1. Homework # 3 1.Bohr’s Diagram WS (2 pages) 1

2. Aim # 3: How are electrons arranged in an atom? 2

3. Review Q. what is the atomic number? 3

4. Atomic Number Identifies the element Indicates the number of protons in the nucleus The atomic number of an element never changes 4

5. What is the mass number of sodium? 5

6. Mass number Protons + neutrons 6

7. What is the charge of the atom? The atom is neutral Why? 7

8. What is the charge of the nucleus? Why? 8

9. 1. ELECTRON CONFIGURATION Atomic Mass Principal Energy Level Chemical Symbol Atomic Number Electron Configuration 2-4 2 12.0111 C 6 2-4 9

10. Each electron in an atom has its own distinct amount of energy Electrons in the first energy level have the lowest potential energy because they are located closest to the nucleus 2. Principal Energy Levels (shells) 10

11. 1 2 3 4 5 6 7 PE INCREASES 11

12. 12 Where does the ball have more potential energy? 1 3 2 4

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14. 3. Principal Energy Levels (shells) Principal Energy Level (n) Number of electrons (2n 2 ) 12 28 318 432 14

15. 2n 2 Energy level 1 can have a maximum of 2e- 2(1) 2 = 2 Energy level 2 can have a maximum of 8e- 2(2) 2 = 8 Energy level 3 can have a maximum of 18 e- 2(3) 2 = 18 Energy level 4 can have a maximum of 32e- 2(4) 2 = 32 15

16. What indicates the Number 4? 39.0983 4 19 K 2-8-8-1 16 4 shells Period 4

17. 4. Valence Electrons 17 39.0983 19 K 2-8-8-1 Valence electrons are the electrons in the last shell.

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22. Chemistry Regents: August 2008 22

23. 1. In the wave-mechanical model of the atom, orbitals are regions of the most probable locations of (1) protons (2) positrons (3) neutrons (4) electrons 23

24. 2. Which phrase describes an atom? (1) a positively charged electron cloud surrounding a positively charged nucleus (2) a positively charged electron cloud surrounding a negatively charged nucleus (3) a negatively charged electron cloud surrounding a positively charged nucleus (4) a negatively charged electron cloud surrounding 24

25. 3. Which total mass is the smallest? (1) the mass of 2 electrons (2) the mass of 2 neutrons (3) the mass of 1 electron plus the mass of 1 proton (4) the mass of 1 neutron plus the mass of 1 electron 25

26. 11. Which property could be used to identify a compound in the laboratory? (1)mass (2)melting point (3) temperature (4) volume 26

27. 16. Which substance can not be decomposed by a chemical change? (1) AlCl 3 (2) H 2 O (3) HI (4) Cu 27

28. 17. Tetrachloromethane, CCl 4, is classified as a (1) compound because the atoms of the elements are combined in a fixed proportion (2) compound because the atoms of the elements are combined in a proportion that varies (3) mixture because the atoms of the elements are combined in a fixed proportion (4) mixture because the atoms of the elements are combined in a proportion that varies 28

29. 31 What is the total number of protons in an atom with the electron configuration 2-8-18-32-18-1? (1) 69 (2) 79 (3) 118 (4) 197 29

30. June 2008 30

31. 3. A proton has a charge that is opposite the charge of (1) an alpha particle (2) a neutron (3) an electron (4) a positron 31

32. 2. What is the total number of electrons in an atom of potassium? (1) 18 (2) 19 (3) 20 (4) 39 32

33. 4. Which conclusion was a direct result of the gold foil experiment? (1) An atom is mostly empty space with a dense, positively charged nucleus. (2) An atom is composed of at least three types of subatomic particles. (3) An electron has a positive charge and is located inside the nucleus. (4) An electron has 33

34. 5. Which statement identifies the element arsenic? (1) Arsenic has an atomic number of 33. (2) Arsenic has a melting point of 84 K. (3) An atom of arsenic in the ground state has eight valence electrons. (4) An atom of arsenic in the ground state has a radius of 146 pm. 34

35. 8. Which statement describes the composition of potassium chlorate, KClO 3 ? (1) The proportion by mass of elements combined in potassium chlorate is fixed. (2) The proportion by mass of elements combined in potassium chlorate varies. (3) Potassium chlorate is composed of four elements. (4) Potassium chlorate is composed of five elements. 35

36. 12. Two solid samples each contain sulfur, oxygen, and sodium, only. These samples have the same color, melting point, density, and reaction with an aqueous barium chloride solution. It can be concluded that the two samples are the same (1) compound (2) Element (3) mixture (4) solution 36

37. 15. Which substance can not be broken down by a chemical reaction? (1) ammonia (2) Argon (3) methane (4) water 37

38. 33. The diagram below represents the nucleus of an atom. What are the atomic number and mass number of this atom? (1) The atomic number is 9 and the mass number is 19. (2) The atomic number is 9 and the mass number is 20. (3) The atomic number is 11 and the mass number is 19. (4) The atomic number is 11 and the mass number is 20. 38

39. 1 Which subatomic particles are paired with their charges? (1) electron–positive, neutron–negative, proton–neutral (2) electron–negative, neutron–neutral, proton–positive (3) electron–negative, neutron–positive, proton–neutral (4) electron–neutral, neutron 39

40. 1 Compared to an electron, which particle has a charge that is equal in magnitude but opposite in sign? (1) an alpha particle (2) a beta particle (3) a neutron (4) a proton 40

41. 2 The mass of a proton is approximately equal to (1) 1 atomic mass unit (2) 12 atomic mass units (3) the mass of 1 mole of carbon atoms (4) the mass of 12 moles of electrons 41