Question

I have 5 questions that need help to answer 1) What are covalent bonds and how do they form ? 2) How do you know which elements and how many of each are in a compound ?

3) How can you find how many valence electrons an atom has ?
4) How many valence electrons do atoms need to be happy? Which elements are the exceptions?

Answer 1

Covalent bonds are formed by the sharing of electrons between atoms to achieve a full valence shell, typically following the octet rule. Nitrogen can form three covalent bonds, while chlorine usually forms one. Covalent compounds generally do not conduct electricity because they do not dissociate into ions.

Step-by-step explanation:

Understanding Covalent Bonds

Covalent bonds are formed when two atoms share electrons to achieve a more stable electron configuration. Atoms can form as many covalent bonds as they have unpaired electrons in their valence shell. The number of valence electrons an atom has can typically be found by its group number in the periodic table. For example, nitrogen, which is in group 5A, has five valence electrons and can form three covalent bonds by sharing three of its valence electrons with three hydrogen atoms. Chlorine, in group 7A, has seven valence electrons and typically forms one covalent bond.

To be 'happy' or chemically stable, atoms generally strive for a full valence shell, which is often eight electrons, known as the octet rule. This rule applies to many elements, but there are exceptions, such as hydrogen and helium, which are stable with two valence electrons. Additionally, elements in period 3 or higher can have expanded valence shells due to available d orbitals.

According to valence bond theory, electrons in covalent bonds are found in the overlapping orbitals of the bonded atoms, and for bonding to occur, the orbitals must overlap and electrons must have opposite spins. Lone pair electrons do not form covalent bonds but can influence the shape and polarity of molecules. Upon forming a covalent bond, elements like hydrogen will have a complete valence shell (2 electrons for hydrogen), while other non-hydrogen atoms aim for eight electrons in their valence shell as illustrated in their respective Lewis electron dot diagrams.

Group 6A elements, such as oxygen and sulfur, have six valence electrons and form two covalent bonds to satisfy the octet rule. The strength in covalent bonds arises from the shared electron interaction between atoms, and these bonds do not dissociate into ions; this is why molecular compounds with covalent bonds typically do not conduct electricity.

Answer 2

A covalent bond is one that is formed by two non-metal elements that, due to their low electronegativity difference, neither has the energy to steal the electrons from the other, so they share electrons with each other.

Covalent bonds form when the electronegativity difference between two elements is less than 1.7. In addition, the number of elements must be such that by sharing their electrons, all elements comply with the octet rule, that is, each element shares and completes 8 valence electrons.