U2L4 - The Atom
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Transcript of U2L4 - The Atom
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Unit 2 Lesson 4 The Atom
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Unit 2 Lesson 4 The Atom
Indiana Standards
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• 8.1.1 Explain that all matter is composed of particular arrangements of atoms of approximately one hundred elements.
• 8.1.6 Describe the structure of an atom and relate the arrangement of electrons to how that atom interacts with other atoms.
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As a Matter of Fact …
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What is matter made of?
• The Greek philosopher Democritus thought matter could be divided into smaller and smaller units he called atomos.
• In 1803, John Dalton proposed that all substances are made of atoms that cannot be divided.
Unit 2 Lesson 4 The Atom
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What is matter made of?
• In 1897, J. J. Thomson performed experiments that detected smaller particles within atoms.
• In the early 1900s, Ernest Rutherford and James Chadwick revealed the nature of the dense center of an atom.
• Today we have the electron cloud model.
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Unit 2 Lesson 4 The Atom
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What are atoms?
• An atom is the smallest particle into which an element can be divided and still be the same substance.
• In 1808, John Dalton published an atomic theory that said all atoms of a particular element are identical.
• Dalton also said that atoms of an element differ from atoms of other elements.
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Unit 2 Lesson 4 The Atom
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Up and Atom!
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What are the parts of an atom?
• Atoms are made of protons, neutrons, and electrons.
• Protons are positively charged particles.
• The mass of a proton is given in the atomic mass unit (u). One proton has a mass of 1 u.
Unit 2 Lesson 4 The Atom
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What are the parts of an atom?
• Neutrons are particles that have no electrical charge.
• In most atoms, there are at least as many neutrons as protons.
• The mass of a neutron is slightly more than a proton but is still considered to be 1 u.
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What are the parts of an atom?
• The nucleus is the at the center of the atom and contains the protons and neutrons.
• The overall charge of the nucleus is equal to the number of protons in the nucleus.
• The nucleus is small but very dense.
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What are the parts of an atom?
• Electrons are negatively charged particles.
• Electrons move around the nucleus very quickly in a region called the electron cloud.
• Electrons are very small compared to protons and neutrons.
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What are the parts of an atom?
• Why is the exact location of an electron hard to identify?
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What are the parts of an atom?
• The number of protons and electrons in an atom are the same, so the charges are balanced.
• An atom can gain or lose electrons to become an ion, which has a net positive or negative charge.
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Take a Number!
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How can we describe atoms?
• Different combinations of protons, neutrons, and electrons produce atoms with different properties.
• The number of each kind of particle within an atom determines its unique properties.
Unit 2 Lesson 4 The Atom
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How can we describe atoms?
• The number of protons distinguishes the atoms of one element from the atoms of another.
• The number of protons in the nucleus of an atom is the atomic number of that atom.
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Unit 2 Lesson 4 The Atom
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How can we describe atoms?
• Atoms of an element have the same number of protons, but the number of neutrons may differ.
• Isotopes are atoms of the same element that have different numbers of neutrons.
• The total number of protons and neutrons in an atom’s nucleus is its mass number.
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Unit 2 Lesson 4 The Atom