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 & Antiquarks

Quark Flavours and Their Charges

Think of quarks as the building blocks of protons and neutrons, each with a unique “flavour” that determines its electric charge. Their charges are expressed as fractions of the elementary charge \(e\). The table below shows each flavour, its charge, and the opposite charge of its corresponding antiquark.

FlavourChargeAntiquark Charge
Up (u)\$+2/3\,e\$\$-2/3\,e\$
Down (d)\$-1/3\,e\$\$+1/3\,e\$
Strange (s)\$-1/3\,e\$\$+1/3\,e\$
Charm (c)\$+2/3\,e\$\$-2/3\,e\$
Bottom (b)\$-1/3\,e\$\$+1/3\,e\$
Top (t)\$+2/3\,e\$\$-2/3\,e\$

Analogy: The Quark Team ⚛️

Imagine each quark flavour as a superhero in a team. The charge is like their special power level:

  • 🦸‍♂️ Up and Charm have a high power level of \$+2/3\$.

  • 🦸‍♀️ Down, Strange, and Bottom have a lower power level of \$-1/3\$.

  • 🦸‍♂️ Top also has the high power \$+2/3\$.

When a superhero turns into an antiquark, their power level flips sign, just like a superhero changing costumes to the opposite colour.

Exam Tip: Quick Recall Trick

Rule of Thumb: Quarks with an “up‑type” name (up, charm, top) carry a charge of \$+2/3\$, while the “down‑type” names (down, strange, bottom) carry \$-1/3\$. The antiquark simply reverses the sign.

Use the mnemonic: “Up, Charm, Top = +2/3; Down, Strange, Bottom = -1/3” to remember quickly.

Practice Steps

  1. Identify the quark flavour.

  2. Write down its charge using the rule of thumb.

  3. Write the antiquark charge by flipping the sign.

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Remember: The antiquark’s charge is always the opposite of its quark partner.