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Section 2 The Atom

Section 2 The Atom. Chapter 11. What Is an Atom Made Of?. The Nucleus Protons are positively charged particles Neutrons are the particles of the nucleus that have no electrical charge.

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Section 2 The Atom

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  1. Section2 The Atom Chapter 11 What Is an Atom Made Of? • The NucleusProtons are positively charged particles • Neutrons are the particles of the nucleus that have no electrical charge. • Electrons are the negatively charged particles in atoms. Electrons are found around the nucleus within electron clouds.

  2. Section2 The Atom Chapter 11

  3. Section1 Development of the Atomic Theory Chapter 11 Where Are the Electrons? • Rutherford proposed that in the center of the atom is a tiny, positively charged part called the nucleus. • In 1913, Niels Bohr proposed that electrons move around the nucleus in certain paths, or energy levels.

  4. Section1 Development of the Atomic Theory Chapter 11 Where Are the Electrons?, continued • The Modern Atomic Theorythere are regions inside the atom where electrons are likely to found. These regions are called electron clouds.

  5. Section2 The Atom Chapter 11 How Do Atoms of Different Elements Differ? • Starting SimplyThe hydrogen atom has one proton and one electron. • Now for Some NeutronsThe helium atom has two protons, two neutrons, and two electrons.

  6. Section2 The Atom Chapter 11 Protons and Atomic number • The number of protons in the nucleus = the atomic number • All atoms of an element have the same atomic number.

  7. Section2 The Atom Chapter 11 Isotopes • Isotopesare atoms that have the same number of protons but have different numbers of neutrons.

  8. Section2 The Atom Chapter 11 Isotopes, continued • Properties of IsotopesAn unstable atom is an atom with a nucleus that will change over time. This type of isotope is radioactive. • Telling Isotopes ApartYou can identify each isotope of an element by its mass number. The mass number is the sum of the protons and neutrons in an atom.

  9. Section2 The Atom Chapter 11 Isotopes, continued

  10. Section2 The Atom Chapter 11 Isotopes, continued • Naming IsotopesTo identify a specific isotope of an element, write the name of the element followed by a hyphen and the mass number of the isotope. • Calculating the Mass of an ElementThe atomic mass of an element is the weighted average of the masses of all the naturally occurring isotopes of that element.

  11. Section2 The Atom Chapter 11

  12. Section2 The Atom Chapter 11 Forces in Atoms • Four Basic ForcesFour basic forces are at work everywhere, even within the atom. These forces are gravitational force, electromagnetic force, strong force, and weak force. • These forces work together to give an atom its structure and properties.

  13. Section2 The Atom Chapter 11

  14. Introduction to Atoms Chapter 11 Concept Map Use the terms below to complete the concept map on the next slide.

  15. Introduction to Atoms Chapter 11

  16. Introduction to Atoms Chapter 11

  17. Standardized Test Preparation Chapter 11 Passage 1In the Bohr model of the atom, electrons can be found only in certain energy levels. Electrons “jump” from one level to the next level without passing through any of the regions in between. When an electron moves from one level to another, it gains or loses energy, depending on the direction of its jump. Bohr’s model explained an unusual event. When electric charges pass through atoms of a gaseous element, the gas produces a glowing light, like in a neon sign. Continued on the next slide

  18. Standardized Test Preparation Chapter 11 Passage 1, continuedIf this light is passed through a prism, a pattern of lines appears, each line having a different color. The pattern depends on the element—neon has one pattern, and helium has another. In Bohr’s model, the lines are caused by electron jumps from higher to lower energy levels. Because only certain jumps are possible, electrons release energy only in certain quantities. These “packets” of energy produce the lines that are seen.

  19. Standardized Test Preparation Chapter 11 1. In the Bohr model of the atom, what limitation is placed on electrons? A the number of electrons in an atom B the electrons’ being found only in certain energy levels C the size of electrons D the speed of electrons

  20. Standardized Test Preparation Chapter 11 1. In the Bohr model of the atom, what limitation is placed on electrons? A the number of electrons in an atom B the electrons’ being found only in certain energy levels C the size of electrons D the speed of electrons

  21. Standardized Test Preparation Chapter 11 2. What causes the colored lines that appear when the light from a gas is passed through a prism? Fpackets of energy released by electron jumps Gelectrons changing color Hatoms of the gas exchanging electrons IThere is not enough information to determine the answer.

  22. Standardized Test Preparation Chapter 11 2. What causes the colored lines that appear when the light from a gas is passed through a prism? F packets of energy released by electron jumps Gelectrons changing color Hatoms of the gas exchanging electrons IThere is not enough information to determine the answer.

