3.4- ELECTRONEGATIVITY- BOND POLARITY IN COVALENT BONDS Flashcards
What are the forces that hold atoms together all about?
attraction of positive charges to negative charges
What happens in ionic bonding? (transfer)
complete transfer of electrons from one atom to another
Are the electrons always evenly spread out in a covalent bond?
no
When are the electrons not evenly spread out in a covalent bond?
when one of the atoms is better at attracting electrons than the other one
What is the atom that is better at attracting the electrons than the other atom in a covalent bond said to be?
more electronegative
What is the definition of electronegativity?
power of an atom to attract the electron density in a covalent bond towards itself
What is the term electron density often used to describe?
way the negative charge is distributed in a molecule
What is used as a measure of electronegativity?
Pauling scale
What does the Pauling scale run from?
0 to 4
What does a greater number on the Pauling scale mean?
more electronegative the atom
What number does the noble gases have on the Pauling scale?
no number
Why do the noble gases not have a number on the Pauling scale?
generally they do not form covalent bonds
What does electronegativity depend on? (3)
nuclear charge
distance between nucleus and outer shell electrons
shielding of nuclear charge by electrons in inner shells
What happens to electronegativity as the size of the atom decreases?
smaller the atom, greater the electronegativity
Why does electronegativity increase as the size of the atom is smaller?
closer the nucleus is to the shared outer main level electrons
What happens to electronegativity the larger the nuclear charge?
greater the electronegativity
How does electronegativity change going up a group?
increases
Why does electronegativity increase going up a group?
less shielding by electrons in inner shells
How does electronegativity change going across a period?
increases
Why does electronegativity increase going across a group? (3)
nuclear charge increases
number of inner main levels remain the same
atoms become smaller
Where are the more electronegative atoms found on the periodic table?
top right-hand corner (ignoring noble gases)
What are the most electronegative atoms? (4)
fluorine
oxygen
nitrogen
chlorine
What is polarity about?
unequal sharing of electrons between atoms bonded together covalently
What is polarity the property of?
property of the bond
How must the electrons in a bond between atoms that are the same be shared?
must be shared equally between the atoms
Why must the electron be shared equally in a bond between atoms that are the same?
both atoms have exactly the same electronegativity
What is the polarity of the bond between two of the same atoms like?
non-polar
How will the electrons be shared in a covalent bond between two atoms of different electronegativity?
electrons would not be shared equally between the atoms
How is the electron cloud described to be when the atoms have different electronegativities in the bond?
distorted
What relative charge would the atom with a higher electronegativity have?
relatively negative
What relative charge would the atom with a lower electronegativity have?
relatively positive
What is the polarity of the bond between atoms who have different electronegativities?
polar
What is the polarity of the bond like the greater the difference in electronegativity?
the more polar the covalent bond
How can you say a covalent bond has some ionic characters?
it may be going some way towards the separation of the atoms into charged ions
Is it possible to have ionic bonds with covalent characters?
yes
