Question

In Section 11.2 , it is said that iron and nickel represent maxinuin stability. Chemistry emphaxizes that helium is the most stable element? How can these claims be reconciled?

Short answer

The reconciliation of the claims lies in the understanding that they refer to two distinct types of stability – nuclear and chemical. Iron and nickel are the most stable in terms of nuclear physics because of their high binding energy per nucleon, while helium is the most stable in chemistry due to its full electron shell configuration.

Step-by-step solution

Understand Nuclear and Chemical Stability

To answer this question, it is important to understand the differences between nuclear and chemical stability. Nuclear stability refers to the stability of an element's nucleus and it is best understood by looking at the binding energy per nucleon. In this context, iron (Fe) and nickel (Ni) show maximum stability because they have the highest binding energy per nucleon. This physical phenomenon relates to nuclear reactions, such as fission or fusion.

Understanding Helium Stability

Helium, on the other hand, is considered to be the most stable element in a chemical context. This is because Helium has a completely full electron shell and is not prone to reactions. This is a chemical property, not related to the nucleus of the atom.

Reconciling the Two Concepts

So, these two statements can be reconciled by understanding they are referring to two different manifestations of stability: nuclear and chemical. Iron and nickel are the most stable in terms of nuclear forces and energy, while helium is the most chemically stable due to its electron configuration.

Key concepts

Binding Energy Per Nucleon

Understanding the concept of 'binding energy per nucleon' is crucial when discussing the stability of atomic nuclei. It represents the energy that would be required to remove a nucleon, which is either a proton or neutron, from the nucleus of an atom. A higher binding energy per nucleon indicates a more stable nucleus, as it means that more energy is required to break the nucleus apart.

In the context of iron (Fe) and nickel (Ni), these elements have among the highest binding energy per nucleon values. This is why, in nuclear terms, they are considered to exhibit maximum stability. The greater the binding energy per nucleon, the more work is necessary to separate the nucleons, hence such nuclei are less likely to undergo spontaneous changes, making them significantly stable.

Nuclear Stability

Nuclear stability is concerned with the dynamics and forces at play within an atomic nucleus. Several factors influence this stability, including the ratio of protons to neutrons and the overall size of the nucleus. Stable nuclei are less likely to change spontaneously through radioactive decay.

Iron and nickel have particularly stable ratios and the energies required to force these nuclei to change via nuclear reactions are incredibly high, demonstrating remarkable nuclear stability. The favorability of nuclear reactions such as fission and fusion is directly tied to the nuclear stability of the involved elements.

Chemical Stability

Unlike nuclear stability, which is concerned with the nucleus, chemical stability pertains to the likelihood of an atom to partake in chemical reactions and form compounds. This characteristic is highly dependent on the electron shell configuration. An atom like helium (He) is chemically inert and thus extraordinarily stable, as it has a full valence shell of electrons.

Atoms with a full outer electron shell, like He with its completed first shell, are chemically stable because they have little tendency to gain, lose, or share electrons. This is in stark contrast to elements with incomplete outer shells, which are more chemically reactive in pursuit of electron arrangements that confer stability.

Electron Shell Configuration

The electron shell configuration of an atom plays a pivotal role in determining its chemical reactivity and stability. Each shell can hold a certain number of electrons, and atoms strive for a full outer shell, a state known as a noble gas configuration. Helium's stability is derived from having a complete outer shell, which consists of two electrons.

Helium's electron configuration is denoted as 1s², indicating it has two electrons in its first and only energy level (shell). This complete shell means helium exhibits low reactivity and high chemical stability, as it does not need to engage in chemical bonding to achieve stability. Elements with incomplete outer shells, however, seek to fill or empty their outermost shells through bonding, making them more chemically reactive.