<<–2/”>a >h2>Valency
Valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or Molecules.
The combining power, or affinity of an atom of a given element is determined by the number of hydrogen atoms that it combines with. In methane, carbon has a valence of 4; in ammonia, nitrogen has a valence of 3; in water, Oxygen has a valence of 2; and in hydrogen chloride, chlorine has a valence of 1. Chlorine, as it has a valence of one, can be substituted for hydrogen. Phosphorus has a valence of 5 in phosphorus pentachloride, PCl5. Valence diagrams of a compound represent the connectivity of the Elements, with lines drawn between two elements, sometimes called Bonds, representing a saturated valency for each element.
If the outermost shell has 8 electrons then the element is said to have a complete octet. By gaining, sharing and losing the electrons the atoms complete their outermost orbital and make an octet.
The capacity of an atom is described by the total number of electrons lost, gained or shared to complete its octet and it also determines the valency of the atom.
Chemical Bonding
The smallest particle of element is atom and the smallest particle in a compound is molecule. The force or the binding that keeps the atoms in the molecule combined during the formation of molecule is called chemical bonding. The concepts like that of Kossel-Lewis, VSEPR principle, valence bond theory, molecular orbital theory have been presented. In chemical bonding, it has more relation with orbitals around the nucleus and especially the valence orbitals.
Chemical bonds form if the resulting arrangement of the atoms has lower energy than the separated atoms i.e., atoms combine to attain a state of lower energy (potential) than that in the isolated ones, e.g. H2, P4, S8, H2O, C6H12O6 etc. Various changes in energy that occur when bonds form results from the movement of the valence electrons (the electrons in the outermost shell) of atoms.
Ionic bond
It involves the complete transfer of one or more electrons from one atom to another and is characterized by a large difference in electronegativity. An ionic bond is formed between an electropositive and an electronegative element.
Covalent bond
It involves the sharing of a pair of electrons between two atoms and is characterized by a small difference in electronegativity. A covalent bond is formed between two electronegative elements or could be generated between a less electropositive and an
electronegative element.
Metallic bond
It involves the free movement of valence electrons throughout the crystal and is also characterized by small difference in electronegativity. A metallic bond is formed between two electropositive elements,
Valency is the combining capacity of an atom. It is the number of electrons that an atom can lose, gain, or share in order to form a chemical bond. Valency is usually represented by a superscript number after the element symbol. For example, the valency of oxygen is 2, and the valency of hydrogen is 1.
Ionic bonding is a type of chemical bond that involves the transfer of electrons between atoms. In an ionic bond, one atom becomes positively charged by losing electrons, while the other atom becomes negatively charged by gaining electrons. The resulting ions are then attracted to each other by electrostatic forces.
Covalent bonding is a type of chemical bond that involves the sharing of electrons between atoms. In a covalent bond, the electrons are shared equally between the atoms. This type of bond is typically found in molecules that are made up of nonmetals.
Metallic bonding is a type of chemical bond that is found in metals. In metallic bonding, the atoms are held together by a sea of delocalized electrons. These electrons are free to move throughout the Metal, which is what gives metals their characteristic properties, such as conductivity and malleability.
Coordinate covalent bonding is a type of covalent bond in which one atom donates both electrons to the shared pair. This type of bond is often found in coordination complexes, where a central metal atom is surrounded by ligands.
Hydrogen bonding is a type of intermolecular force that is formed between a hydrogen atom that is covalently bonded to a highly electronegative atom, such as oxygen or nitrogen. The hydrogen atom is partially positively charged, while the electronegative atom is partially negatively charged. This results in a dipole-dipole attraction between the two atoms.
Van der Waals forces are weak intermolecular forces that are present in all molecules. These forces are due to the temporary distortion of the electron cloud around an atom, which results in a temporary dipole. This dipole can then induce a dipole in a neighboring atom, resulting in an attractive force.
Valency and chemical bonding are two important concepts in chemistry. Valency is the combining capacity of an atom, while chemical bonding is the force that holds atoms together. There are many different types of chemical bonds, including ionic bonding, covalent bonding, metallic bonding, coordinate covalent bonding, hydrogen bonding, and van der Waals forces. Each type of bond has its own unique properties and characteristics.
What is a chemical bond?
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, the electronegativity of atoms, and the Pauli exclusion principle.
What are the different types of chemical bonds?
There are four main types of chemical bonds: ionic bonds, covalent bonds, metallic bonds, and hydrogen bonds.
- Ionic bonds are formed when one atom donates an electron to another atom. The atom that donates the electron becomes a positively charged ion, while the atom that receives the electron becomes a negatively charged ion. The oppositely charged ions are attracted to each other, forming an ionic bond.
- Covalent bonds are formed when two atoms share electrons. The electrons are shared equally between the two atoms, and the atoms form a covalent bond.
- Metallic bonds are formed when atoms share electrons in a sea of electrons. The electrons are not bound to any particular atom, but are free to move throughout the metal.
- Hydrogen bonds are weak bonds that form between hydrogen atoms and electronegative atoms, such as oxygen or nitrogen. The hydrogen atom is attracted to the electronegative atom, forming a hydrogen bond.
What is the difference between a covalent bond and an ionic bond?
