Summary of 3Part1 (English)

1-4: The Constituents of Nuclei, Summary

[The Constituents of Nuclei]

Up to the 1930s,

people had thought that

the atomic nucleus consists

of protons and

electrons.

For example, they considered

that the nitrogen 14 of

the atomic number Z = 7

consists of 14 protons and

7 electrons.

This idea appeared quite

plausible, but it was made

clear that it contained

serious difficulties

as explained on the

last page.

Just after

the discovery of the neutron

by Chadwick,

D. Ivanenko (Soviet Union)

and

W. K. Heisenberg

(Germany, 1901-76)

independently proposed

an idea that

"the atomic nucleus consists of protons and neutrons" (1932).

This was nothing else than

the first step of

Nuclear Physics.

Hereafter this idea has been

established;

namely, a nucleus of an atomic number

Z

is a composite many-particle system

consisting of

Z protons and

N neutrons.

Accordingly, for example,

the nitrogen 14 nucleus of

the atomic number 7

consists of 7 protons and

7 neutrons.

And we can easily understand that

there exist some nuclei (isotopes)

of the same atomic number Z

but different neutron numbers

N.

[The Nucleon]

The proton and the neutron

have almost the same mass.

Different is their electric charges.

Their currently accepted properties

are listed in the following Table.

From these properties,

Heisenberg and

E. P. Wigner (US, 1902-95)

thought that these two kinds

of particles are of two

different states

of the same particle,

called "nucleon" today.

We can therefore say,

in a word, that

the constituent of the atomic nucleus

is nucleon.

[Summary of Part 1]

Let us summarize

what we have learned

in Part 1.

(1)

After the success of

the Rutherford Model of the Nuclear Atom,

the existence of the atomic nucleus

was recognized for the first time.

(2)

The mass of the nucleus

is almost equal to that of

the whole atom.

Its diameter is about

,

which is extremely smaller

than the size of the whole atom, about .

(3)

Due to the discovery of

the neutron by Chadwick,

it was clarified that

the constituents of nuclei

are protons

and neutrons

(generically nucleons).

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