Alternative transcript:

the periodic table mass number (number of protons + number of neutrons) 27 AI 13 atomic number (number of protons) = same as number of electrons Protons: (atomic no.) -13 Electrons: (same as no. of protons/atomic no.) - 13 Neutrons: (mass no. - atomic no.) - 27-13 = 14 ● ● Using the periodic table Atomic number (proton number): is the number of protons in an atom The elements are arranged in the Periodic Table in ascending order of atomic number Mass number: is the total number of protons and neutrons in an atom Relative atomic mass (Ar): is the average mass of an atom of an element compared to an atom od carbon-12 Atom boron potassium chromium mercury argon ? What are the missing numbers? Protons Neutrons Electrons 5 6 ? 24 ? ▼ ? ? 28 121 ? ? ? 19 24 80 Atomic Mass number number 5 ? ? ? 19 18 39 ? 201 40 solve ● ● ● Isotopes Isotopes are different atoms of an element with the same number of protons and electrons but different numbers of neutrons For example, two isotopes of carbon: mass number is different 12+ C 6 atomic number is the same 13 C 6 The existence of isotopes results in relative atomic masses not being whole numbers Calculating relative atomic mass • If the relative abundances are A% and B%, and the mass numbers are X and Y: ● ● ● ● Step 1: Calculate (A x X) + (B x Y) Step 2: Divide the answer from Step 1 by 100 For example, chlorine has two main isotopes: 75% of the atoms of chlorine are Cl atoms with a mass number of 35 25% of the atoms of chlorine are Cl atoms with a mass number of 37 Step 1: (75 x 35) + (25 x 37) = 2625 + 925 = 3550 Step 2: 3550 ÷ 100 = 35.5 ● How are electrons arranged? Electrons exist in electron shells (also called energy levels) • The arrangement of electrons in these shells is called the electron configuration ● Each shell has a maximum number of electrons that it can hold • Electrons fill the shells nearest the nucleus first How are electrons arranged? 1st shell holds a maximum of 2 electrons 2nd shell holds a maximum of 8 electrons 3rd shell holds a maximum of 8 electrons The electron configuration is written as 2, 8, 8 ● - - ● Electron configuration Electronic configurations can be worked out using atomic numbers For example, the atomic number of sodium is 11. This means that there are 11 protons and 11 electrons. So to fill the shells: 2 electrons fit in the first shell, leaving 9 to place 8 electrons fit in the second shell, leaving 1 to place 1 electron fits into the third shell, leaving none to place The electron configuration for sodium is: 2, 8, 1 X ХХ Na ХХ X XX Group 1 Period 1 2 3 5 6 7 lanthanides actinides 23 Na 11 39 K 19 85 Rb 37 133 Cs 2 Be 24 Mg 12 relative atomic mass- atomic number- 40 45 Cla Sc 20 21 88 Sr Y 89 38 39 137 139 Ba La 55 56 57 @FNANG SINO 48 Ti 22 91 Zr 93 Nb 41 181 Hf Ta 178 72 73 40 51 V 23 58 (223) (226) (227) (261) (262) Fr Ra Ac Rf Db 104 105 87 88 89 V V 140 141 Ce Pr 59 232 231 Th Pa 90 91 52 55 56 59 59 Cr Mn Fe Co Ni 24 25 26 27 28 96 Mo Tc 42 43 184 186 W Re 74 75 (266) Sg 106 144 Nd 60 (98) 101 238 U 92 (264) Bh 107 103 106 Pd 45 46 Ru Rh 44 190 192 195 Ir Pt Os 76 77 78 145 Pm 61 (277) Hs Mt 108 109 150 Sm 62 237 244 Np Pu 93 94 (268) (271) 152 Eu 63 108 112 Ag Cd 47 48 197 201 Au Hg 79 80 (272) Ds Rg 110 111 3 4 5 6 7 0 4 He 2 243 247 Am Cm 95 96 97 247 Bk =B57A130 11 63.5 Cu 29 30 31 27 Al 157 159 162 165 Gd Tb Dy | Ho 64 65 66 67 12 14 C N 7 6 28 65 73 75 Zn Ga Ge As 32 33 Si 14 31 P 15 16 O 8 19 F 9 251 252 Cf Es 98 99 100 32 35.5 40 S CI Ar 16 17 18 79 80 Se Br 34 35 115 In 49 204 207 209 (209) (210) TI Pb 81 82 83 131 119 122 128 127 Sn Sb Te I Xe 50 51 52 53 54 (222) Bi Po At Rn 84 85 86 167 169 173 175 Er Tm Yb 68 20 Ne 10 69 70 71 257 258 259 262 Fm Md No Lr 101 102 103 84 Kr 36 1 H Li Na K 2 Be Mg 3 B Al C Si 5 N P S 7 F CI Group number: shows the number of electrons in the outer shell Period number: shows the number of electron shells He Ne Ar