Question

Write a Lewis formula for each of the following molecules. (a) \(\mathrm{N}_{2} \mathrm{H}_{2}\) (c) AsF \(_{3}\) (e) \(\mathrm{CO}\) (b) \(\mathrm{CS}_{2}\) (d) \(\mathrm{CO}_{2}\)

Short answer

The Lewis structures for \(\mathrm{N}_{2} \mathrm{H}_{2}\), \(\mathrm{AsF}_{3}\), \(\mathrm{CO}\), \(\mathrm{CS}_{2}\), and \(\mathrm{CO}_{2}\) have been generated. Each molecule's structure takes into account the total number of valence electrons, as well as the least electronegative atom, which is typically in the center, and bound to the other atoms.

Step-by-step solution

Determination of Valence Electrons

The first step involves determining the valence electrons for each atom in the molecule. We know that Nitrogen contributes 5 electrons, Hydrogen contributes 1 each, Carbon 4, Oxygen 6, Sulfur 6, and As (Arsenic) and F (Fluorine) contribute 5 and 7 respectively.

Lewis Structure for N2H2

Firstly, let's assign the Lewis structure for \(\mathrm{N}_{2} \mathrm{H}_{2}\). The total number of valence electrons would be 10. Position the Nitrogen atoms next to each other and then place each Hydrogen atom next to each Nitrogen atom. Draw lines to represent the bonds and allocate the remaining electrons appropriately.

Lewis Structure for AsF3

For \(\mathrm{AsF}_{3}\), all the Fluorine atoms will be surrounding the As atom. The total valence electrons for this molecule is 26. After linking As and F with single bonds, the remaining electrons would be allocated to each Fluorine atom.

Lewis Structure for CO

For \(\mathrm{CO}\), there are 10 valence electrons. Link each Carbon atom to the Oxygen atom with a triple bond and allocate the remaining electrons on the Oxygen atom.

Lewis Structure for CS2

In \(\mathrm{CS}_{2}\), Carbon is in the middle, surrounded by the Sulfur atoms. With 16 valence electrons, after linking each Carbon atom to each Sulfur atom with a double bond, the remaining electrons are allocated to the Sulfur atoms.

Lewis Structure for CO2

Finally, in \(\mathrm{CO}_{2}\), there are 16 valence electrons. Carbon is in the middle and is linked to each Oxygen atom with a double bond.

Key concepts

Valence Electrons

Valence electrons are the outermost electrons of an atom and are crucial for understanding chemical reactivity and bonding. They are responsible for the formation of bonds between atoms. The number of valence electrons effectively determines how an atom will interact with others.
For instance, in the provided molecules, recognizing the valence electrons involves looking up their values for each element:

• Nitrogen (N) has 5 valence electrons,
• Carbon (C) has 4,
• Oxygen (O) has 6,
• Sulfur (S) also has 6,
• Arsenic (As) has 5,
• and Fluorine (F) carries 7 valence electrons.

Knowing the number of valence electrons lays the foundation to draw correct Lewis structures.
Each electron participates in bonding with a neighboring atom or remains as a lone pair, providing complete understanding of the molecule's geometry and potential reactivity.

Chemical Bonds

Chemical bonds are interactions that hold atoms together in compounds. These can be characterized mainly as ionic or covalent bonds. In Lewis structures, we typically focus on covalent bonds, where atoms share electrons to achieve stable electron configurations.
For example, in the molecule \(\mathrm{CO}\) (carbon monoxide), the carbon and oxygen atoms form a triple covalent bond, sharing three pairs of electrons for stability.
Another type is the double bond as seen in \(\mathrm{CO}_{2}\) (carbon dioxide), where each carbon-oxygen connection involves two pairs of shared electrons.
Ultiamtely, forming these bonds helps atoms achieve a full outer electron shell, generally mimicking the nearest noble gas electron configuration. It's this arrangement that gives molecules stability in achieving lower potential energy through electron pairing and sharing.

Electron Configuration

Electron configuration describes how electrons are distributed within an atom's orbital, influencing both the chemical behavior and how bonds are formed.
It is often referred to using notation that specifies the energy levels (n) and types of orbitals (s, p, d, f).
These configurations help predict the number of valence electrons.
For instance, consider nitrogen in \(\mathrm{N}_{2} \mathrm{H}_{2}\): it has an electron configuration of \[1s^{2} 2s^{2} 2p^{3}.\]
Here, the 2s and 2p orbitals account for the 5 valence electrons used in bonding.
Understanding this concept is vital as it explains both the ability of atoms to form multiple bond types and their interactions in multi-atom compounds, much like the provided molecules, in which the distribution is crucial for predicting molecule shape and bond angles.