Question

For each of the questions, four choices have been provided. Select the correct alternative. An element \(\mathrm{X}\) has low ionization energy and another element \(\mathrm{Y}\) has high electron affinity. The bond formed between them could be (a) ionic (b) polar covalent (c) coordinate covalent (d) non-polar covalent

Short answer

Answer: (a) Ionic

Step-by-step solution

Understanding terms involved

Ionization energy is the energy required to remove an electron from an atom. A low ionization energy means that it is relatively easy to remove an electron from element X. Electron affinity is the energy released when an atom gains an electron. High electron affinity means that element Y readily accepts electrons.

Predicting bond formation

When an element with low ionization energy combines with an element having high electron affinity, one can transfer an electron from the first element to the second, forming ions. The resulting positively charged ion (cation) and negatively charged ion (anion) will attract each other, leading to the formation of an ionic bond.

Answer

Given the properties of the two elements, the most likely bond type formed between them is ionic. Thus, the correct answer is (a) ionic.

Key concepts

Ionization Energy

Ionization energy refers to the amount of energy that is needed to remove an electron from an atom. If an element has low ionization energy, it means that its electrons are loosely held and can be removed with relative ease. Imagine it's like plucking a ripe fruit from a tree. Elements on the left side of the periodic table, like alkali metals, often have low ionization energies, which makes them particularly good at losing electrons and forming positive ions, also known as cations. This property is crucial in chemical reactions, especially in forming ionic bonds.

Electron Affinity

Electron affinity is the energy change that occurs when an atom gains an electron. A large, positive electron affinity value indicates that an atom attracts electrons strongly, which is typical of nonmetals like halogens. When an atom has high electron affinity, it readily accepts an additional electron, becoming a negatively charged ion, known as an anion. This attraction for electrons plays a vital role in the formation of chemical bonds, particularly ionic ones, as it can lead to the capture of electrons from elements with low ionization energy.

Chemical Bonding

Chemical bonding is the process by which atoms combine to form compounds. Atoms bond because they seek stability, which typically means having a full outer electron shell.

• Ionic Bonds: Formed when electrons are transferred from one atom to another, creating charged ions that are held together by electrostatic forces. Useful for compounds like salts.
• Covalent Bonds: Involve sharing of electrons between atoms. They are common in organic compounds.
• Polar Covalent Bonds: A type of covalent bond where electrons are shared unequally, causing slight charges.
• Non-polar Covalent Bonds: Where the electrons are shared equally among atoms.

The interplay between ionization energy and electron affinity is a driving factor in determining the type of chemical bond that will form between atoms.

Cations and Anions

Cations and anions are types of ions, which are charged particles.

• Cations: These are positively charged ions, formed when an atom loses one or more electrons. Metals, with their low ionization energies, are typical cation formers.
• Anions: These are negatively charged ions, created when an atom gains electrons. Nonmetals, which often have high electron affinities, tend to become anions.

When cations and anions come together, they form ionic compounds. The force of attraction between the opposite charges is what holds these compounds together, leading to the formation of a stable substance. This interaction is fundamental to the creation of many everyday substances like table salt.