When elements in the same group form molecules, the number of outer-shell electrons involved is the same and so the number of bonds forming the molecule is the same roo.
Eg. Every element in group 2 (groupII) is a solid metal. When these elements bond with a non-metal, each forms an ion carrying a charge of +2. For this reason, they all form similar compounds with chlorine. Eg. MgCl2, CaCl2
Likewise, the elements of group 17 (group VII) form same number of bonds and therefore form similar molecules eg. HF, HCl
I dont understand the theory or the example please help me understand clearly
each element in group (column) 2, Be, Mg, Cs, Sr etc has just two electrons in its outermost shell. A full shell has more, like 8, and they are held tightly. If there are only two electrons in a shell that holds 8 when full, they are easily lured away by for example a Cl atom that is missing one electron to fill its outer shell. Each of two Cl atoms grabs one electron from the Mg for example and since the electrons are negative the two Cl atoms become -1 charge and the Mg becomes +2 because it now has two more + protons than - electrons. Since the Mg++ and the two Cl - are now of opposite charge and unlike charges attract, they are drawn to each other.
Thanks
You are welcome.
Sure, I'd be happy to help you understand!
In chemistry, elements are organized into groups on the periodic table based on their similar properties. The groups are numbered from 1 to 18, with elements in the same group having the same number of valence electrons. Valence electrons are the electrons in the outermost shell of an atom, and they play a crucial role in the formation of chemical bonds.
When elements in the same group form molecules, they tend to have similar properties because they have the same number of outer-shell electrons available for bonding. Let's take the examples you mentioned to better understand this concept.
Group 2, also known as Group II or the alkaline earth metals, includes elements like magnesium (Mg) and calcium (Ca). These elements have two valence electrons in their outermost shell. When they bond with a non-metal, such as chlorine (Cl), they tend to lose these two electrons and form a +2 charged ion. This is because metals tend to have a lower electron affinity, meaning they are more likely to lose electrons and form positive ions. So, both magnesium and calcium will form ions with a charge of +2.
When these +2 charged ions interact with chlorine, each chloride ion (Cl-) requires two electrons to achieve a stable electron configuration. Since the Group 2 elements have a +2 charge, each of them can provide two electrons to bond with two chloride ions. Therefore, compounds like magnesium chloride (MgCl2) and calcium chloride (CaCl2) are formed, where the metal is bonded to two chlorine atoms.
Similarly, Group 17, also known as Group VII or the halogens, includes elements like fluorine (F) and chlorine (Cl). These elements have seven valence electrons in their outermost shell. When they bond with a different element, such as hydrogen (H), they tend to gain one electron to complete their octet and achieve a stable electron configuration. So, fluorine will form an ion with a charge of -1, and chlorine will form an ion with a charge of -1.
When these -1 charged ions interact with hydrogen, each hydrogen atom can provide one electron to bond with one halogen ion. Therefore, compounds like hydrogen fluoride (HF) and hydrogen chloride (HCl) are formed, where the hydrogen atom is bonded to one halogen atom.
Overall, the similarity in properties and the formation of similar compounds among elements in the same group is due to their having the same number of outer-shell electrons available for bonding. Understanding the number of valence electrons and the tendencies of elements to gain, lose, or share electrons is key to understanding the formation of compounds and predicting their properties.
I hope this explanation helps you understand the theory and the examples more clearly! Let me know if you have any further questions.