Chemical bonds Flashcards
What is a chemical bond?
Interaction of an atom which binds them into molecules, ions, radicals and crystals. At the formation of chemical bonds, electrons can participate.
What are main characteristics of Chemical Bonds?
Chemical bond energy, length, valence angle, directionality of bonds
What is bond energy?
Minimum amount of energy required to break a bond. Denoted as E and is measured in kJ/mol or kcal/mol
The higher the bond enegy, the stronger the connection.
What does the value of the bond enegy depend on?
The nature of interacting atoms, type and order of bond..
What is chemical bond length?
The distance between the nuclei of the interacting atoms.
Denoted by the lettter “r” and is expressed in A (n.m)
What is bond angle?
Called the valence angle. The angle between H-O in H2O is 104.5, and the angle between bonds in CH4 is 109.5
What is bond multiplicity?
The number of electron pairs that bind 2 atoms.
Can be single, double, triple or quatinatery.
What does the increase in Bond multiplicity lead to?
Increase of bond energy, strength and decrease of length of bond.
How do atoms mainly form chemical bonds?
Through unpaired electrons. Main types of bonds are considered to be ionic, covalent, metallic and hydrogen bonds.
What is a covalent bond?
A chemical bond formed by a shared pair of electrons. Two electron and two center (holds two cores) connection.
All unpaired electrons and some paired are involved in formations of covalent bonds.
According to the method of overlapping electronic orbitals, how can bonds be distinguised?
They can be distinguished into Pi and Sigma bonds.
What are Sigma bonds?
Covalent bond where the atomic orbitals overlap along the line connecting the center of interacting atoms.
Always single bonds
What are Pi (π) bonds?
Covalent bond which, during formation, overlap above and below the connecting the center of interacting atoms.
However, they are only complimentary, double and triple bonds
What are the two types of covalent bonds?
Polar and Non-polar bonds
What is a non-polar bond?
Non-polar bonds is formed between two atoms with the same electromagnetivity, whre electron pairs equally belong to both atoms.
What is a Polar Bond?
A chemical bond formed by the atom which differ electromagnetivity but only slightly. Molecules of inorganic substances can serve as an example.
What is Donor-Acceptor?
Mechanism of covalent bond formation.
Chemical bond arise due to 2- electron cloud of one atom and the free orbital of another atom.
E.g When ammonium ion is formed, the 2-electron cloud of nitrogen and hydrogen atoms turn into aa molecular cloud, causing a fourth covalent bond known as the donor-accepting bond.
What are ionic bonds?
Type of bond formed by interaction of atoms whose electromagnetivity is very different.
What are ionic bonds based on?
They are based on electrostatic theory
What is the most stable electronic configuration?
This is when there are 8 electrons (oct) or 2 electrons (double) located at the external eletronic level
According to the electrostatic theory, how do ionic chemical bonds form?
Atoms, which lose or gain electrons, become ions (positive - cations). Due to this oppositely charged ions give rise to electrostatic attraction forces which keep them near each other and form the ionic bond.
What are ionic compound?
They are crystalline substances, which in solid state consist of regularly arranged postive and negative ions, while in aqueous state, they are ions rather than molecules
Which substances can form ionic bonds?
Alkali metals and halogens, alkalis and salts.
How do alkalis and salts dissociate in water?
NaOH = Na+ + OH-
Na2SO4 = 2Na+ + SO42-
Why is it difficult to set a sharp boundary between the types of chemical bonds?
This is due to chemical bonds being intermediate in many compounds. If the cemical bond is closer to ionic, then it is called an ion bond. If it is closer to a convalent bond, then it is called a covalent bond.
What are metallic bonds?
Bonds formed as a result of the interaction between metal ions and relatively free electrons. Characterizes all metals except liquid Mercury (Hg)
Physical properties of metals
High boiling point
High melting point
Metallic shine
Reflection from a metal surface of light rays
Good thermal conductivity
Good Electrical conductivity
Malliability
Ductlility
What is Hydrogen Bond?
The between a hydrogen atom of one molecule and a strongly electronegative atom of another molecule having a lone electon pair.
Why are hydrogen bonds indicated by dots?
This is to imply that it is much weaker than a covalent and ionic bonds but stronger than intermolecular interaction
Internal structure of particle arrangement in crystal lattices.
Crystalline or Amourphous state for solids
Random arrangement gas and liquid
How are particles ordered in crystal substances?
Particles are ordered, forming a spartial crystal lattice
What is the element mental cell?
This is the part of the crystal lattice whose parrallel translations in three dimensions allow you to build the entire crystal lattice
What are the types of crystal lattices and what do they depend on?
Ionic, Atomic, Molecular and Metallic. They depending on type of particles and nature of connection between them.
What are ionic crystal lattices?
These are crystal lattices with nose ions at the nodes.
Formed by substances with ionic bonds and their arrangement has the densest packing.
What are properties of ionic crystal lattice?
Strong bonds between ions.
High hardness.
Refractory
Low Voliatility
What are Atomic Crystal Lattices?
Crystal latices where atoms are located on the nodes
Interconnected by strong covalent bonds
What is a metallic crystal lattice?
This is when there is a neutral atom, positively charged ions and an electronym gas with free electrons at the nodes of the lattice
Electrostatic electrons attract cations, providing stability
What does the presence of electrons determine?
Good electrical and thermal conductivity, magnetic and other properties of metals
