1.5.2 Bond Polarity (Physical Chemistry) Flashcards
Electronegativity is
the power of an atom to attract the pair of electrons in a covalent bond towards itself
The electron distribution in a covalent bond between elements with different electronegativities will be
unsymmetrical
This phenomenon arises from
the positive nucleus’s ability to attract the negatively charged electrons, in the outer shells, towards itself
The Pauling scale is used to
assign a value of electronegativity for each atom
First three rows of the periodic table showing electronegativity values diagram
Fluorine is the
most electronegative atom on the Periodic Table, with a value of 4.0 on the Pauling Scale
Fluorine is best at
attracting electron density towards itself when covalently bonded to another atom
Electron distribution in the C-F bond of fluoromethane diagram
Attraction exists between
the positively charged protons in the nucleus and negatively charged electrons found in the energy levels of an atom
An increase in the number of protons leads to
an increase in nuclear attraction for the electrons in the outer shells
An increased nuclear charge results in
an increased electronegativity
The atomic radius is
the distance between the nucleus and electrons in the outermost shell
Electrons closer to the nucleus are
more strongly attracted towards its positive nucleus
Those electrons further away from the nucleus are
less strongly attracted towards the nucleus
Tn increased atomic radius results in
electronegativity decreases
Filled energy levels can
shield (mask) the effect of the nuclear charge causing the outer electrons to be less attracted to the nucleus
The addition of extra shells and subshells in an atom will
cause the outer electrons to experience less of the attractive force of the nucleus
Sodium (period 3, group 1) has higher electronegativity than caesium (period 6, group 1) as
it has fewer shells and therefore the outer electrons experience less shielding than in caesium
An increased number of inner shells and subshells will result in
a decreased electronegativity
Electronegativity varies across
periods and down the groups of the periodic table
Down a group
- There is a decrease in
electronegativity
Down a group
- The nuclear charge
increases as more protons are being added to the nucleus
Down a group
- Each element has an extra filled electron shell, which
increases shielding
Down a group
- The addition of the extra shells
increases the distance between the nucleus and the outer electrons resulting in larger atomic radii
Down a group
- Overall, there is
decrease in attraction between the nucleus and outer bonding electrons
Electronegativity decreases going down the groups of the periodic table diagram
Across a period
- Electronegativity
increases
Across a period
- The nuclear charge
increases with the addition of protons to the nucleus
Across a period
- Shielding remains
relatively constant across the period as no new shells are being added to the atoms
Across a period
- The nucleus has
an increasingly strong attraction for the bonding pair of electrons of atoms across the period of the periodic table
Across a period
- The nucleus has an increasingly strong attraction for the bonding pair of electrons of atoms across the period of the periodic table, this results in
smaller atomic radii
Electronegativity increases going across the periods of the Periodic Table diagram
