Transcript The Atom
Unit 2 Lesson 6 The Atom Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom Florida Benchmarks • SC.8.P.8.7 Explore the scientific theory of atoms (also known as atomic theory) by recognizing that atoms are the smallest unit of an element and are composed of subatomic particles (electrons surrounding a nucleus containing protons and neutrons). • LA.6.2.2.3 The student will organize information to show understanding (e.g., representing main ideas within text through charting, mapping, paraphrasing, summarizing, or comparing/contrasting). Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom As a Matter of Fact … 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom Up and Atom! 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom What are the parts of an atom? • Why is the exact location of an electron are hard to identify? Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom Take a Number! 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom 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. Copyright © Houghton Mifflin Harcourt Publishing Company Unit 2 Lesson 6 The Atom How can we describe atoms? • Atoms of an element have the same number of protons, but the number of neutron 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. Copyright © Houghton Mifflin Harcourt Publishing Company