III. Atomic Structure A. Components of atoms + - a) electron, e - (negatively charged), -1.6 x C mass = 1/1838 that of a H atom Chapter 3 1

b) proton, p + (positively charged) mass mass of H atom 2

Charge and Mass Characteristics of Electrons, Protons, and Neutrons. c) Neutron, n (no charged) mass mass of H atom unit charge electron, e - (negatively charged), -1.6 x C 3

atomic number, Z = number of protons in an atom of a given element mass number, A = # of protons + # of neutrons = (# of nucleons) d) Symbols of elements X A Z Examples 4

B. Isotopes Not all atoms of the same element have the same mass Example: There are 3 kinds of Hydrogen atoms H D T hydrogen-1 hydrogen-2 hydrogen-3 (protium) (deuterium) (Tritium) mass ratio Symbol H H H 1 e -, 1 p + 1 e -, 1 p +,1 n Isotopes: Atoms with the same # of p + s and e - s but different # of n's. They have the same chemical properties except that they are different in mass 5

Examples Isotopes are atoms of the same element with different number of neutrons. C All atoms of an element have the same atomic # 6

C. Atomic mass (weight) – mass of an atom Atomic mass unit (amu) Mass of a H atom = x g H amu He amu Li 7373 (3p + s,4 n s) C (6 p + s, 6 n s) amu = x g In the periodic table, not all atomic masses (atomic weights) are close to a whole number because of the existence of isotopes. 7

Figure 3.3 The periodic table of the elements Group period 8

Example: Cl 35 Cl 37 Cl 75% 25% 9

Alkali metals Alkaline earth metals Halogens Noble gases 10

(Main group elements) 11

Selected Physical Properties of Metals and Nonmetals. Nonmetals Except for hydrogen (H), they lie on the right side of the Periodic Table. Except for graphite, do not conduct electricity. In chemical reactions, they tend to accept electrons. Metals are solids at room temperature (except for Hg, which is a liquid), shiny, conduct electricity, and are ductile and malleable. form alloys (solutions of one metal dissolved in another); brass, for example, is an alloy of copper and zinc In chemical reactions, they tend to give up electrons. 12

Metalloids They have some of the properties of metals and some of nonmetals; for example, they are shiny like metals but do not conduct electricity. Six elements are classified as metalloids: boron, silicon, germanium, arsenic, antimony, and tellurium. One of the metalloids, silicon, is a semiconductor; it does not conduct electricity under certain applied voltages, but becomes a conductor at higher applied voltages. 13

Tc 14

D. The inner structure of the atom Rutherford’s experiment Observations 1.Most of them (  particles) went right through 2. A few deflected 3. Some bounced back from the gold foil He 2+ 15

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IV. Electron configuration of atoms A. Experimental facts (Flame test) A pure substance absorbs only certain energies and emit certain energies. From quantum mechanical calculations, electrons can be in discrete energy levels only Bohr 18

IV. Electron configuration of atoms A. Experimental facts A pure substance absorbs only certain energies and emit certain energies. From quantum mechanical calculations, electrons can be in discrete energy levels only Bohr 19

B. Energy levels

Energy levels a)Shells and subshells 21

b) Orbitals Further studies indicate that electrons do not travel in circles 22

Standing wave 23

p orbitals z 24

d orbitals 25

Figure

c) Electron Spin An electron in an orbital can either spin up or spin down spin up Spin down electron pair 27

Electron Configuration and Orbital Diagrams 1s 2s 2p 3s 3p H 1s 1 Orbital (box) diagram Electron configuration He 1s 2 Pauli exclusive principle 28

Electron Configuration and Orbital Diagrams 1s 2s 2p 3s 3p Orbital diagram Electron configuration 29

1s 2s 2p 3s 3p Orbital diagram Electron configuration 30

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1s 2s 2p 3s 3p Orbital (box) diagramElectron configuration 4s 3d 4p 32

1s 2s 2p 3s 3p 4s 3d 4p 33

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1s 2s 2p 3s 3p Orbital diagramElectron configuration 4s 3d 4p 35

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3d 4d 5d 6d 4s 5s 6s 7s 2s 3s 2p 3p 5p 6p 4f 5f 4p 37

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3d 4d 5d 6d 4s 5s 6s 7s 2s 3s 2p 3p 5p 6p 4f 5f 4p Os 1s 2 2s 2 2p 6 …………… 5d 6 39