  23. Standardized Test Preparation Chapter 11 Passage 2No one has ever seen a living dinosaur, but scientists have determined the appearance of Tyrannosaurus rex by studying fossilized skeletons. Scientists theorize that these extinct creatures had big hind legs, small front legs, a long, whip-like tail, and a mouth full of dagger-shaped teeth. However, theories of how T. rex walked have been harder to develop. For many years, most scientists thought that T. rex plodded slowly like a big, lazy lizard. Continued on the next slide

  24. Standardized Test Preparation Chapter 11 Passage 2, continuedHowever, after studying well-preserved dinosaur tracks and noticing skeletal similarities between certain dinosaur fossils and living creatures like the ostrich, many scientists now theorize that T. rex could turn on the speed. Some scientists estimate that T. rex had bursts of speed of 32 km/h (20 mi/h)!

  25. Standardized Test Preparation Chapter 11 1.According to this passage, where does most of what we know about the appearance of Tyrannosaurus rex come from? Afossilized skeletons Bdinosaur tracks Cliving organisms such as the ostrich Dliving specimens of T. rex

  26. Standardized Test Preparation Chapter 11 1.According to this passage, where does most of what we know about the appearance of Tyrannosaurus rex come from? A fossilized skeletons Bdinosaur tracks Cliving organisms such as the ostrich Dliving specimens of T. rex

  27. Chapter 11 Standardized Test Preparation 2. How did scientists conclude that T. rex could probably move very quickly? FThey measured the speed at which it could run. GThey compared fossilized T. rex tracks with T. rex skeletons. HThey studied dinosaur tracks and noted similarities between ostrich skeletons and T. rex skeletons. IThey measured the speed at which ostriches could run.

  28. Chapter 11 Standardized Test Preparation 2. How did scientists conclude that T. rex could probably move very quickly? FThey measured the speed at which it could run. GThey compared fossilized T. rex tracks with T. rex skeletons. H They studied dinosaur tracks and noted similarities between ostrich skeletons and T. rex skeletons. IThey measured the speed at which ostriches could run.

  29. Chapter 11 Standardized Test Preparation Interpreting Graphics Use the diagram of an atom below to answer the questions that follow.

  30. Chapter 11 Standardized Test Preparation 1. The black circles in the center of the model represent neutrons. What do the white circles in the center represent? Aelectrons Bprotons Cnuclei Datoms

  31. Chapter 11 Standardized Test Preparation 1. The black circles in the center of the model represent neutrons. What do the white circles in the center represent? Aelectrons Bprotons Cnuclei Datoms

  32. Standardized Test Preparation Chapter 11 2. What is the mass number of the atom shown in the model? F 3 G7 H9 I11

  33. Standardized Test Preparation Chapter 11 2. What is the mass number of the atom shown in the model? F 3 G 7 H9 I11

  34. Standardized Test Preparation Chapter 11 3. What is the overall charge of the atom shown in the model? A12 B11 C0 D21

  35. Standardized Test Preparation Chapter 11 3. What is the overall charge of the atom shown in the model? A12 B11 C0 D21

  36. Standardized Test Preparation Chapter 11 Math Read each question, and choose the best answer.

  37. Standardized Test Preparation Chapter 11 1. Aimee, Mari, and Brooke are 163 cm, 171 cm, and 175 cm tall. Which of the following measurements is a reasonable average height of these three friends? A170 cm B175 cm C255 cm D509 cm

  38. Standardized Test Preparation Chapter 11 1. Aimee, Mari, and Brooke are 163 cm, 171 cm, and 175 cm tall. Which of the following measurements is a reasonable average height of these three friends? A 170 cm B175 cm C255 cm D509 cm

  39. Standardized Test Preparation Chapter 11 2. A certain school has 40 classrooms. Most of the classrooms have 25 to 30 students. Which of the following is a reasonable estimate of the number of students that go to this school? F40 students G100 students H1,100 students I2,000 students

  40. Standardized Test Preparation Chapter 11 2. A certain school has 40 classrooms. Most of the classrooms have 25 to 30 students. Which of the following is a reasonable estimate of the number of students that go to this school? F40 students G100 students H 1,100 students I2,000 students

  41. Standardized Test Preparation Chapter 11 3. Jenna is setting up a fish tank in her room. The tank is the shape of a rectangular prism. The height of the tank is 38 cm, the width is 23 cm, and the length is 62 cm. The tank is filled with water to a point that is 7 cm from the top. How much water is in the tank? A44,206 cm3 B48,070 cm3 C54,188 cm3 D64,170 cm3

  42. Standardized Test Preparation Chapter 11 3. Jenna is setting up a fish tank in her room. The tank is the shape of a rectangular prism. The height of the tank is 38 cm, the width is 23 cm, and the length is 62 cm. The tank is filled with water to a point that is 7 cm from the top. How much water is in the tank? A 44,206 cm3 B48,070 cm3 C54,188 cm3 D64,170 cm3

  43. Standardized Test Preparation Chapter 11 4. Which of the following is equal to 85? F8  8  8  8  8 G5  5  5  5  5  5  5  5 H5  8 I8  8  8  8  8

  44. Standardized Test Preparation Chapter 11 4. Which of the following is equal to 85? F8  8  8  8  8 G5  5  5  5  5  5  5  5 H5  8 I 8  8  8  8  8

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