Question

The clectronic configuration of two elements \(\Lambda\) and \(B\) are respectively \(1 s^{2} 2 s^{2} 2 p^{6}\) and \(1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6}\). Thereforc, their positions in the periodic table are (1) A after B (2) A before B (3) A above B (4) A below B

Short answer

(4) A below B

Step-by-step solution

Identify the Electron Configuration of Elements A and B

Element A has the electron configuration: \( 1s^2 2s^2 2p^6 \)Element B has the electron configuration: \( 1s^2 2s^2 2p^6 3s^2 3p^6 \)

Determine the Total Number of Electrons for Each Element

Count the total number of electrons in each configuration.Element A: \( 2 + 2 + 6 = 10 \) electrons (Neon)Element B: \( 2 + 2 + 6 + 2 + 6 = 18 \) electrons (Argon)

Locate the Elements on the Periodic Table

Neon (A) is located in Period 2, Group 18.Argon (B) is located in Period 3, Group 18.

Compare the Positions of A and B

Neon (A) is in Period 2, directly above Argon (B) which is in Period 3, both in Group 18.

Key concepts

Electron Configuration

Electron configuration is a method to symbolize the distribution of electrons in an atom's orbitals. It helps in understanding the arrangement of electrons in shell and subshell levels. For example, element A's configuration is given as 1s² 2s² 2p⁶. Breaking this down:

• The '1s' stands for the first energy level and 's' orbital, which can hold a maximum of 2 electrons. Here, it has 2 electrons.
• The '2s' stands for the second energy level and another 's' orbital, again holding 2 electrons.
• The '2p' stands for the second energy level and 'p' orbital, with a maximum capacity of 6 electrons, which it is fully filled here.

Element B's electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶. This follows similar principles, but it includes a third energy level with 's' and 'p' orbital electrons.
Identifying the electron configuration helps in placing elements correctly on the periodic table.

Periodic Table

The periodic table is a systematic arrangement of chemical elements based on their atomic numbers, electron configurations, and recurring chemical properties. Elements are arranged in rows (periods) and columns (groups or families). Elements within the same group have similar chemical behaviors because their valence electrons are similarly arranged. For instance:

• Period number tells us how many electron shells an atom possesses. Neon, being in period 2, has electrons in 2 shells.
• Group number relates to the number of valence electrons. Group 18 elements like Neon and Argon have a full outer shell of 8 electrons (except Helium).

The periodic table makes it easier to understand trends such as atomic radius, ionization energy, and electronegativity.

Element Positioning

Element positioning in the periodic table depends on electron configuration and atomic number. By understanding the electron configuration, we can determine the period and group in which an element belongs. For example: Neon is placed in Period 2, Group 18 because it has two electron shells (1s² 2s² 2p⁶) and a full outer shell. Argon is in Period 3, Group 18, as it has three electron shells (1s² 2s² 2p⁶ 3s² 3p⁶) and also a full outer shell.
In the given exercise, comparing the positions of Neon (10 electrons) and Argon (18 electrons) in the periodic table was key to determining that:

• Neon is above Argon because it is in the second period and Argon is in the third.

Elements in the same group share similar properties, meaning they follow the same behavior trends.

Neon

Neon is a noble gas with the atomic number 10, which means it has 10 protons and usually 10 electrons. It is represented by the symbol Ne. In its electron configuration (1s² 2s² 2p⁶), Neon has a full outer shell, making it very stable and chemically inert.
Noble gases, like Neon, do not easily form compounds because they already have a stable electron configuration. This property lands Neon in Group 18 of the periodic table. Some interesting facts about Neon include:

• It is used in neon signs due to its ability to emit bright light when electrically charged.
• Neon is the fifth most abundant element in the universe but quite rare on Earth.

The full electron configuration explains its lack of reactivity and important positioning in the periodic table.

Argon

Argon, represented by the symbol Ar, is another noble gas with the atomic number 18. Its electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶, indicating a total of 18 electrons.
The presence of a full outer shell of electrons explains why Argon is also chemically inert and placed in Group 18. Key uses and properties include:

• About 1% of Earth's atmosphere is Argon, making it the third most abundant gas in our atmosphere.
• It is widely used in industries for providing an inert atmosphere, like in welding and preserving historical documents.

Understanding Argon's electron configuration is crucial for explaining its placement on the periodic table just below Neon in Period 3, indicating it has three electron shells.
The stable electron configuration positions Argon as an essential part of the noble gases series.