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Chapter 2 Atoms

Chemistry B11. Chapter 2 Atoms. Matter Anything that occupies space and has mass. Physically Separable into. Pure substances Fixed composition, cannot be more purified. Mixtures A combination of two or more pure substances. Element Cannot be subdivided by chemical or

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Chapter 2 Atoms

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  1. Chemistry B11 Chapter 2 Atoms

  2. Matter Anything that occupies space and has mass Physically Separable into Pure substances Fixed composition, cannot be more purified Mixtures A combination of two or more pure substances Element Cannot be subdivided by chemical or physical means Compounds Elements united In fixed ratios Heterogeneous matter Nonuniform composition Homogeneous matter Uniform Composition throughout Combine Chemically To form

  3. Element: is a substance consists of identical atoms. Cannot be divided by chemical & physical methods. Carbon, Hydrogen, Oxygen 116 elements – 88 in nature Compound: is a pure substance made up of two or more elements in a fixed ratio by mass. H2O (Water): 2 Hydrogen & 1 Oxygen CO2: 1 Carbon & 2 Oxygen 20 million compounds

  4. 2 H or = 2 : 1 1 O 1 C or = 1 : 1 1 O Compounds Formula Identifies each element Ratios H2O CO

  5. H2O O H H Molecular formula Space-filling model Structural formula Ball-and-stick model H H C H H Molecular models CH4

  6. Mixtures Mixture:is a combination of two or more pure substances. Homogeneous: uniform & throughout Air, Salt in water Heterogeneous: nonuniform Soup, Milk, Blood

  7. Dalton’s Atomic theory • All matter is made up of very tiny, indivisible particles (atoms). • All atoms of a given element have the same chemical properties. • Compounds are formed by the chemical combination of two or • more different kinds of atoms. • 4. A molecule is a bound combination of two or more atoms. Law of conservation of mass: C + O  CO

  8. Element: Monatomic Diatomic Polyatomic Ar He N2 O2 S8 Atom

  9. Atom Nucleus: positive charge Atoms are neutral. Atomic mass unit (amu) = 1.6605×10-24 g mass of proton = 1 amu mass of neutron = 1 amu mass of electron = 5.48×10-4 amu

  10. Mass number 12 C Atomic number 6 Atom Mass number (A): Protons + Neutrons Atomic number (Z): Protons

  11. 12 13 14 C C C 6 6 6 Isotopes Isotopes: atoms with the same number of protons and electrons but different numbers of neutrons. different mass numbers 6 P + 6 N 6 P + 8 N 6 P + 7 N Almost the same properties

  12. Atomic number 17 Cl Atomic weight 35.45 Atomic Weight Atomic weight: of an element is average of the masses (in amu) of its isotopes found on the Earth. Cl 37 35 Cl Cl 36.97 amu 34.97 amu 17 17 (75.77/100 × 34.97 amu) + (24.23/100 × 36.97 amu) = 35.45 amu

  13. Main-group elements: 1A to 8A Transition elements: 1B to 8B (3 – 12) Inner transition elements: between B3 & B4 (58 to 71 and 90 to 103) Column: same properties (main group) Row or Period

  14. Group 2A: Alkaline metals or Earth metals Be-Mg-Ca-Sr-Ba-Ra reactive, solid metal Group 1A: Alkali metals Li-Na-K-Rb-Cs-Fr too reactive, unstable, solid metal 2Na + 2H2O 2NaOH + H2 2Na + Cl2 2NaCl

  15. Group 7A: Halogens F-Cl-Br-I-At reactive, colored, gas, nonmetal Group 8A: Noble gases He-Ne-Ar-Kr-Xe-Rn non reactive, stable, gas, nonmetal

  16. t o Classification of the elements metals nonmetals metalloids metals: solid (except mercury), shiny, conductors of electricity, ductile, malleable nonmetals: solid, liquid or gas, do not conduct electricity (except graphite) metalloids: between metals and nonmetals

  17. Metallic properties More metallic More metallic

  18. n=1 n=5 n=2 n=3 n=4 Shell Maximum number of electrons Lower energy 1 2 2 8 3 18 4 32 Higher energy Bohr model E1 E2 E3 E4 E5 Principal energy levels or Shells E1 = ground state: lowest energy level

  19. magnetic field paired spins Subshell: s p d f Orbital: is a region of space and it can hold 2 electrons (max). s px py pz

  20. Subshell: s p d f p s d f 2 2+2+2+2+2=10 2+2+2+2+2+2+2=14 2+2+2=6

  21. 3d 3p 3 3s Energy Order of filling 2p 2 2s 1s 1 Principal energy level Orbitals

  22. 1s1 H (1) 1s 1s2 He (2) 1s 1s2 2s1 Li (3) 2s 1s 1s2 2s2 2p2 C (6) 2px 2py 2pz 2s 1s Electrons configuration: description of the orbitals that its electrons occupy. Orbital box diagrams Electron configuration

  23. 1s2 2s2 2p5 F (9) [He] 2s2 2p5 2px 2py 2pz 2s 1s Si (14) 2s 2px 2py 1s 3px 3py 2pz 3s 3pz 1s2 2s2 2p6 3s2 3p2 [Ne] 3s2 3p2 Noble gas notation 1s2 2s1 Li (3) 2s 1s [He] 2s1

  24. Noble gases Filled valence shells Valence shell: outer shell Valence electrons: outer-shell electrons Cl (17) 1s2 2s2 2p6 3s2 3p5 7 valence electrons 1s2 2s2 2p6 3s2 3p6 Ar (18) 8 valence electrons C (6) 1s22s2 2p2 4 valence electrons 8 valence electrons 1s22s2 2p6 Ne (10)

  25. For Main-group elements: Elements in the same column (group) have the same number of electrons in their valance shells. The same chemical and physical properties.

  26. C H Cl 1A 2A 3A 4A 5A 6A 7A 8A Lewis dot structure Li He

  27. Main groups elements s, p Transition elements s, p, d Inner transition elements s, p, d, f

  28. Atomic Size Size of an atom: is the size of its outermost occupied orbital. d

  29. Ionization Energy Li + energy → Li+ + e- ion Ionization energy: the energy required to remove the most loosely held electron from an atom in the gaseous state. Ionization energy Ionization energy

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