Question

Using the periodic table, identify each element given the description: (a) the most electronegative element of the alkaline earth metals (b) the noble gas with the highest first ionization energy (c) the element in Period 4 with the lowest first ionization energy (d) the element with the highest electronegativity (e) the alkali metal with the largest radius (f) the element in Period 2 with the smallest radius

Short answer

a) Beryllium (Be), b) Helium (He), c) Potassium (K), d) Fluorine (F), e) Francium (Fr), f) Neon (Ne)

Step-by-step solution

Identify the most electronegative element of the alkaline earth metals

The alkaline earth metals are located in group 2 of the periodic table. They include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). Electronegativity generally increases across a period, therefore the most electronegative alkaline earth metal is beryllium (Be).

Identify the noble gas with the highest first ionization energy

Noble gases are located in group 18 of the periodic table. Their first ionization energies decrease down the group due to increasing atomic size. Therefore, the noble gas with the highest first ionization energy is helium (He).

Identify the element in Period 4 with the lowest first ionization energy

Looking at Period 4 of the periodic table, the first ionization energy generally decreases from left to right. The transition metals have higher first ionization energies than the alkali and alkaline earth metals located at the beginning of the period. The element in Period 4 with the lowest first ionization energy is potassium (K).

Identify the element with the highest electronegativity

Electronegativity increases from left to right across a period and decreases down a group. The element with the highest electronegativity on the periodic table is fluorine (F).

Identify the alkali metal with the largest radius

Alkali metals are located in group 1 of the periodic table. Atomic radius increases down the group as the number of electron shells increases. Therefore, the alkali metal with the largest radius is francium (Fr).

Identify the element in Period 2 with the smallest radius

Period 2 of the periodic table includes the elements from lithium (Li) to neon (Ne). Atomic radius generally decreases moving from left to right across a period due to the increasing nuclear charge attracting the electrons more strongly. The element in Period 2 with the smallest radius is neon (Ne).

Key concepts

Electronegativity

Electronegativity is a measure of an atom's ability to attract and hold onto electrons when it is part of a compound. This property is essential for understanding the chemical behavior of elements. The most electronegative element is fluorine (F), which has a strong attraction for electrons. In general, electronegativity increases across a period from left to right due to a higher nuclear charge which pulls electrons closer. It decreases down a group as additional electron shells reduce the pull on valence electrons. Knowledge of electronegativity values is crucial in predicting the type of bond (ionic or covalent) and polarity of compounds.

For instance, in the exercise, beryllium (Be) was identified as the most electronegative alkaline earth metal based on its position in the periodic table. Electrons in a Be compound are more attracted to the beryllium atom compared to other alkaline earth metals.

First Ionization Energy

The first ionization energy is the energy required to remove the most loosely held electron from an atom in its gaseous state. An element with a high ionization energy holds onto its electrons tightly, which often correlates with nonmetallic properties. In the periodic table, the first ionization energy tends to increase across a period due to the increasing nuclear charge. Conversely, it decreases down a group as the outer electron becomes farther from the nucleus and more shielded by the inner electrons, making it easier to remove.

Helium (He), the noble gas identified in the exercise, has the highest first ionization energy among noble gases because of its small size and strong hold on its two electrons. Potassium (K), with the lowest first ionization energy in Period 4, can easily lose an electron, which is why it's highly reactive and classified as an alkali metal.

Atomic Radius

Atomic radius is the distance from the nucleus to the outermost stable electron orbit. It can impact an atom's volume, reactivity, and its ability to bond with other atoms. As we move down a group, the atomic radius increases because each successive element has an additional electron shell. Moving from left to right across a period, the atomic radius generally decreases. This happens because as protons are added to the nucleus, they draw the electrons closer, shrinking the size of the atom.

In the context of our exercise, neon (Ne) has the smallest atomic radius in Period 2, while francium (Fr) among the alkali metals has the largest radius due to its position at the bottom of its group.

Alkaline Earth Metals

The alkaline earth metals, found in group 2 of the periodic table, include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These elements are characterized by their shiny appearance and their ability to lose two electrons, forming +2 ions. They are less reactive than their neighbors, the alkali metals, but still react with water to form hydroxides.

Alkaline earth metals have relatively low electronegativity and ionization energies compared to other elements in the same period. Beryllium, the most electronegative among them, still forms covalent bonds more often than the other alkaline earth metals due to its small size and relatively high ionization energy.

Noble Gases

Noble gases, located in group 18 of the periodic table, are odorless, colorless, and almost completely nonreactive. The full valence shell of these elements makes them exceptionally stable and unlikely to gain or lose electrons, leading to their lack of chemical reactivity. The noble gases include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn).

Helium has the highest first ionization energy among them due to its small radius and tight hold on its electrons. Noble gases are frequently used in lighting, welding, and space applications due to their stability and non-reactivity.

Alkali Metals

Alkali metals, found in group 1 of the periodic table, are highly reactive elements characterized by their single valence electron which they readily lose to form +1 ions. These metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). As we move down the group, their reactivity increases, and their atomic radius grows larger due to the addition of electron shells.

Francium, though rarely encountered due to its radioactivity, has the largest atomic radius of the alkali metals. These metals are so reactive that they require special storage to prevent reactions with air or water.