First 20 Elements of the Periodic Table: Names, Symbols & Atomic Numbers

Atomic Numbers And Symbols of The First 20 Elements

First 20 Elements of The Periodic Table

The periodic table is the representation of elements in increasing order of their atomic numbers.

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Name And Symbols Of Elements

The atomic number, element name, or element symbol can all be used to identify elements. A one- or two-letter abbreviation of the name serves as the emblem. Some symbols, on the other hand, allude to old element names. The symbol for sodium for given as Na. This is a reference to the Latin word natrium, which was once used to refer to caustic soda. In Latin, the name of the atomic no of sodium is found to be atrium. Potassium's symbol is K, which is derived from the Latin word kalium, which denoted alkali or potash. An element symbol's initial letter is capitalised. It's lowercase when there's a second letter.

1. Hydrogen

Under normal circumstances, hydrogen is a non-metallic, colourless gas. It transforms into an alkali metal under great pressure. This element has three isotopes, each with a different number of neutrons in its atoms. Protium is the most prevalent isotope. Deuterium and tritium are the other two.

• The atomic number of Hydrogen is 1
• H is its symbol
• It is estimated to have an atomic mass value of 1.008 amu
• H is assigned 1s¹ configuration
• It is a Nonmetal belonging to group 1 and the s-block

2. Helium

• Helium is a light gas with no visible colour.
• The atomic number of Helium is 2
• He is its symbol
• It is estimated to have an atomic mass value of 4.002 amu
• He is assigned 1s² configuration
• It belongs to group 18 and the s-block

3. Lithium

It is a highly reactive solid metal with a silver colour

• The atomic number of Lithium is 3
• Li is its symbol
• It is estimated to have an atomic mass value of 6.94 amu
• Li is assigned [He] 2s¹ configuration
• It is an alkali metal belonging to group 1 and the s-block.

4. Beryllium

It is a solid material with a shiny grey- white appearance

• The atomic number of beryllium is 4
• Be is its symbol
• It is estimated to have an atomic mass value of 9.012 amu
• Be is assigned [He] 2s² configuration
• It is an alkaline earth metal belonging to group 2 and the s-block.

5. Boron

• The atomic number of Boron is 5
• B is its symbol
• It is estimated to have an atomic mass value of 10.81 amu
• B is assigned [He] 2s² 2p¹ configuration
• It is a metalloid belonging to group 13 and the p-block.

6. Carbon

• The atomic number of carbon is 6
• C is its symbol
• It is estimated to have an atomic mass value of 12.011 amu
• C is assigned [He] 2s² 2p² configuration
• It is a metalloid belonging to group 14 and the p-block

7. Nitrogen

• The atomic number of nitrogen is 7
• N is its symbol
• It is estimated to have an atomic mass value of 14.007 amu
• N is assigned [He] 2s² 2p³ configuration
• It belongs to group 15 and the p-block.

8. Oxygen

• The atomic number of oxygen is 8
• O is its symbol
• It is estimated to have an atomic mass value of 16 amu
• O is assigned [He] 2s² 2p⁴ configuration
• It belongs to group 16 and p-block

9. Fluorine

• The atomic number of fluorine is 9
• F is its symbol
• It is estimated to have an atomic mass value of 18.989 amu
• F is assigned [He] 2s² 2p⁵ configuration
• It belongs to group 17 and p-block

10. Neon

• The atomic number of neon is 10
• Ne is its symbol
• It is estimated to have an atomic mass value of 20.179 amu
• N is assigned [He] 2s² 2p⁶ configuration
• It belongs to group 18 and the p-block

11. Sodium

• The atomic number of sodium is 11
• Na is the symbol of sodium
• The Latin name of sodium is Natrium
• It is estimated to have an atomic mass value of 22.989 amu
• F is assigned [Ne] 3s¹ configuration
• It belongs to group 1 and the s-block

12. Magnesium

• The atomic number of magnesium is 12
• Mg is its symbol
• It is estimated to have an atomic mass value of 24.309 amu
• Mg is assigned [Ne] 3s² configuration
• It belongs to group 2 and the s-block

13. Aluminium

• The atomic number of aluminium is 13
• Al is its symbol
• It is estimated to have an atomic mass value of 26.968 amu
• Al is assigned [Ne] 3s² 3p¹ configuration
• It belongs to group 13 and the p-block

14. Silicon

• The atomic number of Silicon is 14
• Si is its symbol
• It is estimated to have an atomic mass value of 28.085 amu
• Si is assigned [Ne] 3s² 3p² configuration
• It belongs to group 14 and the p-block.

