Question

For each of the following pairs, which element will have the greater metallic character: (a) Li or Be, (b) Li or Na, (c) Sn or \(\mathrm{P}_{\text {, }}\) (d) \(\mathrm{Al}\) or \(\mathrm{B}\) ?

Short answer

(a) Li has a greater metallic character than Be. (b) Na has a greater metallic character than Li. (c) Sn has a greater metallic character than P. (d) Al has a greater metallic character than B.

Step-by-step solution

(a) Comparing Li and Be

Li (Lithium) and Be (Beryllium) are in the same period/row, with Li having an atomic number of 3 and Be having an atomic number of 4. Since metallic character decreases as we move from left to right across a period, Li will have a greater metallic character than Be.

(b) Comparing Li and Na

Li (Lithium) and Na (Sodium) belong to the same group/column of alkali metals. Li has an atomic number of 3, and Na has an atomic number of 11. Since metallic character increases as we move down a group, Na will have a greater metallic character than Li.

(c) Comparing Sn and P

Sn (Tin) and P (Phosphorus) are in different periods and groups. Sn is in the 14th group and 5th period, while P is in the 15th group and 3rd period. To compare their metallic character, consider their positions in the periodic table: Sn is to the left of P, and below it. As the metallic character increases down a group and decreases across a period from left to right, Sn will have a greater metallic character than P.

(d) Comparing Al and B

Al (Aluminum) and B (Boron) are in the same period/row, with Al having an atomic number of 13 and B having an atomic number of 5. Since metallic character decreases as we move from left to right across a period, Al will have a greater metallic character than B. In summary: (a) Li has a greater metallic character than Be. (b) Na has a greater metallic character than Li. (c) Sn has a greater metallic character than P. (d) Al has a greater metallic character than B.

Key concepts

Periodic Table Trends

Understanding the periodic table is crucial for predicting the properties of elements, including metallic character. One important trend is that metallic character decreases as you move from left to right across a period. This occurs because elements on the right side tend to gain electrons easily, which is a nonmetallic property. Conversely, metallic character increases as you move down a group, since the elements have more electron shells, making it easier for them to lose electrons and exhibit metallic properties. This explains why lithium (Li), being to the left in its period, is more metallic than beryllium (Be), and why sodium (Na), being lower in the same group, is more metallic than lithium.

Metallic Properties of Elements

Metallic elements are characterized by their ability to conduct heat and electricity, a shiny appearance (lustrous), and the capacity to be deformed without breaking (malleable and ductile). The metallic character of an element is also associated with its tendency to lose electrons to form positive ions (cations). Metals are typically found on the left side and center of the periodic table. Due to these inherent characteristics, tin (Sn), which falls to the left and further down the periodic table than phosphorus (P), will exhibit greater metallic properties.

Atomic Number Significance

The atomic number of an element is not just a sequential label; it signifies the number of protons in an atom's nucleus. This number defines the element and its position on the periodic table, thus influencing its chemical behavior. Since the number of valence electrons — which are important for bonding and chemical reactions — is determined by an element's position on the periodic table, the atomic number indirectly affects an element's metallic character. For instance, Aluminum (Al) with an atomic number of 13 has three valence electrons and is more metallic than boron (B) with an atomic number of 5, which has three valence electrons too but a lower electron shielding effect due to fewer inner electron shells.

Alkali Metals

Alkali metals make up the first group of the periodic table and are highly reactive with distinctive metallic properties like extreme softness, and high thermal and electrical conductivity. These elements have a single valence electron, which they tend to lose easily, making them highly reactive. For example, lithium (Li) belongs to the alkali metal group, and as we descend this group, we reach sodium (Na), which is more metallic. This trend amongst the alkali metals demonstrates an increase in reactivity and metallic character due in part to the increasing atomic radius and the related decrease in electronegativity as atomic number increases within this group.