Classification of Elements

Introduction to Elements

What are elements?

Elements are pure substances made of only one type of atom. For example, gold (Au), oxygen (O₂), and sodium (Na) are elements.

Why classify them?

Scientists noticed that some elements behave similarly (e.g., sodium and potassium both react violently with water). By grouping them, we can:

Early Attempts: Mendeleev’s Periodic Table (1869)

Basis: Atomic weight (average mass of an element’s atoms).

Mendeleev’s Periodic Law:

"The properties of elements are periodic functions of their atomic weights."

Key Features/Properties:

Limitations:

Mendeleev’s Periodic Table

Mendeleev's Periodic Table

Modern Periodic Table(Henry Moseley, 1913)

Basis: Atomic number (number of protons).

Modern Periodic Law:

"The properties of elements are periodic functions of their atomic numbers."

Properties:

Limitations:

Modern Periodic Table

1 IA
18 VIIIA
1 1.008 H Hydrogen
2 IIA
13 IIIA
14 IVA
15 VA
16 VIA
17 VIIA
2 4.0026 He Helium
3 6.94 Li Lithium
4 9.0122 Be Beryllium
5 10.81 B Boron
6 12.011 C Carbon
7 14.007 N Nitrogen
8 15.999 O Oxygen
9 18.998 F Fluorine
10 20.180 Ne Neon
11 22.990 Na Sodium
12 24.305 Mg Magnesium
3 IIIB
4 IVB
5 VB
6 VIB
7 VIIB
8 VIIIB
9 VIIIA
10 VIIIA
11 IB
12 IIB
13 26.982 Al Aluminum
14 28.085 Si Silicon
15 30.974 P Phosphorus
16 32.06 S Sulfur
17 35.45 Cl Chlorine
18 39.948 Ar Argon
19 39.098 K Potassium
20 40.078 Ca Calcium
21 44.956 Sc Scandium
22 47.867 Ti Titanium
23 50.942 V Vanadium
24 51.996 Cr Chromium
25 54.938 Mn Manganese
26 55.845 Fe Iron
27 58.933 Co Cobalt
28 58.693 Ni Nickel
29 63.546 Cu Copper
30 65.38 Zn Zinc
31 69.723 Ga Gallium
32 72.630 Ge Germanium
33 74.922 As Arsenic
34 78.971 Se Selenium
35 79.904 Br Bromine
36 83.798 Kr Krypton
37 85.468 Rb Rubidium
38 87.62 Sr Strontium
39 88.906 Y Yttrium
40 91.224 Zr Zirconium
41 92.906 Nb Niobium
42 95.95 Mo Molybdenum
43 (98) Tc Technetium
44 101.07 Ru Ruthenium
45 102.91 Rh Rhodium
46 106.42 Pd Palladium
47 107.87 Ag Silver
48 112.41 Cd Cadmium
49 114.82 In Indium
50 118.71 Sn Tin
51 121.76 Sb Antimony
52 127.60 Te Tellurium
53 126.90 I Iodine
54 131.29 Xe Xenon
55 132.91 Cs Cesium
56 137.33 Ba Barium
Lanthanides 57-71
72 178.49 Hf Hafnium
73 180.95 Ta Tantalum
74 183.84 W Tungsten
75 186.21 Re Rhenium
76 190.23 Os Osmium
77 192.22 Ir Iridium
78 195.08 Pt Platinum
79 196.97 Au Gold
80 200.59 Hg Mercury
81 204.38 Tl Thallium
82 207.2 Pb Lead
83 208.98 Bi Bismuth
84 (209) Po Polonium
85 (210) At Astatine
86 (222) Rn Radon
87 (223) Fr Francium
88 (226) Ra Radium
Actinides 89-103
104 (267) Rf Rutherfordium
105 (268) Db Dubnium
106 (271) Sg Seaborgium
107 (272) Bh Bohrium
108 (277) Hs Hassium
109 (278) Mt Meitnerium
110 (281) Ds Darmstadtium
111 (282) Rg Roentgenium
112 (285) Cn Copernicium
113 (286) Nh Nihonium
114 (289) Fl Flerovium
115 (290) Mc Moscovium
116 (293) Lv Livermorium
117 (294) Ts Tennessine
118 (294) Og Oganesson
57 138.91 La Lanthanum
58 140.12 Ce Cerium
59 140.91 Pr Praseodymium
60 144.24 Nd Neodymium
61 (145) Pm Promethium
62 150.36 Sm Samarium
63 151.96 Eu Europium
64 157.25 Gd Gadolinium
65 158.93 Tb Terbium
66 162.50 Dy Dysprosium
67 164.93 Ho Holmium
68 167.26 Er Erbium
69 168.93 Tm Thulium
70 173.05 Yb Ytterbium
71 174.97 Lu Lutetium
89 227 Ac Actinium
90 232.04 Th Thorium
91 231.04 Pa Protactinium
92 238.03 U Uranium
93 (237) Np Neptunium
94 (244) Pu Plutonium
95 (243) Am Americium
96 (247) Cm Curium
97 (247) Bk Berkelium
98 (251) Cf Californium
99 (252) Es Einsteinium
100 (257) Fm Fermium
101 (258) Md Mendelevium
102 (259) No Nobelium
103 (262) Lr Lawrencium

Sub-category

Alkali Metals
Alkali Earth Metals
Transition Metals
Post-Transition Metals
Metalloids
Reactive Non-Metals
Noble Gas
Lanthanides
Actinides
Unknown Properties
1 1.008 H Hydrogen
Atomic Number
Atomic Weight
Symbol
Name

State Of Matter [Text-Color]

Solid
Liquid
Gas

Electronic Configuration

"The path in which electrons revolve around the nucleus of an atom is called orbit or shell."

Shells and Subshells

A shell can be divided into one or more subshells, which contain orbitals where electrons are found.

Shell Sub-shells Total Electrons
K 1s 2
L 2s,2p 8
M 3s, 3p, 3d 18
N 4s, 4p, 4d, 4f 32

Sub-shells can accommodate a maximum number of electrons.

Aufbau's Principle

Aufbau's principle dictates that electrons fill subshells in order of increasing energy:1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p

Classification: Metals, Non-metals, and Metalloids

Elements are classified into three groups based on metallic character.

Metal

Non-Metals

Metalloids

Trends in the Periodic Table

Valency

Atomic Size

Electropositivity and Electronegativity

Chemical Reactivity