Given the large number of subatomic particles that were discovered using collisions and particle accelerators, it wasn't long before scientists suggested that a large number of these particles were, in turn, built from just three smaller particles called quarks .   The first quark is called an "up" quark and has a charge of e.  The second quark is called a "down" quark and has a charge of e.  The third particle is called the "strange" quark and has a charge of e.  Using the powerful Stanford Linear Accelerator, scientists discovered that the mass and charge of a proton are indeed concentrated in three regions within the particle, supporting the quark model.

Protons and neutrons are each composed of three quarks.

 

The up and down quarks are first-generation quarks.  Subsequent research and theory has identified four other quarks named strange, charm, beauty, and truth.        


Quark: a fundamental particle in the hadron family 

 

Read
Review "Table 17.5: Some Properties of Quarks" on page 846 of the textbook.  The table summarizes first-, second-, and third-generation quarks.

The quark model and weak electric force help explain nuclear changes, like beta and beta-positive decay.  For example, during the decay process a down quark can change into an up quark, leading to the emission of an electron and an electron antineutrino.  The following illustration shows the equation and graphical representation of this process showing the conservation of mass and charge.

Beta Decay

 

 

 

Beta Positive Decay