Ch 4 Arrangement of Electrons in atoms

1. Ch 4 Arrangement of Electrons in atoms

2. ELECTROMAGNETIC RADIATION • subatomic particles (electron, photon, etc) have both PARTICLE and WAVE properties • Light is electromagnetic radiation - crossed electric and magnetic waves: • Properties : • Wavelength, l (nm) • Frequency, n (s-1, Hz) • Amplitude, A • constant speed. c • 3.00 x 108 m.s-1

3. 7.1

5. Properties of Waves Wavelength (l) is the distance between identical points on successive waves. Amplitude is the vertical distance from the midline of a wave to the peak or trough. 7.1

6. Atomic Line Spectra • Bohr’s greatest contribution to science was in building a simple model of the atom. • It was based on understanding the SHARP LINE SPECTRA of excited atoms. Niels Bohr (1885-1962) (Nobel Prize, 1922)

7. H Hg Ne Line Spectra of Excited Atoms • Excited atoms emit light of only certain wavelengths • The wavelengths of emitted light depend on the element.

8. 7.3

9. 7.3

10. Uncertainty Principle Problem of defining nature of electrons in atoms solved by W. Heisenberg. It is impossible to describe the exact location of an electron. W. Heisenberg 1901-1976

11. II. Quantumtheory A. ground state – when electrons are in their lowest energy B. 4 quantum numbers b. the greatest number of electrons in an energy level is indicated by the equation - 2n2 1. principle quantum number a. energy level, n, 1,2,3,4,5

12. 2. energy sublevels and orbital a. energy states in an energy level, l b. the number of energy states = the energy level i. 1 has 1, 2 has 2 ect ii. s p d f special people deserve fudge

13. 3. orientation in space a. s - spherical b. p - dumbbell x,y, z c. d - 5 orientations d. f - 7

14. 4. spin of electrons • electrons spin - must have opposite spins • in order to be in same orbital b. orbital - space occupied by a pair of electrons

15. (s orbitals) 1s 7.6

16. p Orbitals • The three p orbitals lie 90o apart in space

17. (d orbitals) 7.6

18. f Orbital

19. n=2 n=1 n=3 principal quantum number n n = 1, 2, 3, 4, …. 7.6

20. n= 3d 3 2 1 Boundary surfaces for all orbitals of the n = 1, n = 2 and n = 3 shells There are n2 orbitals in the nth SHELL

21. The last quantum number is the spin quantum number Electrons act as though they spin about an axis through their centers. Because there are two directions in which they can spin, the spin quantum number has 2 values

22. Orbital diagram Use lines to represent the orbital's and arrows to represent electrons H 1s

23. ? ? “Fill up” electrons in lowest energy orbitals (Aufbau principle) C 6 electrons B 5 electrons Be 4 electrons Li 3 electrons H 1 electron He 2 electrons 7.7

24. The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins (Hund’s rule). C 6 electrons N 7 electrons F 9 electrons Ne 10 electrons O 8 electrons 7.7

25. 2p 2p Paramagnetic Diamagnetic unpaired electrons all electrons paired 7.8

26. number of electrons in the orbital or subshell principal quantum number n Sublevel (angular momentum) quantum number l Electron configuration is how the electrons are distributed among the various atomic orbitals in an atom. 1s1 7.8

27. ? ? “Fill up” electrons in lowest energy orbitals (Aufbau principle) C 6 electrons Li 3 electrons Be 4 electrons B 1s2 2s2 2p1 Li 1s2 2s1 Be 1s2 2s2 B 5 electrons H 1 electron He 2 electrons He 1s2 H 1s1 7.7

28. The most stable arrangement of electrons in subshells is the one with the greatest number of parallel spins (Hund’s rule). C 6 electrons N 7 electrons O 8 electrons F 9 electrons Ne 10 electrons C 1s2 2s2 2p2 N 1s2 2s2 2p3 Ne 1s2 2s2 2p6 O 1s2 2s2 2p4 F 1s2 2s2 2p5 7.7

29. Noble gas notation Use the nearest noble gas that is behindthe element and then add to it e.g write the noble gas notation for Na Ne is the nearest noble gas – its configuration is 1s2 2s2 2p6 Therefore [Ne] indicates 1s2 2s2 2p6 Na would be [Ne] 3s1

30. What is the electron configuration and noble gas notation of Mg? Mg 12 electrons 1s < 2s < 2p < 3s < 3p < 4s 1s2 2s2 2p6 3s2 2 + 2 + 6 + 2 = 12 electrons [Ne] = 1s22s22p6 Abbreviated as [Ne]3s2 7.8

31. What are the possible quantum numbers for the last (outermost) electron in Cl? Cl 17 electrons 1s < 2s < 2p < 3s < 3p < 4s 1s2 2s2 2p6 3s2 3p5 2 + 2 + 6 + 2 + 5 = 17 electrons Last electron added to 3p orbital n = 3 l=p

32. Try These! • Write the shorthand (Noble gas notation) for: Cu W Au [Ar] 4s2 3d9 [Xe] 6s2 4f14 5d4 [Xe] 6s2 4f14 5d9

33. Electron dot diagrams Valence electrons – those electrons in the outer most energy Level (those with the highest number) Mg12 Mg 1s2 2s2 2p6 3s2 Mg has 2 valence electrons

34. Fe26 1s2 2s2 2p6 3s2 3p6 4s2 3d6 Fe only has 2 valence electrons Fe

35. S16 1s2 2s2 2p6 3s2 3p4 S

36. A X Mass Number Element Symbol Z Atomic Number 2 3 1 H (D) H (T) H 1 1 1 235 238 U U 92 92 Atomic number (Z) = number of protons in nucleus Mass number (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons Isotopes are atoms of the same element (X) with different numbers of neutrons in their nuclei 2.3

37. 2.3

38. 14 11 C C 6 6 How many protons, neutrons, and electrons are in How many protons, neutrons, and electrons are in ? ? Do You Understand Isotopes? d. Canal rays - in 1886 Eugen Goldstein observed a cathode ray tube also generates a stream of positively charged particles 6 protons, 8 (14 - 6) neutrons, 6 electrons 6 protons, 5 (11 - 6) neutrons, 6 electrons 2.3

39. Odds and ends VI. Hund’s rule - electrons must be placed in each orbital before pairing them up VII. Valance electrons - those in the outer most energy level - gives elements its chemical properties VIII. orbital notation - lines IX. Electron configuration - 1s2 2s2 2p6 X. Nobel gas notation - {Ar} 4s1 XI. Electron dot notation - only use the valance electron

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