First 20 Elements of the Periodic Table with Atomic Number

The modern day periodic table contains 118 known elements. The first 20 elements starting from hydrogen to calcium are very important for understanding the basics of chemistry.

In this article we will take a brief look at the first 20 chemical elements of the periodic table along with their symbol and atomic number. Apart from this guide we also provided their electron configuration.

Atomic Number of First 20 Elements

The atomic number of elements provides the details of the number of protons inside the nuclei of the atom and also the number of electrons that surround these nuclei. For example: the atomic number of calcium 20. Which means the nucleus contains 20 protons and is surrounded by 20 electrons. The atomic number of an atom is calculated by the number of electrons it contains and also this number is used to find the electronic configuration of the element.

Atomic Number	Element	Symbol
1	Hydrogen	H
2	Helium	He
3	Lithium	Li
4	Beryllium	Be
5	Boron	B
6	Carbon	C
7	Nitrogen	N
8	Oxygen	O
9	Fluorine	F
10	Neon	Ne
11	Sodium	Na
12	Magnesium	Mg
13	Aluminium	Al
14	Silicon	Si
15	Phosphorus	P
16	Sulphur	S
17	Chlorine	Cl
18	Argon	Ar
19	Potassium	K
20	Calcium	Ca

Electronic Configuration of 20 Elements

Electronic configuration is the arrangement of electrons in the different shells around the nucleus of the atom. The first shell is called K, the second is L, third M and fourth N. For example sodium has an atomic number of 11. Its electronic configuration is 2, 8, 1. This means K shell has 2 electrons, L shell has 8 electrons and M shell has 1 electron. Here is the electronic configuration of the first 20 elements.

Atomic Number	Element	Configuration
1	Hydrogen	1s¹
2	Helium	1s²
3	Lithium	1s² 2s¹
4	Beryllium	1s² 2s²
5	Boron	1s² 2s² 2p¹
6	Carbon	1s² 2s² 2p²
7	Nitrogen	1s² 2s² 2p³
8	Oxygen	1s² 2s² 2p⁴
9	Fluorine	1s² 2s² 2p⁵
10	Neon	1s² 2s² 2p⁶
11	Sodium	1s² 2s² 2p⁶ 3s¹
12	Magnesium	1s² 2s² 2p⁶ 3s²
13	Aluminium	1s² 2s² 2p⁶ 3s² 3p¹
14	Silicon	1s² 2s² 2p⁶ 3s² 3p²
15	Phosphorus	1s² 2s² 2p⁶ 3s² 3p³
16	Sulphur	1s² 2s² 2p⁶ 3s² 3p⁴
17	Chlorine	1s² 2s² 2p⁶ 3s² 3p⁵
18	Argon	1s² 2s² 2p⁶ 3s² 3p⁶
19	Potassium	1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
20	Calcium	1s² 2s² 2p⁶ 3s² 3p⁶ 4s²