Chemical Bond Flashcards
What e- take part in chemical bonds
Valence e-
What are chemical bonds
Chemical bonds=interactions that account for the association of atoms into molecules, ions and crystals
Why do atoms form chemical bonds
To achive more stable electronic confoguration
What impact do chemical bonds have on the energy of the system
They minimize the total energy of the system
What does miminun of the potential energy curve corresponds to
Bond formation. The deeper the curve is=stronger the bond
What is the bond energy
Measure of bond strength of a chem.bond. it is the amount of energy needed to break the atoms involved in chem.bond into free atoms
What is bond length
It is defined as the mean distance between the centers of 2 atoms in a molecule. The smaller the distance=more stable the bond
What is bond angle
Angle between 2 bonds, usually measured in degrees
What is bond angle related to
Dimension and electronegativity of the atoms forming a bond
How can e- behave in a bond
- It can be shared=>non electrostatic bond; covalent bond
- It can be transfered from one atom to another=>electrostatic bond; ionic bond
Explain polarity of covalent bonds
If the atoms have same electronegaticity is is non polar covalent bond.(H-H)
If they have different electronegativity e- isn’t located exactly on the middle but closer to the nucleus of more electronegatice atom which forms dipoles. That is polar covalent bond
What is Lewis structure
Bidimensional representation of the structiral formula and it doesnt give information abt 3D structure
Explain how is Lewis structure written
Dots are used for valence e-.Lines are drawn for bonds. Lond pairs are drawn as pair of dots
Characteristic of ionic compounds
-solid crystals
-high melting temperature
-the melted compound conducts electrcity
-they can dissolve in water and comduct electricity
Explain formation of crystalline solid
There is forces of attraction between opposite charges and repulsion between similiar charges and that orients an ion in such way where positive ion is surrounded by negative ions and vice versa. They are arranged in such manner that positive and negative charges alternate and balance each other, overall charge of the substance being zero
What is lattice energy
Energy change upon formation of a crystalline ionic compound from its constituent gaseous ions
What does binding in covalent bond arises from
Electrostatic attraction of both nuclei for the same electrons
Some characteristic of covalent bond
It is directional and it gived definitive shapes. It is very strong bond
What is coordinate covalent bond
When both e- come from the same atom
Ex. (H+) + (NH3)=(NH4+)
What is octet rule
Tendency of an atom in a molecule to have 8e- in the valence shell
What does it mean when some element is electron deficient and hypervalent
Electron deficient is when atom in a molecule doesnt have a full octet
And hypervalent is whem it has expanded octet
Why would some molecule be radical
When it has 1 unpaired e-(ex. NO-one e- in N is unpaired,N is e- deficient)
What is electronegativity difference in bonds
In non polar covalent /\X=0
In polar covalent /\X=0.9
In ionic /_\X =2.1
What is bond order
Number of bonds between 2 atoms
•Single bond=two atoms share 1 couple of e-(bond order of 1)
•Multiple bond= the atoms share 2 or more couple of e-
°Double bond-bond order 2
°Triple bond-bond order 3
What is isolated atom
Number of e- associated with the atom is the same ad number of valence e-
What is formal charge
Difference between the number of valence e- in a free atom and number of e- assigned to the atom in the Lewis structure
Formar charge= valence e- - number of bonds - number of unshared e-
How does determination of Lewis structure works
- Determine the total number of valence e- in the molecule. This will be sum of the valence e- of all atoms + charge
- Choose a central atom(the least electronegative one or the atom with the highest valence)
- Draw skeletal structure connecting the atoms with 1 bond
- Add the rest of the e- to the outside atoms. And the left over e- to the central atom
- Check if everyone has a full octet. If the central one doesnt have a full octet, a lone pair from a peripheral atom may be pushed to create double or triple bonds
- Determine formal charges and decide which structure is the most probable
What is prefered Lewis structure
-one with fewer number of formal charges
-with less formal charges
-charges should match electronegativity
What is resonance
It is used when no single Lewis structure accuratly represents the observing bonding in a molecule. The actual structure is represented by an avarage of several resonance forms
How are resonance forms showed
With double-headed arrow between them
Do resonance forms have independent existance
No. The real steicture is avarage of the resonance forms and there is not an equilibrium or osciallation between them
