Structure Flashcards
What is electronegativity
the power of an atom to attract the pair of electrons in a covalent bond towards itself
why is there a decrease in electronegativity down the group
nuclear charge increases as more protons are being added to the nucleus
However, each element has an extra filled electron shell, which increases shielding
The addition of the extra shells increases the distance between the nucleus and the outer electrons resulting in larger atomic radii
Overall, there is decrease in attraction between the nucleus and outer bonding electrons
why is there an increase in electronegativity across a period
nuclear charge increases with the addition of protons to the nucleus
Shielding remains relatively constant across the period as no new shells are being added to the atoms
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
types of intermolecular forces
Induced dipole – London dispersion forces
Permanent dipole
Hydrogen Bonding are a special type of permanent dipole
what is stronger. Intramolecular or intermolecular
intramolecular such as covalent bonds
explain how induced dipole work
electron charge cloud in non-polar molecules or atoms are constantly moving
During this movement, the electron charge cloud can be more on one side of the atom or molecule than the other
This causes a temporary dipole to arise
This temporary dipole can induce a dipole on neighbouring molecules
When this happens, the δ+ end of the dipole in one molecule and the δ- end of the dipole in a neighbouring molecule are attracted towards each other
Because the electron clouds are moving constantly, the dipoles are only temporary
why is ice less dense than water
because the orientation of hydrogen bonds causes molecules to push farther apart
can giant covalent substance dissolve in any solvent
Giant covalent substances generally don’t dissolve in any solvents as the energy needed to overcome the strong covalent bonds in the lattice structures is too great
can polar covalent substances dissolve in non polar solvents
Polar covalent substances are unable to dissolve well in non-polar solvents as their dipole-dipole attractions are unable to interact well with the solvent
forces in metallic bonding
very strong forces between the positive metal centres and the ‘sea’ of delocalised electrons
why is ionic lattice neutral
Ions in a lattice are arranged in a regular repeating pattern so that positive charges cancel out negative charges
why do giant covalent lattices have high melting and boiling points
These compounds have a large number of covalent bonds linking the whole structure
A lot of energy is required to break the lattice
which giant covalent structure is hard and which one is soft
Graphite is soft as the forces between the carbon layers are weak
Diamond and silicon(IV) oxide are hard as it is difficult to break their 3D network of strong covalent bonds
are giant covalent compounds soluble
Most compounds are insoluble with water
conducting electricity in giant covalent structures
Graphite has delocalised electrons between the carbon layers which can move along the layers when a voltage is applied
Diamond and silicon(IV) oxide do not conduct electricity as all four outer electrons on every carbon atom are involved in a covalent bond so there are no freely moving electrons available
