Topic A1 - Structure and Bonding
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As shell number increases…
energy level increases
What is an atomic orbital?
region around the nucleus that can hold up to 2 electrons with opposite spin
What shape is an s-orbital?
spherical
What shape is a p-orbital?
dumb-bell shape
How many p-orbitals are in each shell from n=2?
3
How many d-orbitals are in each shell from n=3?
5
How many f-orbitals are in each shell from n=4?
7
How many electrons can each shell hold?
n= 1, 2 electrons n=2, 8 electrons n=3, 18 electrons n=4, 32 electrons
What are the 3 main properties of ionic compounds?
• high MP and BP • dissolve in polar substances (water) • conduct electricity in liquid or aqueous state
What is a covalent bond?
strong electrostatic attraction between shared pair of electrons and the nuclei of the bonded atoms -overlap of atomic orbitals, each containing 1 electron to give a shared pair of electrons
The attraction of a covalent bond is…
localised - only between the shared electron pair
What is a dative covalent bond?
shared pair of electrons have been supplied by 1 of the bonding atoms only
As bond enthalpy increases…
the strength of the covalent bond increases
In a 3D shape of a molecule, a dotted line =
the bond going into the plane of the paper
What is electronegativity?
attraction of a bonded atom for the pair of electrons in a covalent bond
What are the 2 conditions for hydrogen bonding?
• electronegative atom (oxygen, nitrogen, fluorine) with lone pair of electrons • hydrogen atom attached to an electronegative atom (H-O, H-F, H-N)
How many hydrogen bonds can each molecule of water form?
4
Why does ice float in water?
-hydrogen bonds hold together water molecules apart in an open lattice structure -water molecules in ice are further apart than in water -solid ice is less dense than liquid water hence, ice floats in water
When water boils…
hydrogen bonds are broken completely
When ice lattice breaks…
rigid arrangement of hydrogen bonds in ice is broken