Question

How many electrons are present in the valence shells of the central atoms in the molecules of \(\mathrm{BeCl}_{2}, \mathrm{BF}_{3}\) and \(\mathrm{PCl}_{5}\) ?

Short answer

Answer: The number of electrons present in the valence shells of the central atoms in BeCl2, BF3, and PCl5 are 2, 3, and 5 electrons, respectively.

Step-by-step solution

Finding the Group Number of the Central Atom

Identify the group number of the central atoms in the periodic table. Be is in Group 2, B is in Group 13, and P is in Group 15.

Calculating Valence Electrons for Be in BeCl2

Since Be (beryllium) is in Group 2, it has 2 valence electrons. So, the central atom Be in the BeCl2 molecule has 2 electrons in its valence shell.

Calculating Valence Electrons for B in BF3

B (boron) is in Group 13. It has 3 valence electrons. So, the central atom B in the BF3 molecule has 3 electrons in its valence shell.

Calculating Valence Electrons for P in PCl5

P (phosphorus) is in Group 15, so it has 5 valence electrons. Therefore, the central atom P in the PCl5 molecule has 5 electrons in its valence shell.

Summing Up the Results

In summary, the number of electrons present in the valence shells of the central atoms in BeCl2, BF3 and PCl5 are: - BeCl2: 2 electrons - BF3: 3 electrons - PCl5: 5 electrons.

Key concepts

Central Atoms

In any molecule, the central atom plays a crucial role in defining the structure and properties of the compound. The central atom is typically the least electronegative, meaning it has less tendency to attract electrons compared to surrounding atoms. In the molecules \(\mathrm{BeCl}_2\), \(\mathrm{BF}_3\), and \(\mathrm{PCl}_5\), the central atoms are beryllium (Be), boron (B), and phosphorus (P), respectively. The choice of a central atom usually falls to the atom that can form the greatest number of bonds, as seen with phosphorus (P) in \(\mathrm{PCl}_5\), which forms five bonds. Understanding the identity and characteristics of a central atom is important since it influences the molecular geometry and the behavior of the molecule.

Molecular Geometry

Molecular geometry is the 3D arrangement of atoms around the central atom in a molecule and is determined by the number of bonds and lone pairs on the central atom. It can have a significant impact on the molecule's physical and chemical properties. For example:

• In \(\mathrm{BeCl}_2\), the geometry is linear due to the two bonding pairs of electrons around beryllium.
• \(\mathrm{BF}_3\) has a trigonal planar shape because of the three electron clouds around boron.
• \(\mathrm{PCl}_5\) exhibits a trigonal bipyramidal geometry with five bond pairs around phosphorus.

Each geometric layout dictates how the molecule interacts with other substances and how it behaves in different environments. By predicting the molecular geometry using the number and types of electron pairs, chemists can infer the molecule's reactivity and polarity.

Periodic Table Groups

The periodic table is essential for understanding elements and their interactions. Each element belongs to a group, which is a column in the periodic table, sharing similarities in properties and electron configurations. The group number often equates to the number of valence electrons for elements in that group. For instance:

• Beryllium (Be) is in Group 2, indicating it has 2 valence electrons.
• Boron (B) falls under Group 13, with 3 valence electrons.
• Phosphorus (P) resides in Group 15, containing 5 valence electrons.

Understanding these groups helps in predicting how elements will interact in chemical reactions, including the types of bonds they can form and their general reactivity characteristics.

Electron Configuration

Electron configuration describes the distribution of electrons in an atom's orbitals and is crucial for predicting atomic behavior. Electrons fill orbitals in a specific order based on the atom's energy levels. These configurations can be determined using the periodic table, which acts as a map. For example, beryllium (Be) has an electron configuration of \(1s^2 2s^2\), with two electrons in its outermost shell, contributing to its two valence electrons. Boron (B), with an electron configuration of \(1s^2 2s^2 2p^1\), has three valence electrons. Phosphorus (P) has \(1s^2 2s^2 2p^6 3s^2 3p^3\), which explains its five valence electrons. Knowing how electrons are arranged helps us understand how atoms bond and interact, providing insight into their chemical behavior. Studying electron configurations allows scientists to predict molecular formations and reactivity.