Question

Sport Bottles Some sports bottles are made of Lexan, a plastic containing a compound of the elements chlorine, carbon, and oxygen. Order these elements from greatest to least according to atomic radius and ionic radius.

Short answer

The order of the elements chlorine, carbon, and oxygen from greatest to least according to atomic radius and ionic radius is: Carbon > Oxygen > Chlorine. This is based on the trends observed in the periodic table, as atomic radius generally decreases from left to right across a period, while ionic radius increases with the addition of more electrons.

Step-by-step solution

Refer to the periodic table

Identify the positions of the elements chlorine, carbon, and oxygen in the periodic table. Remember that the atomic number of carbon is 6, oxygen is 8, and chlorine is 17.

Examine the trends in atomic radius

Moving from left to right across a period, the atomic radius generally decreases due to the increasing effective nuclear charge experienced by electrons. Moving down a group, the atomic radius increases due to the increase in electron shells. Since chlorine, carbon, and oxygen belong to the same period (Period 2), we observe that atomic radius decreases from left to right, so the order is: Carbon > Oxygen > Chlorine

Examine the trends in ionic radius

When an atom gains or loses electrons to form an ion, its ionic radius changes. For the elements in question, carbon forms a \(C^{4-}\) ion, oxygen forms an \(O^{2-}\) ion, and chlorine forms a \(Cl^{-}\) ion. As the number of electrons added to an atom increases, the size of the ion increases due to additional electron-electron repulsion and a decrease in effective nuclear charge experienced by the outermost electrons. Hence, the order of ionic radius is: Carbon > Oxygen > Chlorine

Provide the final answer

The order of the elements from greatest to least according to atomic radius and ionic radius is: Carbon > Oxygen > Chlorine

Key concepts

Understanding Periodic Table Trends

The periodic table is not just a tabular arrangement of elements, but also a map illustrating various trends among the properties of elements. A key trend we observe is regarding atomic radius—which is essentially the distance from the center of the nucleus of an atom to its outermost electron shell.

As we move across a period from left to right, the atomic radius tends to decrease. This occurs because each successive element in a period contains more protons than the previous one, leading to a stronger effective nuclear charge that pulls the electron cloud closer to the nucleus. Conversely, when we move down a group, the atomic radius increases. This is because there are more electron shells surrounding the nucleus, each shell being farther from the nucleus than the one before.

Defining Atomic Radius

Atomic radius is a term used to describe the size of an atom. It can be somewhat tricky to define, as it's largely based on the area in which the probability of finding an electron is highest. However, for simplicity, we can think of the atomic radius as the distance from an atom’s nucleus to the outer boundary of its electron cloud.

This distance is not fixed; it can change based on the atom's position in the periodic table and the type of bond it's involved in. Generally, the atomic radius is larger for atoms with more electron shells, and it becomes smaller with an increase in effective nuclear charge, which pulls electrons tighter to the nucleus.

Ionic Radius: An Ion's Size

The ionic radius is the measure of an atom’s ion once it has gained or lost electrons. Anions, which are negatively charged ions, often see an increase in size compared to their neutral atoms because the addition of electrons increases electron-electron repulsion and reduces the effective nuclear charge.

Cations, on the other hand, are positively charged ions and are smaller than their neutral atoms due to the loss of electron shells or reduced electron-electron repulsion. This size change has profound effects on the physical and chemical properties of the ions, playing a critical role in their behavior, such as in the formation of salts.

Electron Shells and Their Significance

Electron shells are layers that surround an atom's nucleus, where electrons are most likely to be found. The number of electron shells an atom has directly impacts its atomic radius—the more shells, the larger the radius.

Each shell can hold only a certain number of electrons, and they fill from the innermost shell outward. When an atom has more electron shells, there’s a greater distance between the outer electrons and the nucleus, causing the atom to be larger overall. These shells not only determine the size of the atom but also influence how an atom will interact or bond with others.

The Role of Effective Nuclear Charge

Effective nuclear charge (ENC) refers to the net positive charge experienced by electrons in the valence shell of an atom. While the actual nuclear charge is based on the number of protons in an atom's nucleus, the ENC takes into account the shielding effect of electrons in inner shells.

This concept is vital because it helps explain why atoms across a period become smaller despite an increasing number of electrons. Higher ENC leads to a stronger attraction between the nucleus and the valence electrons, thus pulling them closer and decreasing the atomic radius. Understanding ENC is crucial for grasping trends in the periodic table and predicting the chemical behavior of elements.