15. Phosphorus

• The atomic number of Phosphorus is 15
• P is its symbol
• It is estimated to have an atomic mass value of 30.9737 amu
• P is assigned [Ne] 3s² 3p³ configuration
• It belongs to group 15 and the p-block

16. Sulphur

• The atomic number of Sulfer is 16
• S is its symbol
• It is estimated to have an atomic mass value of 32.09 amu
• S is assigned [Ne] 3s² 3p⁴ configuration
• It belongs to group 16 and the p-block

17. Chlorine

• The atomic number of Chlorine is 17.
• Cl is its symbol
• It is estimated to have an atomic mass value of 35.45 amu
• Cl is assigned [Ne] 3s² 3p⁵ configuration
• It belongs to group 17 and the p-block

18. Argon

• The atomic number of argon is 18
• Ar is its symbol
• It is estimated to have an atomic mass value of 39.948 amu
• Ar is assigned [Ne] 3s² 3p⁶ configuration
• It belongs to group 18 and the p-block

19. Potassium

• The atomic number of Potassium is 19
• The Latin name of potassium is found to be Kalium
• K is its symbol
• It is estimated to have an atomic mass value of 39.093 amu
• K is assigned [Ar] 4s¹ configuration
• It belongs to group 1 and the s-block

20. Calcium

• The atomic number of Calcium is 20.
• Ca is its symbol
• It is estimated to have an atomic mass value of 40.10 amu
• Ca is assigned [Ar] 4s² configuration
• It belongs to group 14 and the s-block

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Some Solved Examples

Question 1: Choose the correct option:

1) (correct)The period of the element is determined by its highest shell

2)The period of the element is determined by its last orbital

3)The period of the element is determined by its valence shell electrons

4)The period of the element is determined by its valency

Solution:

The period of the element is determined by its highest shell.

Hence, the answer is option (1).

Question 2: Which pair of atomic numbers represents s-block elements

1)7,15

2)6,12

3)9,17

4) (correct)3,12

Solution:

Out of the given elements, Z=3 (Li) and Z = 12 (Mg) belong to the s Block of the periodic table.

Hence, the answer is option (4).

Question 3: Newland’s octet law was successful in arranging:

1)Heavier elements

2) (correct)Lighter elements

3)Both

4)None

Solution:

Newland’s octet law was successful in arranging lighter elements. After calcium, this law did not work as expected.

Hence, the answer is option (2).

Question 4: Which of the following pairs of elements among the first 20 elements have the same number of unpaired electrons in their ground-state electronic configurations?

1) N and P
2) O and S
3) C and Si
4) All of these

Solution:

$N(Z=7): 1 s^2 2 s^2 2 p^3 \rightarrow 3$ unpaired electrons
$P(Z=15):[N e] 3 s^2 3 p^3 \rightarrow 3$ unpaired electrons
$\mathrm{O}(\mathrm{Z}=8): 1 \mathrm{~s}^2 2 \mathrm{~s}^2 2 \mathrm{p}^4 \rightarrow 2$ unpaired electrons
$\mathrm{S}(\mathrm{Z}=16):[\mathrm{Ne}] 3 \mathrm{~s}^2 3 \mathrm{p}^4 \rightarrow 2$ unpaired electrons
$\mathrm{C}(\mathrm{Z}=6): 1 \mathrm{~s}^2 2 \mathrm{~s}^2 2 \mathrm{p}^2 \rightarrow 2$ unpaired electrons
Si $(Z=14):[\mathrm{Ne}] 3 s^2 3 p^2 \rightarrow 2$ unpaired electrons

Therefore, all the given pairs have the same number of unpaired electrons.

Hence, the correct answer is option (4)

Question 5: Among the first 20 elements, how many elements have filled valence shells in their ground state?

1) 3
2) 4
3) 5
4) 6

Solution:

Elements with completely filled valence shells are the noble gases:

$\begin{aligned} & \mathrm{He}\left(1 s^2\right) \\ & \mathrm{Ne}\left(2 s^2 2 p^6\right) \\ & \mathrm{Ar}\left(3 s^2 3 p^6\right)\end{aligned}$

Only these three elements among the first 20 elements have completely filled outermost shells.

Hence, the correct answer is option (1)

Practice More Questions From The link given below

For more questions to practice, the following MCQs will help in the preparation for competitive examinations