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2
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3
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- Protons are positively charged particles found in the atomic nucleus.
Protons were discovered by Ernest Rutherford..
- Experiments done in the late 1960's and early 1970's showed that protons
are made from other particles called quarks. Protons are made from two
'up' quarks and one 'down' quark.
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13
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- Neutrons are uncharged particles found in the atomic nucleus. Neutrons
were discovered by James Chadwick in 1932.
- Experiments done in the late 1960's and early 1970's showed that
neutrons are made from other particles called quarks. Neutrons are made
from one 'up' quark and two 'down' quarks.
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15
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- Electrons are negatively charged particles that surround the atom's
nucleus. Electrons were discovered by J. J. Thomson in 1897.
- Electrons determine properties of the atom. Chemical reactions involve
sharing or exchanging electrons.
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- The nucleus is the central part of an atom. It is composed of protons
and neutrons.
- The nucleus contains most of an atom's mass.
- It was discovered by Ernest Rutherford in 1911.
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- Believed to be one of the basic building blocks of matter. Quarks were
first discovered in experiments done in the late 1960's and early
1970's.
- Three families of quarks are known to exist. Each family contains two
quarks. The first family consists of Up and Down quarks, the quarks that
join together to form protons and neutrons.
- The second family consists of Strange and Charm quarks and only exist at
high energies.
- The third family consists of Top and Bottom quarks and only exist at
very high energies.
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- Atoms that have the same number of protons but different numbers of
neutrons
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- Model of the atom pictures the electrons moving around the nucleus in a
region called an electron cloud.
- The electron cloud is a cloud of varying density surrounding the
nucleus. The varying density shows where an electron is more or less
likely to be. Atoms with electrons in higher energy levels have
additional electron clouds of different shapes that also show where
those electrons are likely to be.
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26
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Notes
