Scribd
Upload
7 views1 page

The Nucleus

The nucleus consists of protons and neutrons, collectively known as nucleons, with protons carrying a positive charge and neutrons being electrically neutral. Protons are significantly heavier than electrons, and their number in an atom balances the negative charge of electrons to maintain electrical neutrality. The discovery of the neutron by James Chadwick in 1932 explained the additional mass in atomic nuclei and confirmed the existence of quarks as the smaller building blocks of protons and neutrons.

Uploaded by

Nwoko chuks
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
7 views1 page

The Nucleus

The nucleus consists of protons and neutrons, collectively known as nucleons, with protons carrying a positive charge and neutrons being electrically neutral. Protons are significantly heavier than electrons, and their number in an atom balances the negative charge of electrons to maintain electrical neutrality. The discovery of the neutron by James Chadwick in 1932 explained the additional mass in atomic nuclei and confirmed the existence of quarks as the smaller building blocks of protons and neutrons.

Uploaded by

Nwoko chuks
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
You are on page 1/ 1

Unlike the electron, the nucleus can be broken up into smaller building blocks called protons and

neutrons. Together, the protons and neutrons are called nucleons.

Each proton carries one unit of positive electric charge. Since we know that atoms are electrically
neutral, i.e. do not carry any extra charge, then the number of protons in an atom has to be the same as
the number of electrons to balance out the positive and negative charge to zero. The total positive
charge of a nucleus is equal to the number of protons in the nucleus. The proton is much heavier than
the electron (10 000 times heavier!) and has a mass of 1.6726 x 10−27 kg.

When we talk about the atomic mass of an atom, we are mostly referring to the combined mass of the
protons and neutrons, i.e. the nucleons. The neutron is electrically neutral i.e. it carries no charge at all.
Like the proton, it is much heavier than the electron and its mass is 1.6749 x 10 −27 kg (slightly heavier
than the proton).

Rutherford predicted (in 1920) that another kind of particle must be present in the nucleus along with
the proton. He predicted this because if there were only positively charged protons in the nucleus, then
it should break into bits because of the repulsive forces between the like-charged protons! Also, if
protons were the only particles in the nucleus, then a helium nucleus (atomic number 2) would have
two protons and therefore only twice the mass of hydrogen. However, it is actually four times heavier
than hydrogen. This suggested that there must be something else inside the nucleus as well as the
protons. To make sure that the atom stays electrically neutral, this particle would have to be neutral
itself. In 1932 James Chadwick discovered the neutron and measured its mass.

Unlike the electron which is thought to be a point particle and unable to be broken up into smaller
pieces, the proton and neutron can be divided. Protons and neutrons are built up of smaller particles
called quarks. The proton and neutron are made up of 3 quarks each.

You might also like