Introduction
Oxygen is a colourless and odourless gas used in the respiration process by humans, which is converted into carbon dioxide.
One of the most important sulfur compounds is sulfuric acid, which is made with sulfur, hydrogen, and oxygen. Sulfuric acid has many commercial uses, including removing rust and adding pigment to paints and dyes. Furthermore, sulfuric acid is mixed with phosphate rock to produce phosphates for fertilizers, which helps provide plants with the necessary nutrients.
As a metalloid, selenium can conduct electricity and heat, especially when light is present. Therefore, selenium is used in solar cells, photocopiers, and cameras.
What are Chalcogens?
According to the current periodic table, chalcogens belong to group 16. Five distinct elements are classified as chalcogens: oxygen, sulphur, selenium, tellurium, and polonium. The synthetic element livermorium, abbreviated Lv, is thought to be a member of the chalcogen group. However, when it comes to the chalcogen family, it happens frequently that oxygen is left out. The features of the oxygen family are very distinct from those of the other elements in the groupings.
Physical Properties of Chalcogens
Atomic Radii of the Chalcogens
As an element moves down a group, its atomic radius, also known as its ionic radius, grows. In contrast to polonium, which has the biggest atomic radius, oxygen is the chalcogen with the smallest atomic radius.
Due to the addition of protons and the rising effective nuclear charge, the atomic radii of elements tend to decrease over time. As a result, as compared to lithium, oxygen has a substantially smaller atomic radius.
Ionization Enthalpies of Chalcogens
As the radius or size of the atom rises, the ionisation enthalpy drops. As a result, as one moves down in the group, the ionisation enthalpies of the chalcogens tend to drop. It is well known that oxygen has the highest ionisation enthalpy of all the chalcogen elements.
Since the effective nuclear charge rises as we move through the group and over the period, the ionisation enthalpy also tends to rise. So, compared to lithium, oxygen has a larger ionisation enthalpy.
Electron Gain Enthalpy of Group 16
The electron gain enthalpy tends to decrease as the atom's size grows. As a result, as one moves down the group, the electron gain enthalpies of chalcogens tend to drop. The compressed atomic structure of oxygen, which tends to support the interelectronic repulsion between the valence electrons and other approaching electrons, explains why oxygen has a lower negative electron gain enthalpy than sulphur. The correct order of electron gain enthalpy of chalcogens is S > Se > Te > O.
Electronegativities of Chalcogens
Due to several variables, including a rise in electron-electron repulsion and an increase in atomic radius, the electronegativity tends to decline as one moves down the group. Oxygen is the most electronegative chalcogen element when livermorium is excluded, whereas polonium is the least electronegative.
Metallic Nature of the Group 16 Elements
1. Sulfur and oxygen are non-metals.
2. Metalloids include selenium and tellurium.
3. Under normal circumstances, polonium typically displays metallic properties. But polonium is a radioactive substance.
Chemical Properties of the Chalcogens
Allotropy Exhibited by Group 16 Elements
The majority of chalcogens have many allotropes. Dioxygen and ozone are the two most typical oxygen allotropes. There are nine recognised allotropes of oxygen. Additionally, there are more than 20 known allotropes of sulphur.
There are two allotropes of polonium and at least five different allotropes of selenium. Monoclinic sulphur and rhombic sulphur are the two most stable allotropes of sulphur. Tellurium and selenium frequently occur in crystalline and amorphous forms.
Reactions Between Group 16 Elements and Hydrogen
When chalcogens interact with dihydrogen, they frequently produce hydrides, which have the general formula $${H}_{2}{M}$$, where $${{M}}$$ stands for any one of the chalcogen elements. The chemical reaction has the following general format:
$${M} (chalcogen) + {H}_{2} (dihydrogen) \to {H}_{2}{M} (hydride of chalcogen)$$
What Is Electron Gain Enthalpy?
The energy released when an electron is added to a single gaseous atom is known as the electron gain enthalpy. Energy can either be released or absorbed when an electron is added. It is frequently written as ΔH eg and is measured in electron volts per atom or kilojoules per mole. Electron gain enthalpy of group 16 elements should be in the following order: S>Se>Te>O.
Interesting Facts
Sulfur has been known since ancient times and has been mentioned in the Bible fifteen times. It was known to the ancient Greeks and commonly mined by the ancient Romans. It was also historically used as a component of Greek fire.
