SECTION SUMMARY
4.2 Structure of the Nuclear Atom Summary:
Three types of subatomic particles are electrons, protons, and neutrons. Electrons are
negatively charged subatomic particles, and they reside outside the nucleus. The
nucleus is the positive central core of an atom, which is composed of protons and
neutrons. Protons are subatomic particles that are positively charged and reside
inside the nucleus. Neutrons have no electrical charge, and they also reside inside the
nucleus.
J.J. Thomson discovered electrons in 1897 using the cathode ray. Cathode ray is the
stream of electrons produced at the negative electrode of a tube containing a gas at
low pressure.
In the nuclear atom, the protons and neutrons are located in the nucleus. The
electrons are distributed around the nucleus and occupy almost all the volume of the
atom.
Rutherford’s model of an atom explains well the location of protons, neutrons, and
electrons with respect to the nucleus. Atoms are mostly empty space. The subatomic
particles protons and neutrons are concentrated in the nucleus. Electrons are outside
of the nucleus. Most alpha particles that are positively charges pass through the
empty space without deflection. Few alpha particles come near to the nucleus are
deflected or bounce straight back.
4.2 Structure of the Nuclear Atom Vocabulary Terms:
Electrons:
negatively charged subatomic particles, residing
outside the nucleus.
Cathode ray:
is the stream of electrons produced at the negative
electrode of a tube containing a gas at low pressure.
Protons:
subatomic particles that are positively charged and
reside inside the nucleus
Neutrons:
subatomic particles with no electrical charge and
reside inside the nucleus
Nucleus:
the positive central core of an atom, which is
composed of protons and neutrons
The End of the Summary