2 Particles as Building Blocks of Matter
9
electrically neutral. Those were identified more than two decades later and
called neutrons (see below).
Ernest Rutherford was a New Zealand-born physicist who pioneered the
Rutherford model of the atom, which posits that the mass of an atom is
concentrated in the center of the nucleus. Thus was born the basic picture of
the atom and its nucleus, which persists today. He is rightly called the father of
nuclear physics. Born in the year 1871 in rural Brightwater in New Zealand’s
south island, he learned to invent new ways to keep himself occupied in the
midst of the limited means of his parents. His mother was a school teacher who
believed that knowledge was power, and his father, a hard working flax-miller.
At age 19, he was awarded a scholarship to attend the Canterbury College
in Christ Church, New Zealand. By age 24, he was already in Cambridge
where he worked with such giants of the field of physics as Sir J. J. Thompson
studying X-rays. X-rays were discovered only months before, by Wilhelm
Conrad Rontzen. Working independently when Thompson was working on
the electron, Rutherford discovered what he called the “alpha” and “beta"
radiation. The latter consists of electron, a basic constituent building block
of matter, and the former is the nucleus of the helium atom. The alpha
radiation was used in the famous “gold foil experiment” by Rutherford to
establish that inside each atom there was small volume where most of the
atom’s mass was concentrated. A clearer picture of the constituents of the atom
was emerging. Soon after, Rutherford moved from England to Canada and
then to the University of Manchester after that. On 7 March, 1911, Rutherford
attended a meeting of the Manchester Literary and Philosophical Society,
where he announced the discovery of the atomic nucleus. The American
Physical Society has decided to mark this date as the beginning of a century of
elementary particle physics [102].
At Manchester, Rutherford continued studying the atomic nucleus and
established that the entire mass of the atom was concentrated in the nucleus.
He showed this by hitting the atom with alpha particles, which bounced
back as if there was a solid object at the center of the target. This led to the
Rutherford model of the atom which replaced the so-called plum pudding
model of the atom proposed by his one time mentor J. J. Thompson. The plum
pudding model, as the name suggests, said that the atom was like a pudding
and the electrons and protons were embedded in it at random.
Works of pioneers like Rutherford and Thompson were giving a clearer
picture of the atom but a lot remained to be discovered in the early 1900s.
More details of Dalton’s atomic conjecture of 1803 were coming into shape.
Dalton made several prophetic conjectures about the atom and its role. They
were:
9
electrically neutral. Those were identified more than two decades later and
called neutrons (see below).
Ernest Rutherford was a New Zealand-born physicist who pioneered the
Rutherford model of the atom, which posits that the mass of an atom is
concentrated in the center of the nucleus. Thus was born the basic picture of
the atom and its nucleus, which persists today. He is rightly called the father of
nuclear physics. Born in the year 1871 in rural Brightwater in New Zealand’s
south island, he learned to invent new ways to keep himself occupied in the
midst of the limited means of his parents. His mother was a school teacher who
believed that knowledge was power, and his father, a hard working flax-miller.
At age 19, he was awarded a scholarship to attend the Canterbury College
in Christ Church, New Zealand. By age 24, he was already in Cambridge
where he worked with such giants of the field of physics as Sir J. J. Thompson
studying X-rays. X-rays were discovered only months before, by Wilhelm
Conrad Rontzen. Working independently when Thompson was working on
the electron, Rutherford discovered what he called the “alpha” and “beta"
radiation. The latter consists of electron, a basic constituent building block
of matter, and the former is the nucleus of the helium atom. The alpha
radiation was used in the famous “gold foil experiment” by Rutherford to
establish that inside each atom there was small volume where most of the
atom’s mass was concentrated. A clearer picture of the constituents of the atom
was emerging. Soon after, Rutherford moved from England to Canada and
then to the University of Manchester after that. On 7 March, 1911, Rutherford
attended a meeting of the Manchester Literary and Philosophical Society,
where he announced the discovery of the atomic nucleus. The American
Physical Society has decided to mark this date as the beginning of a century of
elementary particle physics [102].
At Manchester, Rutherford continued studying the atomic nucleus and
established that the entire mass of the atom was concentrated in the nucleus.
He showed this by hitting the atom with alpha particles, which bounced
back as if there was a solid object at the center of the target. This led to the
Rutherford model of the atom which replaced the so-called plum pudding
model of the atom proposed by his one time mentor J. J. Thompson. The plum
pudding model, as the name suggests, said that the atom was like a pudding
and the electrons and protons were embedded in it at random.
Works of pioneers like Rutherford and Thompson were giving a clearer
picture of the atom but a lot remained to be discovered in the early 1900s.
More details of Dalton’s atomic conjecture of 1803 were coming into shape.
Dalton made several prophetic conjectures about the atom and its role. They
were: