recall and use the charge of each flavour of quark and understand that its respective antiquark has the opposite charge (no knowledge of any other properties of quarks is required)

Fundamental Particles – Quarks and Their Charges

In the Standard Model of particle physics, matter is built from a small set of elementary particles called quarks. There are six different flavours of quark. For the purpose of this topic you only need to know the electric charge of each flavour and that the corresponding antiquark carries the opposite charge.

Quark Flavours and Their Charges

Antiquarks – Opposite Charges

Each quark has a corresponding antiquark. The antiquark has the same magnitude of charge but opposite sign.

Key Points to Remember

• Quarks come in six flavours: up, down, charm, strange, top, bottom.
• Charges are either \$+\frac{2}{3}\,e\$ or \$-\frac{1}{3}\,e\$.
• Antiquarks have the same magnitude of charge but opposite sign.
• Only the charge is required for this objective; other properties (colour, spin, mass) are not needed.

Worked Example

Determine the total electric charge of the combination \$u\bar{d}s\$.

1. Write the charge of each constituent:

   • \$u\$: \$+\frac{2}{3}\,e\$
   • \$\bar{d}\$: \$+\frac{1}{3}\,e\$ (opposite of \$d\$)
   • \$s\$: \$-\frac{1}{3}\,e\$

2. Add the charges:

   \$\frac{2}{3}e + \frac{1}{3}e - \frac{1}{3}e = \frac{2}{3}e\$

3. Result: the combination carries a net charge of \$+\frac{2}{3}\,e\$.

Practice Questions

1. What is the charge of an anti‑charm quark?
2. List the charges of the three quarks that make up a proton (you may use the known composition \$uud\$).
3. If a particle is composed of \$c\bar{s}b\$, what is its total charge?
4. True or false: the anti‑top quark has a charge of \$+\frac{2}{3}\,e\$.