A covalent bond is a chemical bond that involves the sharing of electrons between atoms. An ionic bond is a chemical bond that involves the transfer of electrons from one atom to another.
In a covalent bond, the atoms share the electrons equally. This means that the electrons are not bound to any particular atom, but are shared between the two atoms. In an ionic bond, one atom donates an electron to the other atom. The atom that donates the electron becomes a positively charged ion, while the atom that receives the electron becomes a negatively charged ion. The oppositely charged ions are attracted to each other, forming an ionic bond.
What is the difference between a single bond, a double bond, and a triple bond?
A single bond is a covalent bond in which two atoms share one pair of electrons. A double bond is a covalent bond in which two atoms share two pairs of electrons. A triple bond is a covalent bond in which two atoms share three pairs of electrons.
Single bonds are the weakest type of covalent bond, while triple bonds are the strongest type of covalent bond. This is because triple bonds have more electrons shared between the two atoms than single bonds or double bonds.
What is the octet rule?
The octet rule is a chemical rule of thumb that states that atoms tend to form chemical bonds in order to have eight electrons in their valence shell. This is because atoms with eight electrons in their valence shell are more stable than atoms with fewer than eight electrons in their valence shell.
The octet rule is not always followed, but it is a useful guideline for understanding chemical bonding.
What is resonance?
Resonance is a phenomenon that occurs when two or more Lewis structures can be drawn for a molecule, and each structure contributes equally to the overall description of the molecule. The resonance structures are not separate entities, but rather they represent different ways of viewing the same molecule.
Resonance structures can be used to explain the bonding in molecules that have multiple possible Lewis structures. For example, the molecule ozone (O3) can be represented by the following two resonance structures:
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O=O=O
O^–O^+-O
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In the first resonance structure, the oxygen atoms are all equivalent. In the second resonance structure, the central oxygen atom is negatively charged, while the two outer oxygen atoms are positively charged. The actual structure of ozone is a hybrid of these two resonance structures.
What is hybridization?
Hybridization is a concept in chemistry that describes the mixing of atomic orbitals to form new orbitals with different shapes and energies. Hybridization is used to explain the bonding in molecules with multiple covalent bonds.
The most common type of hybridization is sp3 hybridization. In sp3 hybridization, one s orbital and three p orbitals mix to form four new sp3 orbitals. These sp3 orbitals are all directed towards the corners of a tetrahedron.
Other types of hybridization include sp2 hybridization, sp hybridization, and d-orbital hybridization.
What is molecular orbital theory?
Molecular orbital theory is a quantum mechanical model that describes the bonding in molecules. In molecular orbital theory, the electrons in a molecule are not localized around individual atoms, but rather they are delocalized throughout the entire molecule.
The molecular orbitals of a molecule are formed by the linear combination of the atomic orbitals of the atoms in the molecule. The molecular orbitals can be bonding, antibonding, or nonbonding.
Bonding molecular orbitals
Question 1
Which of the following is not a type of chemical bond?
(A) Ionic bond
(B) Covalent bond
(C) Metallic bond
(D) Hydrogen bond
(E) Van der Waals force
Answer
(E) Van der Waals force is not a type of chemical bond. It is a type of intermolecular force.
Question 2
In a covalent bond, atoms share electrons. Which of the following is not a factor that affects the strength of a covalent bond?
(A) The electronegativity of the atoms involved
(B) The number of electrons shared
(C) The distance between the atoms
(D) The type of orbitals involved
(E) The presence of lone pairs of electrons
Answer
(D) The type of orbitals involved does not affect the strength of a covalent bond. The other factors do affect the strength of a covalent bond.
Question 3
Which of the following is not a type of ionic bond?
(A) Sodium chloride (NaCl)
(B) Magnesium oxide (MgO)
(C) Calcium carbonate (CaCO3)
(D) Potassium bromide (KBr)
(E) Ammonium nitrate (NH4NO3)
Answer
(E) Ammonium nitrate (NH4NO3) is not a type of ionic bond. It is a type of covalent bond.
Question 4
Which of the following is not a type of metallic bond?
(A) Sodium
(B) Copper
(C) Gold
(D) Iron
(E) Magnesium
Answer
(E) Magnesium is not a type of metallic bond. It is a type of covalent bond.
Question 5
Which of the following is not a type of hydrogen bond?
(A) Water
(B) Ammonia
(C) Methanol
(D) Ethanol
(E) Hydrogen fluoride
Answer
(D) Ethanol is not a type of hydrogen bond. It is a type of covalent bond.
Question 6
Which of the following is not a type of van der Waals force?
(A) London dispersion force
(B) Dipole-dipole force
(C) Hydrogen bond
(D) Ion-dipole force
(E) Ion-induced dipole force
Answer
(C) Hydrogen bond is not a type of van der Waals force. It is a type of intermolecular force.
Question 7
Which of the following is not a factor that affects the strength of a van der Waals force?
(A) The polarizability of the atoms or molecules involved
(B) The surface area of the atoms or molecules involved
(C) The temperature of the atoms or molecules involved
(D) The distance between the atoms or molecules involved
(E) The type of atoms or molecules involved
Answer
(E) The type of atoms or molecules involved does not affect the strength of a van der Waals force. The other factors do affect the strength of a van der Waals force.