2.1.4 [Electronegativity and bond polarity] Flashcards
What is electronegativity?
Electronegativity is the ability of an atom to attract a bonding pair of electrons
Electronegativity:
Decreases down a group of the periodic table
Increases from left to right across a period
The greater the electronegativity of an atom the more it attracts electrons towards it.
What is the distribution of electron density like in a compound containing 2 atoms of the same element?
2 atoms of the same element bonded together by overlap of atomic orbitals. The distribution of electron density between 2 nuclei will be symmetrical this is because the ability of each atom to attract the bonding pair of electrons is identical.
What is polar covalent bond ?
A type of covalent bond between 2 atoms where the bonding electrons are unequally distributed because of this one atom carriers a slight negative charge and other slight positive
What is electron density like with a compound of 2 atoms of a different atoms covalently bonded together (Polar covalent bond)?
If the 2 atoms bonded together are from elements that have different electronegativities then the distribution of electron density will not be symmetrical about the 2 nuclei.
Density closely spaced to the more electronegative atom.
How does polar covalent bonds work in HCl compound?
Since electron density is higher around the chlorine atom that end of the molecule has acquired a slightly negative charge. represented by sigma + symbol. The other end of the molecule has acquired a slightly positive charge represented by sigma - charge.
Bond like this is called a polar covalent bond. A way to show this is an arrow in the direction of the electron drift. Electron pulled towards chlorine.
What are the factors affecting electronegativity?
Nuclear charge
Distance from the nucleus
Electron shielding
What is a polar bond?
Polar bonds result from a large difference in electronegativity between 2 atoms forming a covalent bond. Tables of electronegativity can be used to determine if it is polar or not. If difference in electronegativity between 2 atoms was between 0.4 and 1.7 bond is polar covalent. If it is greater than this bond is ionic.
Elements that are close together on the periodic table will not form polar bonds.
What is the continuum of bonding types?
Polar covalent bonds can be thought of as being 2 ideals on bonding types. These ideals are:
Pure (100%) covalent
Pure (100%) ionic
Polar covalent bond has a degree of ionic character.
Why does electronegativity increase across a period
Electronegativity increases along a period as atomic radius decreases. Nuclear charge increases number of shielding electrons remains constant so attraction to shared electron paired increases.
Why does electronegativity decreases down a group?
As go down the group the nuclear charge increases, there is an increase in the number of shielding electrons and the shared electron pair is further from the nucleus so is attracted less strongly.
How are Non polar covalent bonds, Polar covalent bonds and Ionic bonds formed?
Non polar covalent bonds: No difference between electronegativity
Polar covalent bond: Small difference in electronegativity
Ionic bonding: Large difference in electronegativity
