Question

Consider the elements $\mathrm{O},\mathrm{Ba},\mathrm{Co},\mathrm{Be},\mathrm{Br}$ , and Se. From this list, select the element that (a) is most electronegative, (b) exhibits a maximum oxidation state of $+7,(\mathrm{c})$ loses an electron most readily, (\mathbf{d} ) ~ f o r m s ~ $\pi$ bonds most readily, (e) is a transition metal, $(\mathbf{f})$ is a liquid at room temperature and pressure.

Short answer

(a) Most electronegative element: Oxygen (O) (b) Maximum oxidation state of +7: Bromine (Br) (c) Loses an electron most readily: Barium (Ba) (d) Forms π bonds most readily: Oxygen (O) (e) Is a transition metal: Cobalt (Co) (f) Is a liquid at room temperature and pressure: Bromine (Br)

Step-by-step solution

(a) Most electronegative element

To find the most electronegative element, we need to look at the periodic table and find the element with the highest electronegativity value. In the given list of elements, the electronegativity values are as follows: O: 3.44 Ba: 0.89 Co: 1.88 Be: 1.57 Br: 2.96 Se: 2.55 From these values, oxygen (O) has the highest electronegativity value, 3.44. Therefore, oxygen is the most electronegative element among the given elements.

(b) Maximum oxidation state of +7

To find the element that exhibits a maximum oxidation state of +7, we need to consider the elements' electron configurations and the number of valence electrons. Among the given elements, bromine (Br) is the one that can exhibit a maximum oxidation state of +7 due to its electron configuration [Ar] 3d10 4s2 4p5. In its maximum oxidation state, it loses all seven valence electrons to achieve a more stable electronic configuration.

(c) Loses an electron most readily

In order to determine which element loses an electron most readily, we should look for the element with the lowest ionization energy, as it represents the energy required to remove an electron from the atom. Among the given elements, the ionization energies are: O: 1314 kJ/mol Ba: 502.9 kJ/mol Co: 760 kJ/mol Be: 899 kJ/mol Br: 1139.9 kJ/mol Se: 941 kJ/mol From these values, barium (Ba) has the lowest ionization energy. Therefore, Ba loses an electron most readily among the given elements.

(d) Forms π bonds most readily

To determine which element forms π bonds most readily, we need to consider the elements' electron configurations and their ability to form double or triple bonds. Elements with unpaired electrons in the p orbitals are most likely to form π bonds. In the given list of elements, oxygen (O) has the electron configuration [He] 2s2 2p4, which has two unpaired electrons in the p orbital. Therefore, oxygen forms π bonds most readily.

(e) Is a transition metal

Transition metals are elements with partially filled d orbitals. Among the given elements, only cobalt (Co) is a transition metal with an electron configuration of [Ar] 3d7 4s2.

(f) Is a liquid at room temperature and pressure

To determine which element is a liquid at room temperature and pressure, we need to look at the physical state of each element at standard conditions. Among the given elements, bromine (Br) is a liquid at room temperature and pressure.

Key concepts

Electronegativity

Electronegativity is a chemical property that describes an atom's ability to attract and bind with electrons. It is crucial for understanding how atoms interact in molecules and can be found in the periodic table. The higher the electronegativity, the stronger the atom attracts electrons towards itself. Among the elements you provided, **oxygen (O)** is the most electronegative with a value of 3.44. This makes oxygen highly reactive, especially in forming bonds such as oxides. Electronegativity values decrease as you move down a group in the periodic table and increase as you move across a period from left to right.

This trend helps students predict which elements are likely to form ionic or covalent bonds. The concept of electronegativity also explains polar molecules. For example, in a water molecule (H2O), oxygen attracts the shared pair of electrons more strongly than hydrogen, resulting in a polar covalent bond.

Oxidation States

An oxidation state represents the degree of oxidation of an atom in a chemical compound; it's like bookkeeping for electrons in redox reactions. Bromine ( Br ) is the element from your list that exhibits a maximum oxidation state of +7 . This is observed in compounds like bromates (BrO₃-), where bromine is in its highest oxidation state. The oxidation states of elements are essential for predicting the outcomes of chemical reactions, particularly redox reactions.

Oxidation states vary across the periodic table and are determined by the number of valence electrons an atom can lose, gain, or share. In general, these states can be predicted based on an element's group number. However, transition metals can have multiple oxidation states because they have partially filled d orbitals that allow more flexibility in losing and gaining electrons.

Ionization Energy

Ionization energy is the energy needed to remove an electron from an atom in its gaseous state. This concept is vital because it helps us understand an element's reactivity. In the provided list, **barium (Ba)** is noted to lose an electron most readily due to its low ionization energy of 502.9 kJ/mol. Lower ionization energy indicates that an atom can easily shed electrons, turning into cations in compounds.

Ionization energy generally increases across a period from left to right due to an increase in effective nuclear charge. Conversely, it decreases down a group as the outer electrons are further from the nucleus and more shielded by inner electrons. Understanding ionization energy trends helps students predict atomic behavior in chemical environments, such as which elements are likely to form cations and participate in ionic bonding.

Transition Metals

Transition metals are unique due to their partially filled d orbitals, which provide these metals with specific properties such as high melting points, densities, and the ability to form colorful compounds. Among the elements listed, **cobalt (Co)** is the transition metal. Its electronic configuration [Ar] 3d⁷ 4s² gives it the typical characteristics of transition metals. These elements are known for their complex chemistry and ability to form various oxidation states, which is why they're frequently found as catalysts in industrial chemical reactions.

Transition metals tend to form compounds with vibrant colors due to d-d electron transitions under the absorption of visible light. They also tend to form stable complexes and alloys. These properties make transition metals integral to many technological and biological processes, enhancing their role in fields such as materials science and biochemistry.