Atoms

1. Atoms Preview • Understanding Concepts • Reading Skills • Interpreting Graphics

2. Understanding Concepts • When electricity is connected to a neon sign, an atom of neon inside the sign emits a photon. What has happened within the atom to allow the emission of light energy? A. An electron has moved to a lower energy level. B. Two electron orbitals have collided. C. A proton has been lost from the nucleus. D. The atom has gained a positive charge.

3. Understanding Concepts • When electricity is connected to a neon sign, an atom of neon inside the sign emits a photon. What has happened within the atom to allow the emission of light energy? A. An electron has moved to a lower energy level. B. Two electron orbitals have collided. C. A proton has been lost from the nucleus. D. The atom has gained a positive charge.

4. Understanding Concepts, continued 2. After a single subatomic particle is removed from an atom of helium, the helium atom becomes an atom of hydrogen. What subatomic particle was removed? F. an electron H. a quark G. a proton I. a neutron

5. Understanding Concepts, continued 2. After a single subatomic particle is removed from an atom of helium, the helium atom becomes an atom of hydrogen. What subatomic particle was removed? F. an electron H. a quark G. a proton I. a neutron

6. Understanding Concepts, continued 3. Gold has an average atomic mass of 196.97 u. Approximately how many atoms of gold are there in 100 g of gold? Note: there are 6.022 × 1023 atoms in a mole. A. 3.0573 × 1019 C. 1.1862 × 1024 B. 3.0573 × 1023 D. 1.1862 × 1028

7. Understanding Concepts, continued 3. Gold has an average atomic mass of 196.97 u. Approximately how many atoms of gold are there in 100 g of gold? Note: there are 6.022 × 1023 atoms in a mole. A. 3.0573 × 1019 C. 1.1862 × 1024 B. 3.0573 × 1023 D. 1.1862 × 1028

8. Understanding Concepts, continued 4. What subatomic particles can be found in regions called orbitals? F. protons H. electrons G. neutrons I. photons

9. Understanding Concepts, continued 4. What subatomic particles can be found in regions called orbitals? F. protons H. electrons G. neutrons I. photons

10. Understanding Concepts, continued 5. Xenon has an atomic number of 54. A particular isotope of xenon has a mass number of 131. How many protons and how many neutrons does each atom of that isotope have?

11. Understanding Concepts, continued • Xenon has an atomic number of 54. A particular isotope of xenon has a mass number of 131. How many protons and how many neutrons does each atom of that isotope have? Answer: 54 protons and 77 neutrons

12. Understanding Concepts, continued 6. Suppose that a team of chemists discovered that lead has the following composition: 80% of lead is an isotope whose mass number is 207, and 20% of lead is an isotope whose mass number is 208. What would they determine the average atomic mass of lead to be?

13. Understanding Concepts, continued • Suppose that a team of chemists discovered that lead has the following composition: 80% of lead is an isotope whose mass number is 207, and 20% of lead is an isotope whose mass number is 208. What would they determine the average atomic mass of lead to be? Answer: 207.2 u

14. Reading Skills THE BOHR MODEL OF THE ATOM In the Bohr model of the atom, electrons can be found only in certain energy levels. Electrons “jump” directly from one level to the next level; they are never found between levels. When an electron moves from one level to another, it gains or loses energy, depending on the direction of its jump.

15. Reading Skills, continued 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. If this light is passed through a prism, a pattern of lines appears. Each line has 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.

16. Reading Skills, continued • In the Bohr model of the atom, which of the following characteristics of electrons is limited? A. the number of electrons in an atom B. the location of the electrons C. the size of electrons D. the speed of electrons

17. Reading Skills, continued • In the Bohr model of the atom, which of the following characteristics of electrons is limited? A. the number of electrons in an atom B. the location of the electrons C. the size of electrons D. the speed of electrons

18. Reading Skills, continued 8. 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 G. electrons changing color H. atoms of the gas exchanging electrons I. There is not enough information to determine the answer.

19. Reading Skills, continued 8. 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 G. electrons changing color H. atoms of the gas exchanging electrons I. There is not enough information to determine the answer.

20. Interpreting Graphics The graphic below shows how electron orbitals around the nucleus of an atom are organized into energy levels. Each orbital holds 2 electrons. Use this graphic to answer questions 9–11.

21. Interpreting Graphics, continued 9. If every orbital of an atom’s n = 4 energy level was full of electrons, how many electrons would there be in that energy level? A. 7 C. 16 B. 14 D. 32

22. Interpreting Graphics, continued 9. If every orbital of an atom’s n = 4 energy level was full of electrons, how many electrons would there be in that energy level? A. 7 C. 16 B. 14 D. 32

23. Interpreting Graphics, continued 10. The atomic number of sulfur is 16. If energy levels are filled with electrons from the innermost level to the outermost level, how many electrons are in the n = 3 energy level of a neutral sulfur atom?

24. Interpreting Graphics, continued 10. The atomic number of sulfur is 16. If energy levels are filled with electrons from the innermost level to the outermost level, how many electrons are in the n = 3 energy level of a neutral sulfur atom? Answer: 6 electrons

25. Interpreting Graphics, continued 11. Every known element has seven or fewer energy levels. How many orbitals would there be room for in energy level n = 7?

26. Interpreting Graphics, continued 11. Every known element has seven or fewer energy levels. How many orbitals would there be room for in energy level n = 7? Answer: 49 orbitals

27. Interpreting Graphics, continued The table below gives information about the subatomic particles in six atoms. Use this table to answer questions 12–13.

28. Interpreting Graphics, continued 12. Which two atoms are isotopes of the same element? F. #1 and #2 H. #3 and #4 G. #2 and #3 I. #4 and #5

29. Interpreting Graphics, continued 12. Which two atoms are isotopes of the same element? F. #1 and #2 H. #3 and #4 G. #2 and #3 I. #4 and #5

30. Interpreting Graphics, continued 13.What is the mass of one mole of the heaviest atom in the table?

31. Interpreting Graphics, continued • What is the mass of one mole of the heaviest atom in the table? Answer: 94 grams