nitrogen-14 (N-14). Energy is released during this decay. Explain why the mass of a C-14 nucleus and the mass of a N-14 nucleus are slightly different even though they have the same nucleon number.

charge: –1«e» or negative or K⁻

Negative signs required.

correct symbols for both missing quarks

exchange particle and electron labelled W or W^– and e or e^–
Do not allow W⁺ or e⁺ or β⁺ Allow β or β^–

decay products include an electron that has mass
OR
products have energy that has a mass equivalent
OR
mass/mass defect/binding energy converted to mass/energy of decay products

 «so»

mass C-14 > mass N-14
OR
mass of n > mass of p
OR
mass of d > mass of u

Accept reference to “lighter” and “heavier” in mass.
Do not accept implied comparison, eg “C-14 has greater mass”. Comparison must be explicit as stated in scheme.