1 / 70

Chapter Three

Chapter 3. Chapter Three. Atoms and the Periodic Table. Dalton’s Atomic Theory (1808).

rosalyn-lynch
Télécharger la présentation

Chapter Three

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 3 Chapter Three Atoms and the Periodic Table

  2. Dalton’s Atomic Theory (1808) • Elements are composed of extremely small particles called atoms. All atoms of a given element are identical, having the same size,and chemical properties. The atoms of one element are different from the atoms of all other elements. • Compounds are composed of atoms of more than one element. The relative number of atoms of each element in a given compound is always the same. • Chemical reactions only involve the rearrangement of atoms. Atoms are not created or destroyed in chemical reactions. 2.1

  3. What are atoms composed of ?

  4. The Structure of Atoms • Cathode-Ray Tube (Thomson, 1856–1940): • Cathode raysconsist of tinynegativelycharged particles, now calledelectrons.

  5. The Structure of Atoms • Oil Drop Experiment (Millikan, 1868–1953): Applied a voltage to oppose the downward fall of charged drops and suspend them. • Voltage on plates place 1.602176 x 10-19 C of charge on each oil drop. • Millikan calculated the electron’s mass as 9.109382 x 10-28 grams.

  6. The Structure of Atoms • Discovery of Nucleus (Rutherford, 1871 – 1937): • Rutherford irradiatedgold foil with a beamof alpha () particlesto search for positivecharged particles.

  7. The Structure of Atoms Discovery of Nucleus (Rutherford, 1871–1937): Rutherford irradiatedgold foil with a beamof alpha () particlesto search for positivecharged particles. Atom must be mostly empty space except for a central positive mass concentration.

  8. The Structure of Atoms • Structure of the Atom:

  9. Atomic Number • The atomic number is equal to the number of protons in an atom. • On the periodic chart, the atomic number appears above the symbol of an element. 11 Na Atomic Number Symbol

  10. Atomic Numbers and Protons for Lithium and Carbon Atoms

  11. Subatomic Particles • Chemists are interested in three particles in atoms: protons, electrons, and neutrons. • Protons have a positive (+) charge; electrons have a negative (-) charge. • Like charges repel and unlike charges attract.

  12. Summary of Subatomic Particles

  13. Structure of the Atom • An atom consists of a nucleus and a cloud of electrons. • The nucleus contains all of the protons and neutrons. • The rest of the atom, which is mostly empty space, is occupied by the electrons.

  14. Learning Check State the number of protons in each. A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons

  15. Solution State the number of protons in each. A. Nitrogen 2) Atomic number 7; 7 protons B. Sulfur 2) Atomic number 16; 16 protons C. Barium 3) Atomic number 56; 56 protons

  16. Electrons in An Atom • An atom is electrically neutral; the net charge is zero. • In an atom, the number of protons is equal to the number of electrons. # protons = # electrons • Therefore, the atomic numberis also equal to the number of electrons in a neutral atom.

  17. Mass Number • The mass number gives the total number of protons and neutrons in the nucleus.Mass number = # protons + # neutrons

  18. Atomic Symbol • The atomic symbol represents a particular atom of an element. • The atomic symbol shows the mass number in the upper left cornerand the atomic number in thelower left corner. • For example, an atom of sodium with atomic number 11 and a mass number 23 has the following atomic symbol:mass number 23 Na atomic number 11

  19. Information from Atomic Symbols • When we know the atomic symbol of an atom, we can determine the number of protons (p+), neutrons, (n), and electrons (e-). 16 31 65 O P Zn 8 15 30 8 p+ 15 p+ 30 p+ 8 n 16 n 35 n 8 e- 15e- 30 e-

  20. Learning Check Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of the following. 12C 13C 14C 6 6 6 protons ______ ______ ______ neutrons ______ ______ ______ electrons ______ ______ ______

  21. Solution 12C 13C 14C 6 6 6 Protons 6 6 6 Neutrons 6 7 8 Electrons 6 6 6

  22. Learning Check Write the atomic symbols for atoms with the following subatomic particles: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 47 e- ___________

  23. Solution Write the atomic symbols for atoms with the following subatomic particles: 16O A. 8 p+, 8 n, 8 e- 8 B. 17p+, 20n, 17e- 37Cl 17 C. 47p+, 60 n, 47 e- 107Ag 47

