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What is an Atomic Number?

Atom

"The Atom"

What is an Atomic Number?
Each Chemical element on the Periodic table is given a unique Atomic Number - a Periodic Table Number. Atoms are made up of three kinds of smaller particles, called protons, neutrons and electrons. The atomic number is the number of protons in the atom. Atoms must have equal numbers of protons and electrons. The chemical elements of the periodic table are listed in order of atomic number

What is an Atomic Number? What are Protons and Electrons?
Protons and electrons have different properties. Electrons are tiny, very light particles that have a negative electrical charge. Protons are much larger and heavier than electrons and have a positive charge.

What is an Atomic Number?
In 1913 the English scientist, Henry Moseley, determined the atomic number of each of the elements and modified the 'Periodic Law' accordingly. The atomic number of an element is the same as the number of electrons or protons in that particular atom. Across the Periodic table the elements are placed in the order of their atomic numbers starting with the lowest number of 1 which is the atomic number for hydrogen.

What is an Atomic Number? The Periodic Law
The Periodic Law states that the Physical and Chemical Properties of the elements recur periodically in a systematic and predictable way when the elements are arranged in order of increasing atomic number. The Periodic Table is therefore arranged in order of increasing atomic numbers according to the Periodic Law. The Periodic Law can be explained further by comparing the chemical and physical properties of elements.

What is an Atomic Number? Periodic Trends
When elements in the Periodic Table are arranged according to atomic number, elements show repeating, or periodic trends in their chemical and physical properties. The Periodic Table can therefore be used by chemists to observe chemical and physical properties, characteristics, patterns and relationships between over 100 elements in just one chart. So the Atomic Number of an element is very important. The higher the atomic number, the greater the number of protons in the nucleus. This means that more neutrons are required to "bind" the nucleus of the atom together.

What is an Atomic Number? Every number is unique...
Every element has a unique Element Symbol and a unique Atomic Number. The same Atomic Number for each element is used all over the world and instantly recognised by scientists and chemists. It is imperative for chemistry students to be able to recognise the names of elements from their Atomic number.

What is an Atomic Number? Atomic Number Chart
The following chart, or list, details the names of all of the Periodic Table elements and their corresponding Atomic Number.

List of Elements and their Atomic Numbers

Actinium: Ac :  89
Aluminium: Al :  13
Americium: Am :  95
Antimony: Sb :  51
Argon: Ar :  18
Arsenic: As :  33
Astatine: At  :  85
Barium: Ba  :  56
Berkelium: Bk :  97
Beryllium: Be :  4
Bismuth: Bi  :  83
Bohrium: Bh  :  107
Boron: B  :  5
Bromine: Br :  35
Cadmium: Cd  :  48
Cesium: Cs :  55
Calcium: Ca  :  20
Californium: Cf  :  98 
Carbon: C  :  6
Cerium: Ce  :  58
Chlorine: Cl  :  17
Chromium: Cr  :  24
Cobalt: Co  :  27
Copper: Cu  :  29
Curium: Cm   :  96
Darmstadtium: Ds  :  110
Dubnium: Db  :  105
Dysprosium: Dy :  66
Einsteinium: Es :  99
Erbium: Er :  68
Europium: Eu  :  63
Fermium: Fm  :  100
Fluorine: F  :  9
Francium: Fr  :  87
Gadolinium: Gd  :  64
Gallium: Ga  :  31
Germanium: Ge  :  32
Gold: Au :  79
Hafnium: Hf :  72
Hassium: Hs  :  108
Helium: He  :  2
Holmium: Ho  : 67
Hydrogen: H  :  1
Indium: In  :  49
Iodine: I   : 53
Iridium: Ir  :  77 
Iron: Fe  :  26
Krypton: Kr  :  36 
Lanthanum: La  :  57
Lawrencium: Lr  :  103
Lead: Pb  :  82
Lithium: Li  :  3
Lutetium: Lu   :  71
Magnesium: Mg  :  12
Manganese: Mn :  25
Meitnerium: Mt  :  109
Mendelevium: Md  :  101
Mercury: Hg :  80
Molybdenum: Mo  :  42
Neodymium: Nd  :  60
Neon: Ne  :  10
Neptunium: Np  :  93
Nickel: Ni :  28
Niobium: Nb :  41
Nitrogen: N :  7
Nobelium: No  :  102
Osmium: Os :  76
Oxygen: O   :  8
Palladium: Pd  :   46
Phosphorus: P  :  15
Platinum: Pt  :  78
Plutonium: Pu  :  94
Polonium: Po  :  84
Potassium: K   :  19 
Praseodymium: Pr :  59
Promethium: Pm :  61
Protactinium: Pa   :  91
Radium: Ra   :  88
Radon: Rn :  86
Rhenium: Re  :  75
Rhodium: Rh  :  45
Roentgenium: Rg  :  111
Rubidium: Rb   :  37
Ruthenium: Ru  44
Rutherfordium: Rf  :  104
Samarium: Sm   :  62
Scandium: Sc  :  21
Seaborgium: Sg :  106 
Selenium: Se :  34
Silicon: Si   :  14
Silver: Ag  :  47
Sodium: Na   :  11
Strontium: Sr  :  38
Sulfur: S  :  16
Tantalum: Ta  :  73
Technetium: Tc :  43
Tellurium: Te  :  52
Terbium: Tb  : 65
Thallium: Tl  :  81
Thorium: Th  :  90
Thulium: Tm  :  69
Tin: Sn  :  50
Titanium: Ti  :  22
Tungsten: W  :  74
Ununbium: Uub  :  112
Ununhexium: Uuh  :  116
Ununoctium: Uuo :  118
Ununpentium: Uup  :  115
Ununquadium: Uuq   :  114
Ununseptium: Uus :  117
Ununtrium: Uut  :  113
Uranium: U  :  92
Vanadium: V  :  23
Xenon: Xe   :  54
Ytterbium: Yb  :  70
Yttrium: Y  :  39
Zinc: Zn  :  30 
Zirconium: Zr  :  40
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