What makes an atom of one element different from an atom of another element?
Atoms of different elements contain different numbers of protons.
For example, oxygen atom contain 8 protons; nitrogen atom contain 7 protons.
Different elements have different atomic numbers.
ATOMIC NUMBER (Z)
Also
known
as proton number
Number
of protons in the nucleus of each atom of an element.
In
neutral atom, number of protons =
number of electrons
In ions, number of electrons = number of protons - (Charge)
In ions, number of electrons = number of protons - (Charge)
Also known as nucleon number
The
total number of protons and neutrons present in the nucleus of an atom of an
element.
Number
of Neutrons = Mass Number (A) – Atomic Number (Z)
ISOTOPES NOTATION
Most elements occur in nature as mixtures of isotopes.
Atoms with identical atomic numbers but different mass numbers are called isotopes.
Isotopes are represented by symbols such as this: 
. The symbol represents "carbon twelve", carbon-12.
. The symbol represents "carbon twelve", carbon-12. 
The atomic number is shown by the subscript and the mass number is shown by the superscript.
ATOMS
– Differ by number of protons
IONS
– Differ by number of electrons
ISOTOPES
– Differ by number of neutrons
Example 1: What is the isotopic notation for the isotope carbon-14?
From the periodic table, we see that the atomic number (number of protons) for the element carbon is 6 14
Answers:
The chemical symbol for carbon isC
Answers:
The chemical symbol for carbon is
We can determine the number of neutrons as 14−6=8
Example 2. Given the isotopic notation
a) Name of the isotope
b) Mass number
c) Atomic number
d) Number of protons
e) Number of neutrons.
b) Mass number
c) Atomic number
d) Number of protons
e) Number of neutrons.
Answers:
a) titanium-48
b)48
c)22
d)22
e)48−22=26
b)
c)
d)
e)
Example 3. How many protons, neutrons, and electrons are in an atom of 197Au?
Answers:
The superscript 197 is the mass number, the sum of the numbers of protons and neutrons. According to the list of elements given on the front inside cover of this text, gold has an atomic number of 79. Consequently, an atom of 197Au has 79 protons, 79 electrons, and 197 - 79 = 118 neutrons.
Example 4. How many protons, neutrons, and electrons are in a Si-28, Br-79, P-32 and I-125 ?
Answers:
Example 5. How many protons, neutrons, and electrons are in a 138Ba atom?
Answers:
56 protons, 56 electrons, and 82 neutrons
Example 6.
Determine the numbers of protons, neutrons, and electrons in each silicone isotope.
(Refer to the periodic table for the atomic number)Answers:
Example 7.
Give
the number of protons and electrons in each of
the following common ions:
K+, Mg2+, Fe3+, Br–, Mn2+, C4–, Cu2+.
Answers:
Numerical list of Atomic Numbers of Elements
| Name of Element | Symbol of Element | Number of Protons / Electrons | Mass Number | Atomic Number | Number of Neutrons |
| Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Cesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Ununbium Ununtrium Ununquadium Ununpentium Ununhexium Ununseptium Ununoctium | H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Uub Uut Uuq Uup Uuh Uus Uuo | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 19 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 | 1 4 7 9 11 12 14 16 19 20 23 24 27 28 31 32 35 40 30 40 45 48 51 52 55 56 58 58 64 65 70 73 75 79 80 84 85 88 89 91 93 96 98 101 103 106 108 112 115 119 122 128 127 131 133 137 139 140 141 144 145 150 152 157 159 163 165 167 169 173 175 178 181 184 186 190 192 195 197 201 204 207 209 209 210 222 223 226 227 232 231 238 237 244 243 247 247 251 252 257 258 259 262 261 268 263 264 269 268 272 273 277 286 289 288 292 292 293 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 | 0 2 4 5 6 6 7 8 10 10 12 12 14 14 16 16 18 22 21 20 24 26 28 28 30 30 31 30 35 35 39 41 42 45 45 48 48 50 50 51 52 54 55 57 58 60 61 64 66 69 71 76 74 77 78 81 82 82 82 84 84 88 89 93 94 97 98 99 100 103 104 106 108 110 111 114 115 117 118 121 123 125 126 125 125 136 136 138 138 142 140 146 144 150 148 151 150 153 153 157 157 157 159 157 N/A 157 157 161 159 162 162 165 173 175 173 176 175 175 |
| Name of Element (Alphabeticallist) | Symbol of Element | Number of Protons Electrons | Mass Number | Atomic Number | Number of Neutrons |
Numerical list of Atomic Numbers of Elements
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