  24. Learning Check An atom of zinc has a mass number of 65. A. How many protons are in this zinc atom? 1) 30 2) 35 3) 65 B. How many neutrons are in the zinc atom? 1) 30 2) 35 3) 65 C. What is the mass number of a zinc atom that has 37 neutrons? 1) 37 2) 65 3) 67

  25. Solution An atom of zinc has a mass number of 65. A. How many protons are in this zinc atom? 1) 30 B. How many neutrons are in the zinc atom? 2) 35 C. What is the mass number of a zinc atom that has 37 neutrons? 3) 67

  26. Learning Check An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is 1) 14 2) 16 3) 34 C. The element is 1) Si 2) Ca 3) Se

  27. Solution An atom has 14 protons and 20 neutrons. A. It has atomic number 1) 14 B. It has a mass number of 3) 34 C. The element is 1) Si

  28. 2.5 Isotopes and Atomic Mass 24Mg 25Mg 26Mg 12 12 12

  29. Isotopes • Isotopes are atoms of the same element that have different mass numbers. • Isotopes have the same number of protons, but different numbers of neutrons. All elements have two or more isotopes.

  30. Isotopes of Magnesium In naturally occurring atoms of magnesium, there are three isotopes. • 24Mg makes up 78.9% of magnesium atoms. • 25Mg makes up 10.0% and 26Mg makes up 11.1%. 24Mg 25Mg 26Mg 12 12 12

  31. Learning Check Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium __________ B. aluminum __________ C. lead __________ D. barium __________ E. iron __________

  32. Solution Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium 40.1 amu B. aluminum 27.0 amu C. lead 207.2 amu D. barium 137.3 amu E. iron 55.8 amu

  33. 3. 6 Electronic Structure of Atoms • Quantum mechanical model of atomic structure: • Electrons are not perfectly free to move about in an atom. • Each electron is restricted to moving about only in a certain region of space within the atom, depending on the amount of energy the electron has.

  34. Probability distribution (2) for an electron in a 1s orbital.

  35. A boundary surface encloses the regionwhere the probability of finding an electronis high—on the order of 90-95% 1s 2s Boundary surfaces of a 1s orbitaland a 2s orbital.

  36. Different orbitals have different shapes. Orbitals in s subshells are spherical (a), while orbitals in p subshells are roughly dumbbell shaped (b).

  37. s and p Orbitals • In an atom, all the orbitals are centered around the nucleus. For example, the illustration of the combination of s and p orbitals is

  38. Subshells and Orbitals Each subshell has a specific number of orbitals. • Each s subshell contains one s orbital. • Each p subshell contains three p orbitals. • Each d subshell contains five d orbitals. • Each f subshell contains seven f orbitals.

  39. d-Orbitals

  40. f-Orbitals

  41. The first shell has only an s subshell • The second shell has an s and a p subshell • The third shell has an s, a p, and a d subshell. • The fourth shell has an s, a p, a d, and an f subshell.

  42. The number of subshells in a given shell is equal to the shell number. For example, shell number 3 has 3 subshells. • Within each subshell, electrons are further grouped into orbitals, regions of space within an atom where the specific electrons are more likely to be found. • There are different number of orbitals within the diff erent kinds of subshells.

  43. Energy of Electrons • Different electrons have different amounts of energy and thus occupy different regions within the atom. • The energies of electrons are quantized, or restricted to having only certain values. • The electrons in an atom are grouped around the nucleus into shells. • Within the shells, electrons are further grouped into sub shells of four different types, identified as s, p, d, and f in order of increasing energy.

  44. Electrons fill orbitals in ascending order, from the lowest-energy orbitals upward. Generally, this means that lower-numbered shells fill before higher-numbered shells. However, some overlap in energy levels occurs starting in the third energy level. Fig 3.5 order of orbital energy levels

  45. 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p

  46. 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p Some Electron Configurations First Period H 1s1 He 1s2 Second Period Li 1s2 2s1 C 1s2 2s2 2p2 Third Period Na 1s2 2s2 2p6 3s1 Al 1s2 2s2 2p6 3s2 3p1 S 1s2 2s2 2p6 3s2 3p4

  47. Electronic configuration of a few elements are shown below:

  48. Electron Configurations for Elements

More Related