Early attempts to separate oxygen from the air were hampered by the fact that air was thought of as a single element up to the 17 and 18 centuries. Robert Hooke, Mikhail Lomonosov, Ole Borch, and Pierre Bayden successfully created oxygen but did not realise it at the time.
Tellurium was first discovered in 1783 by Franz Joseph Muller von Reichenstein.
Selenium was discovered in 1817 by Jöns Jacob Berzelius. Berzelius noticed a reddish-brown sediment at a sulfuric acid manufacturing plant. The sample was thought to contain arsenic. Berzelius initially thought that the sediment contained tellurium but came to realise that it also contained a new element, which he named selenium after the Greek moon goddess Selene.
Important Questions
1. Why do elements in the 15 and 16 groups have lower electron gain enthalpies than one another?
When an element's outer shell is half or filled with electrons, it achieves stability and requires energy to add more electrons. Group 15 elements have a different electronic arrangement of ns2 np3, which receives more stability than group 16 elements because it is half-filled. Since energy is needed to add an electron to group 15 elements, group 15 exhibits a positive electron gain enthalpy value. Therefore, the atoms in group 15 have a higher electron gain enthalpy than the elements in group 16.
2. What do the terms positive and negative electron gain enthalpy mean?
An atom's electron gain enthalpy is said to be positive if it spontaneously tends to gain electrons. In contrast, it is said to be negative if the atom is pushed to take an electron despite having a negative tendency to do so. The electron gain enthalpy generally decreases as the atomic number increases over time. As we move from left to right throughout a period, the atomic size reduces and the effective nuclear charge increases. As a result, adding an electron to a smaller atom will be simpler since the additional electron would typically be closer to the positively charged nucleus.
Conclusion
Moving down the group, the electron gain enthalpy becomes less negative. Going from left to right over some time makes it more detrimental. The electron gain enthalpy changed similarly for chalcogens, becoming less negative from top to bottom. Because it has 16 electrons, sulphur is more stable than the other elements in the group and has a lower negative tendency to gain electrons.
Multiple Choice Questions
1. When the atomic radius increases, electron gain enthalpy
(a) Increase
(b) Decrease
(c ) No change
(d) None of the above
Answer: (b) When the atomic radius increases, electron gain enthalpy decreases.
2. Which group of compounds have the largest electron gain enthalpy?
(a) Alkali metals
(b) Alkaline earth metals
(c ) Halogen family
(d) None of the above
Answer: (c ) Halogen family compounds have the largest electron gain enthalpy.
FAQs on Electron Gain Enthalpy of Chalcogens: Definition, Physical and Chemical Properties
1. What Sets Electron Affinity Apart from Electron Gain Enthalpy?
When a neutral atom or molecule (in the gaseous phase) accepts an electron from the outside, energy is produced. This is known as electron affinity. A neutral atom or molecule gaining an electron from the outside is known as an electron gain, which results in a change in enthalpy. The energy that is released when an isolated neutral atom picks up an extra electron is the main distinction between electron affinity and electron gain enthalpy. Electron affinity refers to an atom's propensity to pick up an electron.
2. Which group elements exhibit positive electron gain enthalpy?
The energy needed to introduce an electron into an atom is known as positive electron gain enthalpy. It is thought that an element is in its most stable form when its orbital is either half-full or totally filled. Therefore, adding an electron to a particular atom requires more energy. The element will have positive electron gain enthalpy in these situations. Due to their fully filled orbitals, all Nobel gases have positive electron gain enthalpies. Hence Nobel gases always consist of positive Electron Gain Enthalpy.
3. Do high positive electron gain enthalpy and less negative electron gain enthalpy mean the same?
Electron gain enthalpy is the amount of energy released when an isolated gaseous atom accepts an electron to become a monovalent gaseous anion. So if an atom has a tendency to gain an electron then its electron gain enthalpy is said to be negative, and if the atom is reluctant to gain an electron or we can say forced to accept it, its electron gain enthalpy is said to be positive. So high positive electron gain enthalpy means comparison among other atoms which possess positive electron gain enthalpy.....and less negative electron gain enthalpy is comparison among atoms possessing negative electron gain enthalpy.
