Problem 41 - A Complete Resource Book in Chemistry for JEE Main

Question

The atomic number of \(\mathrm{Ni}\) and \(\mathrm{Cu}\) are 28 and 29 respectively. The electronic configuration \(1 \mathrm{~s}^{2} 2 \mathrm{~s}^{2} 2 \mathrm{p}^{6} 3 \mathrm{~s}^{2} 3 \mathrm{p}^{6}\) \(3 \mathrm{~d}^{10}\) represents (a) \(\mathrm{Cu}^{+}\) (b) \(\mathrm{Cu}^{2+}\) (c) \(\mathrm{Ni}^{2+}\) (d) \(\mathrm{Ni}\)

Step-by-Step Solution

Answer

The electronic configuration represents neutral Ni.

Step 1: Identify Total Electrons in Configuration

First, find the total number of electrons in the given electronic configuration. Count all the electrons from each subshell in the configuration: \(1s^2\), \(2s^2\), \(2p^6\), \(3s^2\), \(3p^6\), and \(3d^{10}\). Adding these electrons gives us \(2 + 2 + 6 + 2 + 6 + 10 = 28\) electrons.

Step 2: Determine the Atomic Number

The electronic configuration indicates a total of 28 electrons, signifying an atomic number of 28 (since for a neutral atom, atomic number equals the number of electrons). Therefore, this is the atomic number of Ni (Nickel).

Step 3: Identify the Ion or Atom

Since the configuration corresponds to 28 electrons which is the atomic number of Ni, the possible species can be either neutral Ni or a Ni ion. The given electronic configuration matches exactly with the configuration of a Ni atom, which has 28 electrons and no electrons removed or added, so the electronic configuration represents neutral Ni.

Key Concepts

Atomic Number

The atomic number is a basic concept in chemistry and physics, serving as a unique identifier for chemical elements. It represents the number of protons found in the nucleus of an atom, which is also equal to the number of electrons in a neutral atom.
This invaluable property defines the element's identity and determines its position in the periodic table. For each element:

• The atomic number increases by one as you move from one element to the next in the periodic table.
• It is the key factor in the arrangement of elements, ensuring the periodic trends are consistent.
• Elements with the same atomic number share similar chemical properties because they have identical electronic structures.

In the given exercise, knowing that \(Ni\) (Nickel) has an atomic number of 28 allows us to deduce its electronic configuration and infer its behavior in different chemical environments.

Nickel

Nickel is a chemical element that belongs to the transition metals group and is situated in the 10th group of the periodic table. With an atomic number of 28, Nickel exhibits several interesting properties:

• It possesses a silvery-white appearance and is known for its excellent resistance to corrosion and its overall stability in numerous conditions.
• The electronic configuration of Nickel, when neutral, is \(1s^2 2s^2 2p^6 3s^2 3p^6 3d^8 4s^2\). This configuration determines how Nickel can participate in bonding and reactions with other elements.
• As a transition metal, Nickel can form various oxidation states, although the most common states are +2 and +3.

In the context of the exercise, the given electronic configuration matched that of neutral Nickel, affirming its identity based on the count of 28 electrons.

Ion Identification

Ion identification is vital in understanding the varying chemical behaviors of elements and compounds. Ions are formed when atoms gain or lose electrons to achieve a stable electron configuration.
In general:

• Cations are positively charged ions formed by the loss of electrons.
• Anions are negatively charged ions formed by the gain of electrons.

The task of identifying ions from electronic configurations involves comparing the number of electrons with the neutral atomic number of the element. If the electron count differs from the neutral atom, the atom has either gained or lost electrons, indicating it is not neutral but an ion.
In the given exercise, the electronic configuration corresponded to 28 electrons, exactly matching that of neutral Nickel ( Ni). Therefore, no ion formation is indicated, ruling out any consideration of Ni as a Ni ²⁺ ion or any other ion state, based on the provided configuration.