Chemical Bonding Flashcards
(22 cards)
What is an electrovalent bond
Bond between two atoms held by electrostatic force due to complete transfer of electron
How to calculate the heat of formation
sublimation energy + dissociation energy/2 + ionization enthalpy - electron affinity - lattice energy
What is lattice energy
The energy released when one mole of a crystalline solid is formed when oppositely charged particles gets packed closely
What are the factors of lattice energy
size of the ion, charge of the ion
What is an ionic crystal
A three dimensional aggregate formed when oppositely charged ions are arranged in a regular continuous geometrical pattern
What are the reasons for variable valency
- Unstable electronic configuration
- Inert pair effect
Explain the role of unstable electronic configuration in variable valency
Transition metals need to lose many electrons to attain octet. After losing a few though, due to an increase in nuclear charge, more electrons are not lost
Explain the role of inert pair effect in variable valency
S-electrons penetrate closer to the nucleus, hence they require more energy to be removed. this causes variable valency
How does inert pair effect vary down a group
It increases. In a covalent bond down a group, the bond strength decreases due to the large distance between the atoms. The energy due to the bond isn’t enough to excite the s-electrons so they do not take part
What is covalent bond
A bond formed by the mutual sharing of electrons between two atoms
What are isomorphs
the are crystalline compounds with similar arrangements of atoms and geometry
What are the exceptions to the octet rule
- Hydrogen and Helium
- Couldn’t explain electron deficient like BeCl2, BF3
- Could not explain PF5, IF7, which have more than 8 e
- Failed to explain why inert gases form compound
- Odd electron bonds
Explain why the octet rule failed
- Sidgwick’s max covalence rule - the max covalency of an element is limited according to the period
- Sugden’s view of singlet linkage - an element having octet could share one electron
- Atoms can use vacant d orbital to expand their octet
What is sigma bond
A bond formed by head-on overlapping of orbitals along the internuclear axis
Strong, symmetrical, free rotation
What is pi bond
Bond formed by sideways overlapping of p orbitals, perpendicular to internuclear axis
Why do bond pairs have the least repulsion
Since the are under the influence of two nuclei, the contract and occupy a smaller space resulting in less repulsion
State the geometry and angle of VSEPR
- 2 pair - linear - 180
- 3 pair - trigonal planar - 120
- 4 pair - tetrahedral - 109.5
- 5 pair - trigonal bipyramid - 120, 90
- 6 pair - octahedral - 90
What is the bond angle of distorted pyramid
107
What is the bond angle of bent or v shape
104.5
What is hybridization
It is the intermixing of orbitals having similar energy to form orbitals with exactly the same energy with identical shapes and symmetrical orientations in space
What is sigma molecular orbital
It the the molecular orbital formed from the head-on overlapping of s-s atomic orbitals or p-p atomic orbitals or s-p
What is pi molecular orbital
A molecular orbital formed from sideways or lateral overlap of two p orbitals
