Arrange these elements in order of decreasing metallic character: Sr, N, Si, P, Ga, Al.

Understanding the periodic table is crucial for evaluating the metallic character of elements. Metallic character is one of the key attributes that varies predictably across the periodic table due to the table's arrangement based on atomic number and electron configuration.
As you move from left to right across a period, the metallic character generally decreases. This is because elements progressively gain more protons and electrons, leading to a stronger attraction between the positively charged nucleus and the negatively charged electrons. This makes the atoms less willing to lose electrons, a characteristic trait of metals.

Vertical Trends

Conversely, as you move down a group, the metallic character increases. This happens because additional electron shells are added, making the outermost electrons farther from the nucleus and therefore, more easily lost. The increased distance results in a weaker attraction between the nucleus and the electrons, which aligns with the tendency of metals to lose electrons and form cations.

• Moving across a period (left to right) decreases metallic character.
• Moving down a group (top to bottom) increases metallic character.

These trends help us determine that within the given elements, strontium (Sr), being furthest down and to the left, would exhibit the greatest metallic character.

Electron configuration plays a pivotal role in defining an element's chemical properties, including its metallic character. It refers to the distribution of electrons in an atom's orbitals. For metals, which have few valence electrons, these are loosely held and can be easily lost, leading to classic metallic properties like conductivity and malleability.

Energy Levels and Electron Shells

Elements with a smaller number of electron shells, and thus a valence electron closer to the nucleus, tend to hold on to their electrons more tightly and show less metallic character. As you advance down a group in the periodic table, additional shells are added, making it easier for electrons to be lost, enhancing the metallic character of the element.

• Elements with fewer electron shells generally have lower metallic character.
• Valence electrons in metals are often in higher-energy shells, more easily lost.

For instance, aluminum (Al) has its valence electrons in the third shell, while phosphorus (P) also has valence electrons in the third shell but with a stronger pull to the nucleus, indicating why Al has a higher metallic character than P.

The chemical properties of an element can be profoundly influenced by its metallic character. Metals tend to be good conductors of heat and electricity, are malleable, ductile, and often have a lustrous appearance. These properties are attributable to the ease with which metals can lose their valence electrons, allowing for free-flowing electrons which contribute to conductivity.

Reactivity and Compounds

Metals also typically participate in ionic bonding, as they tend to lose electrons and form positive ions (cations). Metallic character affects reactivity as well; more metallic elements are usually more reactive, especially with nonmetals. For example, the reactivity of alkali metals increases down the group.

• High metallic character leads to good conductivity and malleability.
• Metallic elements form cations easily and engage in ionic bonding.
• Reactivity with non-metals increases with metallic character.

In the list provided, strontium (Sr) will react more vigorously compared to silicon (Si), due to Sr's higher metallic character, and is indicative of the general reactivity trend among metals.