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What is an orbital?
region of space in an atom that can hold up to two electrons with opposite spins
How many orbitals in a p subshell?
3 orbitals
How many orbitals in a d subshell?
5 orbitals
When using ‘electrons in a box’ representation, what shape is usesd to represent the electrons?
opposite single sided arrows
What does the principal quantum indicate?
shell occupied by the electrons
What is the shape of the s orbital?
spherical
What is the shape of the p orbital?
dumbbell shaped
What are the rules by which electrons are arranged in a shell?
lowest available energy level filled first
each orbital fills singularly before pairing
4s before 3d
each energy level fills before the next one
Why does the 4s orbital fill before 3d?
4s is at a lower energy level than 3d
Which electrons are lost when an atom becomes a positive ion?
electrons in the highest energy levels
What is the electronic configuration of Krypton (electron number 36)?
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶
What is the electronic configuration of Magnesium (electron number 12)?
1s² 2s² 2p⁶ 3s²
What is first ionisation energy?
energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions
How does atomic radius affect ionisation energy?
greater atomic radius = smaller nuclear attraction = lower ionisation energy
How does nuclear charge affect ionisation energy?
greater nuclear charge = greater attractive force = higher ionisation energy
How does electron shielding affect ionisation energy?
greater shielding = smaller nuclear attraction = lower ionisation energy
What is electron shielding?
inner shell electrons repel outer shell electrons
What are the three main types of chemical bonds?
ionic
covalent
metallic
What is covalent bonding?
electrostatic attraction between a shared pair of electrons and the nuclei of the atoms
Which type of diagram is used to represent covalent bonding?
dot and cross diagram
What is average bond enthalpy?
enthalpy change when 1 mol of bonds is broken in gaseous atoms
What is a dative covalent bond?
both electrons are supplied by one atom
What are the two types of covalent structure?
simple covalent
giant covalent
What are some examples of simple covalent structures?
H₂O / CO₂ / NH₃
What is the bonding like in simple covalent structures?
atoms within the same molecule are held by strong covalent bonds, different molecules are held by weak intermolecular forces
Why do simple covalent structures have low melting and boiling points?
only small amount of energy is required to overcome the weak intermolecular forces
Why don’t simple covalent structures conduct electricity?
they have no free charged particles to carry charge
Simple molecular substances dissolve in what kind of solvent?
non-polar solvents
What are some bonding exceptions?
BF₃ - electron deficient
SF₆ - expansion of the octet (12 outer electrons on S, 6 covalent bonds)
What are the properties of giant covalent structures?
high melting and boiling points
insoluble
unconductive
Why aren’t giant covalent structures soluble in water?
the particles carry no charge so polar water molecules are not strongly attracted to them
Why don’t giant covalent structures conduct electricity?
there are no mobile ions or electrons free to carry the charge
Why do giant covalent structures have high melting and boiling points?
there are strong bonds between each molecule and so it would take a high amount of energy to break them
What is the exception (in terms of properties) to giant covalent structures?
graphite - delocalised electrons present between the layers are able to move freely and carry charge
What is ionic bonding?
electrostatic force of attraction between positive and negative ions
What does ionic bonding occur between?
metal and nonmetal
Why do giant ionic lattices conduct electricity when liquid but not when solid?
when solid the ions are in fixed positions, but in a liquid state the ions are mobile and so are free to carry charge
Why do giant ionic lattices have high melting and boiling points?
a large amount of energy is required to overcome the electrostatic bonds
Why are ionic compounds soluble in water?
water has a polar bond, H+ and OH- atoms are able to attract ions
What does the shape of a molecule depend on?
number of electrons in outer shell
bonded vs lone pairs
What is the shape of a molecule with two(2) bonding pairs and no lone pairs?
linear
What is the bonding angle of a molecule with two(2) bonding pairs and no lone pairs?
180°
What is the shape of a molecule with three(3) bonding pairs and no lone pairs?
trigonal planar
What is the bonding angle of a molecule with three(3) bonding pairs and no lone pairs?
120°
How many bonding and lone pairs does a linear molecule have?
2 bonding, 0 lone
What is an example of a linear molecule?
CO₂
How many bonding and lone pairs does a trigonal planar molecule have?
3 bonding, 0 lone
What is an example of a trigonal planar molecule?
BF₃
What is the shape of a molecule with four(4) bonding pairs and no lone pairs?
tetrahedral
How many bonding and lone pairs do tetrahedral molecules have?
4 bonding, 0 lone
What is the bonding angle in a tetrahedral molecule?
109.5°
What is an example of a tetrahedral molecule?
CH₄
What is the shape of a molecule with five(5) bonding pairs and no lone pairs?
trigonal bipyramidal
How many bonding pairs and lone pairs are in a trigonal bipyramidal molecule?
5 bonding, 0 lone
What are the bonding angles in a trigonal bipyramidal molecule?
120° / 90°
What is an example of a trigonal bipyramidal structure?
PCl₅
What is the shape of a molecule with six(6) bonding pairs and no lone pairs?
octahedral
How many bonding regions do octahedral molecules have?
6 bonding, 0 lone
What is the bonding angle in an octahedral molecule?
90°
What is an example of an octahedral molecule?
SF₆
What is the shape of a molecule with three(3) bonding pairs and one(1) lone pairs?
trigonal pyramidal
What are the bonding regions in a trigonal pyramidal molecule?
3 bonding, 1 lone
What is the bonding angle in a trigonal pyramidal molecule?
107°
What is an example of a trigonal pyramidal molecule?
NH₃
What is the shape of a molecule with two(2) bonding pairs and two(2) lone pairs?
bent
What are the bonding regions in a bent molecule?
2 bonding, 2 lone
What is the bonding angle in a bent molecule?
104.5°
What is an example of a bent molecule?
H₂O
What is the shape of a molecule with four(4) bonding pairs and two(2) lone pairs?
square planar
What are the bonding regions in a square planar molecule?
4 bonding, 2 lone
What is an example of a square planar molecule?
XeF₄
What is the bonding angle in a square planar molecule?
90°
By how many degrees does each lone pair reduce the bond angle?
2.5°
What is electronegativity?
the ability of an atom to attract the pair of electrons (electron density) in a bond
Does electronegativity increase or decrease down a group?
decreases - more shielding, atomic radius increases, charge density decreases
Does electronegativity increase or decrease across a period?
increases - atomic radius decreases, charge density increases
What is the most electronegative element?
fluorine - 4.0 on the Pauling Scale
What does it mean when a bond is non-polar?
the electrons in the bond are evenly distributed
How is a polar bond formed?
bonding atoms have a difference in electronegativity
What is an intermolecular force?
attractive force between neighbouring molecules
What are the types of intermolecular forces?
hydrogen bonding
induced dipole-dipole interaction
permanent dipole-dipole interaction
What is the strongest intermolecular force?
hydrogen bonding
What is induced dipole-dipole interaction?
when a polar molecule has an uneven distribution of electrons, this influences other particles as the electrons repel, forming an induced dipole
What is the weakest intermolecular force?
induced dipole-dipole
Are London forces greater in smaller or larger molecules?
larger because more electrons
What conditions are needed for hydrogen bonding to occur?
O-H, N-H, or F-H bond
lone pair of electrons on O, F, or N
Why is ice less dense than water?
in ice, water molecules are arranged in an orderly pattern, it has an open lattice with hydrogen bonds. in water, the lattice is collapsed and the molecules are closer together
Why does water have a higher melting/boiling point than expected?
hydrogen bonds are stronger than other forces so extra strength is needed to break the bonds
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