Problem 29 - A Complete Resource Book in Chemistry for JEE Main

Question

An atom has electronic configuration: Is \(2 \mathrm{~s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{~s}^{2}\) \(3 \mathrm{p}^{6} 3 \mathrm{~d}^{3} 4 \mathrm{~s}^{2}\), you will place it in (a) V group (b) \(\mathrm{XV}\) group (c) II group (d) III group

Step-by-Step Solution

Answer

The atom is in group V.

Step 1: Identify the Element Using the Electron Configuration

To identify the element, count the total number of electrons based on the given electronic configuration. The configuration is: - $1s^2$ - $2s^2$ - $2p^6$ - $3s^2$ - $3p^6$ - $3d^3$ - $4s^2$ So, the total number of electrons is $2+2+6+2+6+3+2 = 23$. An atom with 23 electrons is Vanadium (V).

Step 2: Determine the Group Based on Electron Configuration

For the transition elements, the group number can be deduced from the number of electrons in the outermost $d$ and $s$ orbitals. Here, look at the $3d$ and $4s$ orbitals: - $3d^3$ - $4s^2$ Add the electrons in $3d$ and $4s$: $3 + 2 = 5$. Hence, the element is placed in group V.

Key Concepts

Electron Configuration Interpretation

In chemistry, an electron configuration refers to how electrons are distributed across an atom's orbitals. It helps us understand an atom's chemical behavior. Electrons fill orbitals in a specific order based on increasing energy levels. This process is guided by the "Aufbau Principle." For example, the given configuration:

• \(1s^2\)
• \(2s^2\)
• \(2p^6\)
• \(3s^2\)
• \(3p^6\)
• \(3d^3\)
• \(4s^2\)

shows that electrons fill the lowest energy orbitals first, moving to higher energy states as they progress. When you add the exponents (superscripts) in this electron configuration, you get the total number of electrons in the atom, which corresponds to the element's atomic number.

Transition Elements

Transition elements are a group of metals found in the central block of the periodic table, specifically in groups 3 to 12. These elements are known for their ability to form various oxidation states because they have incomplete d-orbitals. In the example provided, Vanadium (V) is a transition element. These elements are characterized by:

• Having partially filled d subshells.
• Exhibiting high tensile strength and melting points.
• Able to form complex ions with different charges.
• Displaying various magnetic properties due to unpaired d electrons.

The properties of transition elements, like their colored compounds and ability to act as catalysts, are directly linked to the electronic configurations of their d-orbitals.

Atomic Structure

Atomic structure refers to the arrangement of subatomic particles—protons, neutrons, and electrons—within an atom. The protons and neutrons reside in the nucleus, while electrons occupy orbitals around the nucleus. The number of positively charged protons defines the atomic number, determining the element's identity. For example, an atom with 23 protons is always Vanadium, regardless of the number of neutrons or electrons. Atomic structure determines an element's placement on the periodic table, dictating its properties and chemical behavior. These structures are pivotal in understanding reactivity and bonding capabilities of different elements.

Orbital Notation

Orbital notation is a visual representation of where electrons exist within an atom's orbitals. It provides insight into the spatial distribution of electrons. Unlike electron configurations that use numbers and letters, orbital notation uses boxes (or lines) and arrows to signify electron spins.For instance, for the element Vanadium, the configuration \(3d^3\) indicates three electrons in the d subshell. In orbital notation, three separate boxes would have one arrow each, pointing up (or down), representing unpaired electron spins.

• This representation helps understand concepts like electron pairing and magnetic properties.
• It also showcases Hund's Rule: every orbital in a sublevel is singly occupied before being doubly occupied.
• Helps in visualizing possible unpaired electrons, crucial for understanding bonding and reactivity.

Overall, orbital notation provides a clearer image of electron arrangements, making it easier to study the atomic interactions.