Problem 56 - Chemistry: An Atoms-Focused Approach

Question

Which metal do you expect to have the higher melting point- Al or Na? Explain your answer.

Step-by-Step Solution

Answer

Answer: Aluminum (Al) has a higher melting point compared to Sodium (Na) due to its stronger and more extensive metallic bonding, which is a result of a greater number of valence electrons participating in the bond.

Step 1: Analyze the position of Al and Na in the periodic table

Aluminum (Al) has an atomic number of 13, which belongs to Group 13 and Period 3 in the periodic table. Sodium (Na) has an atomic number of 11 and is found in Group 1 and Period 3. In general, metals in lower group numbers have lower melting points than those with higher group numbers.

Step 2: Examine the electronic configuration of Al and Na

The electronic configuration of Aluminum (Al) is [Ne]3s²3p¹, while Sodium (Na) has an electronic configuration of [Ne]3s¹. The number of valence electrons in the outermost shell for Al is 3, while Na has only 1 valence electron.

Step 3: Understand the metallic bonding involved

Metals form metallic bonds in which valence electrons are shared among all atoms in the metal. In metallic bonding, metal atoms release their valence electrons, forming a "sea" of delocalized electrons. These delocalized electrons are attracted to the positively charged metal ions, creating a strong bond between them.

Step 4: Compare the strength of metallic bonds in Al and Na

Aluminum (Al) has three valence electrons that participate in metallic bonding, while Sodium (Na) has only one valence electron. Due to the greater number of valence electrons being shared among the atoms in Aluminum, the metallic bonding is expected to be stronger and more extensive in Aluminum compared to Sodium.

Step 5: Determine the melting points based on the metallic bond strength

Stronger metallic bonding leads to a higher melting point. Since Aluminum (Al) has stronger metallic bonding due to the greater number of valence electrons participating in the bonding, it is expected to have a higher melting point than Sodium (Na).

Step 6: Conclusion

Aluminum (Al) is expected to have a higher melting point compared to Sodium (Na) due to its stronger and more extensive metallic bonding, which is a result of a greater number of valence electrons participating in the bond.

Key Concepts

Periodic Table

The periodic table is like a map for chemists. It organizes all known chemical elements based on their atomic number, electron configuration, and recurring chemical properties. Elements are arranged in rows called periods and columns known as groups. Each placement gives you clues about an element's characteristics.

• Group numbers tell you how many valence electrons an atom has. For example, elements in Group 1 have 1 valence electron, while Group 13 elements have 3 valence electrons.
• Period numbers indicate the number of electron shells an atom possesses. Both Sodium and Aluminum are in Period 3, meaning they have three electron shells.
• Metals typically occur on the left side and central part of the periodic table. Non-metals are mostly found on the right.

Each element's position can give insight into its melting point, reactivity, and other properties. Generally, elements in lower groups have more metallic characteristics and lower melting points.

Valence Electrons

Valence electrons are the outermost electrons of an atom. They play a key role in chemical bonding and properties of the element. The number of valence electrons impacts how atoms bond with each other, which in turn affects physical properties such as melting points.

• Aluminum (Al) has three valence electrons, found in the 3s and 3p orbitals.
• Sodium (Na), on the other hand, has only one valence electron in the 3s orbital.

In metallic bonding, these valence electrons are not tied to one atom but are free to move around, forming what is known as a 'sea of electrons.' The more valence electrons present, the stronger the metallic bond usually is. This is because there are more electrons to share, enhancing the attraction between the positive metal ions and the delocalized electrons. Thus, stronger bonds require more energy to break, resulting in higher melting points.

Melting Points

The melting point of a metal is the temperature at which it transitions from a solid to a liquid. It's an indicator of the strength of the bonds holding the metal atoms together. In metals, these are primarily metallic bonds formed by the sea of electrons.

• Aluminum (Al) has a high melting point because of its strong metallic bonds, a result of its three valence electrons shared in bonding.
• Sodium (Na) has a notably lower melting point due to its weaker metallic bonds, derived from having only a single valence electron participating in bonding.

Factors influencing the melting point include the number of valence electrons, the density of packing of metal ions, and atomic size. Larger metal ions and a lower number of bonding electrons typically lead to weaker metallic bonds and thus lower melting points. Therefore, with more valence electrons actively involved in bonding, Aluminum creates a more rigid structure needing higher temperatures to melt compared to Sodium.