What are the First 20 Elements of the Periodic Table?

The first 20 elements of the periodic table, which have atomic numbers 1-20, are listed below.

Atomic No

Name

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

Sulfur

S

17

Chlorine

Cl

18

Argon

Ar

19

Potassium

K

20

Calcium

Ca


Each element consists of distinct properties owing to their atomic number, atomic mass, electronic configuration, electronegativity, electron gain enthalpy, etc.


Importance of The Atomic Number of An Element in A Periodic Table

The atomic number of an element in the periodic table provides us with the following information:

  • Gives an idea about the number of protons in the nucleus of an atom

  • The number of electrons surrounding the nucleus in a neutral atom.

In other words, we can say that the atomic number is equal to the charge on the nucleus. Hence, it is also similar to the number of protons in the nucleus. It is numerically equal to the number of electrons in a neutral atom.

Let's try to understand it further with the example of Oxygen. Oxygen has an atomic number of 8. This implies that in the neutral state, the number of protons in the nucleus is 8. The number of electrons is 8. Similarly, in sodium, which has an atomic number of 11, the sodium atom's nucleus consists of 11 protons. It has 11 electrons surrounding the nucleus. As we know that the atomic number is equal to the number of electrons, we can easily predict the atom's electronic configuration by merely knowing its atomic number.


Atomic number

The atomic number tells us how many protons are there in the nucleus.

Protons - It is a subatomic (occurring within an atom) particle. It has a positive charge. It resides in the nucleus of an atom of the element.

Neutrons - It is also a subatomic particle. Neutrons have a neutral charge. A neutron weighs a little bit higher than a proton. Neutrons, along with the protons, add up to form the nucleus of the atom.

Electrons - Electrons are also subatomic. Electrons tend to orbit around the nucleus. The electrons are negatively charged. The size of the electrons is smaller than that of the nucleus. Electrons have an equal charge as the proton, but with a negative sign. The mass of an electron is almost 1/1836 times the mass of a proton.


How Does The Periodic Table Help?

The periodic table of the elements in Chemistry is the organized arrangements of all known elements in the order of their increasing atomic number represented by the number of protons of an atom.

Elements situated in the same column consist of similar properties and are denoted as groups. Elements located in the same row are called periods and consist of the equal highest unexcited electron energy levels. The periodic table can also provide us with information on an element's atomic weight and the usual charge. All this data, and much more, compiled into one universal, comprehensive reference table makes the periodic table important.


Mass Number

It is denoted by A.

When we add up the number of protons and the number of neutrons of the atom, it gives us the element's mass number. Neutrons and protons are collectively called nucleons because they are present in the nucleus itself. Now, let us look at a few examples. Oxygen has 8 protons, while the number of neutrons it has is also 8. This implies that the mass number of Oxygen is 8+8, that is 16.

Since the mass of an electron is approximately negligible, the element's atomic mass is almost equal to its mass number. Atomic mass is measured in terms of atomic mass unit. It is also called Dalton, denoted by D.


Noble Gases in the First 20 Elements of the Periodic Table

First, we need to know what noble gases are.

Noble gases are also called inert gases. Noble gases are situated in the 18th group of the periodic table. These are known to be the least reactive or extremely non-reactive. The noble gases were characterized later than other elements.

So, in the first 20 elements, there are three noble gases, namely, Helium (He), Neon (Ne), and Argon (Ar). Helium has an atomic number 2, Neon has an atomic number of 10, while Argon has an atomic number of 18.

FAQs (Frequently Asked Questions)

1. What are Isotopes?

Isotopes are the variation of a specific element which differs in the number of neutrons and subsequently in the number of nucleons. However, it is essential to note that all the isotopes of a particular element have the same proton number. The difference lies only in the number of neutrons, hence, in the number of nucleons.

2. Why are Sodium and Potassium Symbolized as Na and K, Respectively?

Symbol for sodium is derived from its previous name, 'Natrium'. Hence, the symbol of 'Na' is used. Similarly, the medieval Latin name for potassium was 'Kalium'. Thus, the symbol of potassium is 'K'.  

3. How are the first 20 elements of the periodic table useful for us?

Some of the elements of the first 20 elements of the periodic table are very much helpful for our daily life such as:

  • Oxygen (O)- Oxygen has an essential role in respiration. Respiration is the energy-producing mechanism that dictates the metabolisms of most of the living organisms. Humans, along with many other beings, require oxygen for breathing. Oxygen is generated during the process of photosynthesis in plants and different types of microorganisms.

  • Carbon (C)- Carbon consists of 18% of the human body. Protein, sugar and other essential compounds including glucose contain carbon. Fossil fuels, like petroleum, CNG etc. also contain carbon.

  • Aluminium (Al)- Aluminium, being malleable and soft, is used in the making of various products like utensils, aeroplane parts, window frames etc. 

  • Silicon (Si) - Silicon, a semiconductor, is used in computer chips.

  • Phosphorus (P)- Phosphorus is used in the military to make weapons (white phosphorus). Phosphorus is an integral part of ATP, the energy currency of our body.

  • Calcium (Ca)- Calcium helps in maintaining bone strength.