The history of atomic theory began in 600 BC when Thales discovered static electricity, and Democritus proposed the idea of atoms. In the 1800s, Dalton performed experiments leading to his atomic theory. In the late 1800s and early 1900s, discoveries were made about the electron and structure of the atom, including the nucleus. Elements are made of only one type of atom, while compounds contain different types of atoms joined together. Atoms are the smallest particle that can participate in chemical reactions.

1. Resumen de Science
History of the Atom
600BC: Thales of Miletus discovered that a piece of amber, after
rubbing it with fur attracts bots of hair and feathers and other
light objects.
460BC: A Greek philosopher Democritus, develop the idea of atoms.
1800: John Dalton performed experiments with various chemicals.
1897: The English physicist J.J. Thompson discovered the electron
and proposed a model for the structure of the atom.
1911: Ernest Rutherord experiment.(investigate the inside of the
atom).
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2. 1919: Rutherford model. Finally he identify the particles of the nucleus
as discrete positive charges of matter. When there was
something wrong in his model Niels Bohr came up with a
theory that said the electrons do not spiral into the nucleus and
came up with some rules for what does happen. The electron
can exist in only one of the orbits.
Characteristics of metals and non-metals
Metals
• They tend to be shiny
• They are malleable and ductile
• High melting points
• High densities
• Solids at room temperature (except Mercury)
• They conducts electricity
Non-Metals
• They are opaques
• They are dulls
• They are brittle solids
• Poors conductors of electricity (except Carbon)
• Low melting points
Substance name Metal or non-metal?
Iron Metal
Sulphur Non-metal
Zinc Metal
Sodium Metal
Mercury Metal
Carbon Non-metal
Iodine Non-metal
Copper Metal
Atoms
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3. An atom is the smallest unit of an element, consisting of a dense,
central, positively charged nucleus surrounded by a system of
electrons, equal in number to the number of uclear protons.
All matter is made of tiny particles called atoms.
Every atom consists of a nucleus, and a cloud of particles called
electrons whizz non-stop round the nucleus.
NUCLEUS
ELECTRON CLOUD
Elements
An element is a substance that is made of only one kind of atom.
Each
element has a symbol.
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4. Compunds
A compound contains atoms of different elements joined together.
The symbol of a compound is called it’s formula.
Differences
Atoms Elements Compounds
Is the smallest particle Is a substance which On the other hand is
that can take part in a cannot be spilt into defined as a pure
chemical change. two or more simpler substance consisting
They are extremely substance by any sort of similar type of
small. of chemical means. molecules which can
They are made up of be made up of
particles which can different elements.
either be atoms,
molecules or ions.
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