Problem 2 - General Chemistry: Principles and Modern Applications

Question

Fluorine is able to stabilize elements in very high oxidation states. For each of the elements \(\mathrm{Na}, \mathrm{Mg}, \mathrm{Al}, \mathrm{Si}\) P, S, and Cl, give the formula of the highest-order fluoride that is known to exist. Then, describe the variation in bonding that occurs as we move from left to right across the period.

Step-by-Step Solution

Answer

The highest-order fluorides of given elements which are known to exist are \( \mathrm{NaF}, \mathrm{MgF_2}, \mathrm{AlF_3}, \mathrm{SiF_4}, \mathrm{PF_5}, \mathrm{SF_6}, \mathrm{ClF_7} \). As we move from left to right across the period, the number of bonds that an element forms with Fluorine increases, signifying the increase in available valence electrons for bonding.

Step 1: Identifying highest order fluorides

The highest-order fluorides that exist for the given elements are \( \mathrm{NaF}, \mathrm{MgF_2}, \mathrm{AlF_3}, \mathrm{SiF_4}, \mathrm{PF_5}, \mathrm{SF_6}, \mathrm{ClF_7} \). This means that Sodium (Na) can form one bond with Fluorine (F), Magnesium (Mg) can form two bonds, Aluminium (Al) can form three, Silicon (Si) can form four, Phosphorus (P) can form five, Sulfur (S) can form six, and Chlorine (Cl) can form seven.

Step 2: Describing Variation in Bonding

As we move from left to right across the period in the Periodic Table, the number of bonds an element can form with Fluorine increases. This is because the number of available valence electrons for bonding increases. Sodium (Na) is in Group 1 and has one valence electron, hence it forms one bond. Magnesium (Mg) is in Group 2 and can form two bonds, and so forth. Silicon (Si) is in Group 4 and forms four bonds, Phosphorus (P) is in Group 5 and forms five bonds, Sulfur (S) is in Group 6 and forms six bonds, and Chlorine (Cl) is in Group 7 and forms seven bonds.

Key Concepts

Oxidation States

In chemistry, oxidation states help us understand how many electrons an atom can gain, lose, or share when forming compounds. Fluorine is exceptional in stabilizing high oxidation states. This is because fluorine is highly electronegative, meaning it strongly attracts electrons.

When we talk about oxidation states, think about sodium (Na) forming NaF, where sodium has an oxidation state of +1. Then, if we look at chlorine (Cl) forming ClF even 7, chlorine is in the +7 oxidation state. This shows fluorine's ability to stabilize substantially varying oxidation states across different elements.

• Sodium (Na) +1
• Magnesium (Mg) +2
• Aluminum (Al) +3
• Silicon (Si) +4
• Phosphorus (P) +5
• Sulfur (S) +6
• Chlorine (Cl) +7

These oxidation states are crucial for predicting how these elements will interact with fluorine.

Periodic Table Trends

As we move from left to right across a period in the Periodic Table, we can notice a fascinating trend in oxidation states and electron configuration. Elements have an increasing number of valence electrons available for bonding.

• Sodium is in Group 1 and has 1 valence electron, bonding with one fluorine atom.
• Magnesium in Group 2 has 2 valence electrons, bonding with two fluorine atoms.
• This continues up to Chlorine in Group 7, bonding with seven fluorine atoms.

This trend shows how chemical reactivity and bonding capacity increase across a period. The elements become more adept at forming complex compounds.

Chemical Bonding

Chemical bonding describes how atoms connect to form molecules. In the case of highest-order fluorides, we see different types of bonding based on element positions in the Periodic Table.

As we move across the period, these bonds involve differing numbers of shared electrons. For example:

NaF involves ionic bonding, where electrons are transferred from sodium to fluorine.
For MgF even 2 and AlF even 3, a mix of ionic and covalent bonding occurs.

By the time we reach SiF even 4, PF even 5, SF even 6, and ClF even 7, covalent bonding dominates, with shared pairs of electrons leading to stronger directional bonds.

• Ionic bonding is common toward the left with elements having fewer valence electrons.
• Covalent bonding becomes more prevalent as we move right and elements have more valence electrons.

This variation illustrates the complexity and diversity of chemical bonding as influenced by fluorine's interaction with these elements.