Problem 1 - A Complete Resource Book in Chemistry for JEE Main

Question

How many \(\mathrm{e}^{-}\)are present in p-sub-orbits in \(\mathrm{Zn}\)-atom? (a) 2 (b) 6 (c) 12 (d) 18

Step-by-Step Solution

Answer

Zn has 12 electrons in p-sub-orbits.

Step 1: Determine the Electron Configuration of Zinc

The atomic number of zinc (Zn) is 30, which means it has 30 electrons. The electron configuration of Zn is \([ \mathrm{Ar} ]\ 3d^{10} 4s^{2}\). It concludes with the 3d and 4s orbitals.

Step 2: Identify the p-sub-orbits in Electron Configuration

In the given electron configuration of zinc, \([ \mathrm{Ar} ]\) includes the 1s, 2s, 2p, 3s, and 3p orbitals. The p-sub-orbits here include 2p and 3p.

Step 3: Count Electrons in p-sub-orbits

The 2p orbital contains 6 electrons and the 3p orbital also contains 6 electrons. Summing these gives a total of 12 electrons in p-sub-orbits.

Key Concepts

Zinc Atom

Zinc is a chemical element with the symbol Zn and an atomic number of 30, which means it has a total of 30 electrons when neutral. These electrons are distributed across different energy levels and orbitals within the atom. Understanding the arrangement of electrons in a zinc atom, known as its electron configuration, is crucial for predicting how it will chemically react with other elements. For zinc, the electron configuration is \([ \mathrm{Ar} ]\ 3d^{10} 4s^{2}\). This indicates that zinc's electrons fill up to the 3d and 4s sublevels.

p Orbitals

In chemistry, 'p orbitals' refer to the set of orbitals in the second and higher principal energy levels that can hold up to 6 electrons. These are shaped like a dumbbell and can be oriented in three different spatial orientations: \(p_x, p_y,\) and \(p_z\). Each orientation can accommodate a pair of electrons:

• p orbitals are present from the second principal energy level ()
• They are found in every other level, starting from \(n = 2\)

In a zinc atom's electron configuration, p orbitals are found in the \(\mathrm{[Ar]}\) configuration, where \(2p\) and \(3p\) orbitals each hold 6 electrons.

Atomic Orbitals

Atomic orbitals describe regions around the nucleus of an atom where electrons are likely to be found. Each orbital can hold a specific number of electrons. The primary types of orbitals include s, p, d, and f:

• s orbitals: spherical, holding up to 2 electrons
• p orbitals: dumbbell-shaped, holding up to 6 electrons
• d orbitals: more complex, holding up to 10 electrons
• f orbitals: even more complex, holding up to 14 electrons

In the zinc atom, the \(3d\) orbital, which can accommodate up to 10 electrons, is fully occupied and completed before the \(4s\) orbital.

Electron Counting

Determining the number of electrons in each orbital type involves the concept of electron counting. In zinc, we start by looking at the core and valence electrons:

• Core electrons are found in inner orbitals
• Valence electrons are located in the outermost orbitals

To find the number of electrons in p orbitals for zinc, we go through its electron configuration: \([ \mathrm{Ar} ]\ 3d^{10} 4s^{2}\), where \(\mathrm{[Ar]}\) represents \(1s^2 2s^2 2p^6 3s^2 3p^6\). The p orbitals (2p and 3p) collectively contain 12 electrons.