[Chemistry Class Notes] First 20 Elements Pdf for Exam

The atomic number and symbols are important in chemistry. The element symbol is a one- or two-letter abbreviation of the name of the element. While writing long chemical equations, we need to write a short form of the compounds and elements that time these symbols are very useful. The atomic number of elements gives an idea about the atomic structure of elements, such as how many electrons and protons that particular element has. The first 20 elements of the periodic table are given in the figure below.

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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.

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

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

Before knowing the importance of an atomic number of elements take a look at the following definitions.

• 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.

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.

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 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.

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.

Conclusion

Hence knowing about the first twenty elements of the periodic table is the basic step in order to gain knowledge about all the elements. This article will develop an understanding of atomic numbers and symbols of elements.