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Essential Qu
estions: How
and why ha
Atomic Theo
s the ry changed over time? Atoms
0  Matter is anything that takes up space and has mass. All matter is made of atoms. 0  Atoms are the basic building blocks of matter. They make up everything around us; Your desk, the board, your body, everything is made of atoms! 0  Atoms are too small to see without powerful microscopes. Structure of the Atom
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Atomic Components
•  An element is matter that is composed of one
type of atom, which is the smallest piece of
matter that still retains the property of the
element.
•  Atoms are composed of particles called
protons, neutrons, and electrons.
Atomic Structure
There are two basic components in every atom: Electron Cloud Nucleus Subatomic Particles
Three subatomic particles make up every atom: Subatomic Particle Charge Location Proton Positive (+) Nucleus or “Core” Neutron No Charge (0) Nucleus or “Core” Electron Negative (-­‐) Electron Cloud, Outside of Nucleus Subatomic Particles
Electron Cloud: •  Electrons orbit the nucleus. Nucleus or “Core”: •  Protons and Neutrons are found in the nucleus. Atomic T
heory Changes over time…
Atomic Theory
0  Because we can not see atoms, we use models to teach and learn about atoms. 0  The atomic theory has changed over time as new technologies have become available. 0 Remember: ScientiPic knowledge builds on past research and experimentation. Atomic Theory Timeline
Scientist John Dalton Information All matter is made of atoms. Atoms are too small to see, indivisible and indestructible. All atoms of a given element are identical. Model Atomic Theory Timeline
Scientist J.J Thomson Information Discovered the negative electron, and predicted that there also must be a something positive to hold the electrons in place. Model Atomic Theory Timeline
Scientist Information Ernest Discovered the nucleus of Rutherford an atom and named the positive particles in the nucleus “protons”. Concluded that electrons are scattered in empty space around the nucleus. Model electrons protons Atomic Theory Timeline
Scientist Niels Bohr Information Concluded that electrons are located in planet-­‐like orbits around the nucleus in certain energy levels. Model Scientist (Many Scientists!) Information Electrons do not orbit the The Modern nucleus in neat planet-­‐like Atomic Theory orbits but move at high speeds in an electron cloud around the nucleus. Model Structure of the Atom
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Atomic Components
•  Protons and neutrons are found in a small positively
charged center of the atom called the nucleus that is
surrounded by a cloud containing electrons.
•  Protons are particles with an electrical charge of 1+.
Structure of the Atom
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Atomic Components
•  Electrons are particles with an electrical charge of 1–.
•  Neutrons are neutral particles that do not have an electrical charge.
Structure of the Atom
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Quarks—Even Smaller Particles
•  Protons and neutrons are made up of smaller particles called quarks.