XI: Chemical bonding Flashcards
Who gave the octet rule?
Kossel and Lewis
Which bond is also known as electrovalent bond?
Ionic bond
Is ionic bond directional?
No
Is formation of gaseous cation by ionisation of gaseous atom endothermic or exothermic?
Endothermic
First electron gain enthalpy for a gaseous atom is _____ (endothermic/exothermic)?
Exothermic
Second electron gain enthalpy for a gaseous atom is _____ (endothermic/exothermic)?
Endothermic
How does size of the ions in a lattice affect lattice enthalpy?
Smaller the size of ions, lesser is the internuclear distance and greater will be the interionic attraction.
In sodium chloride lattice each sodium is surrounded by
six chlorine atom
In sodium chloride lattice each chlorine is surrounded by
Six sodium atoms
How many sodium and chlorine atoms are present in the unit cell of sodium chloride?
14 chlorine, 13 sodium
WHich positions does chlorine occupy in sodium chloride unit cell?
In a unit cell Cl- ions occupy all the centres of six faces and eight corners, where as one sodium ion is present at the centre of body and twelve sodium ions are present at all the twelve edges.
What type of interactions(forces) are present between ionic compounds and solvents like water?
Ionic dipole interactions
The unshared electrons in chlorine molecules are all the electrons that do not participate in covalent bond formation. True/false.
False. The unshared electrons are lone pairs (only the valence electrons).
What is covalency?
The number of electrons an element contributes for sharing while forming covalent bond.
Do ionic compounds exist as individual molecules?
No. They exist in a lattice as individual ions.
Do covalent compounds exist as individual molecules?
Yes
WHich is slower- ionic reaction or molecular reaction?
Molecular reaction
In a coordinate bond the donor atom may not have a complete octet. True/false?
False. Donor atom has a complete octet.
Can a coordinate bond once formed be distinguished from a covalent bond?
No
How is formal charge on a molecule calculated?
V − (1/2)S − L
V: valence electrons of atom
S: Number of shared electrons
L: Lone pairs
Are covalent bonds directional?
Yes
Which electron cloud occupies more space- lone pair or bond pair electron cloud?
Lone pair electron cloud
When is a compound said to have regular geometry in accordance with VSEPR theory?
When all the electron pairs around central atom are bond pairs.
When is a compound said to have distorted geometry in accordance with VSEPR theory?
When lone pairs are present on central atom in addition to bond pairs.
Among molecules having irregular but similar geometry, how does bond angle vary with electronegativity of central atom?
Bond angle decreases with decreasing electronegativity of central atom.
Among molecules having irregular but similar geometry, how does bond angle vary when central atom is kept same but electronegativity of surrounding atoms decreases?
Bond angle increases
Does bond angle vary among molecules having regular but similar geometry with varying electronegativity of central or surrounding atoms?
No
Is sigma bond formed by overlap of s and s orbitals stronger or sigma bond formed by overlap of p-p orbitals?
sigma bond formed by overlap of p-p orbitals
Which bond determines the shape of molecule- sigma or pi?
Sigma bond
In resonance structures, like charges can reside on adjacent atoms. True/false
False.
A resonance hybrid can be represented by a Lewis structure. True/false?
False.
What is the formula for bond order in resonance forms?
Total number of bonds between
two atoms in all resonating forms
___________________________
Total number of resonating forms
An atomic orbital is polycentric and a molecular orbital is monocentric. True/false?
False.
An atomic orbital is monocentric and a molecular orbital is polycentric.
Which is more pronounced according to molecular orbital theory- destabilising effect of antibonding orbitals or stabilising effect of bonding orbitals?
destabilising effect of antibonding orbitals
Which type of molecular orbitals are called sigma orbitals?
Those which are cylindrically symmetrical about the intermolecular axis.
If the number of electrons in bonding orbitals is equal to the number of electrons in antibonding orbitals, is the molecule stable?
No
What type of interactions are hydrogen bonds?
Dipole dipole interaction
Which has a smaller SiO bond order H2SiO or Cl2SiO?
Cl2SiO
due to back bonding
Does methane have a net dipole moment?
Dipole moment of methane is zero
