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What does the principal quantum number represent?
Indicates the shell that the electrons occupy
If the principal quantum number is higher, what does this mean?
The the shell is further away from the nucleus
What is the equation that determines the number of electrons in each shell?
2(n^2), where n = the shell
What are shells also regarded as?
Energy levels
What occurs to the energy as the shell number increases?
Energy also increases
How many electrons are in the first four shells?
2, 8, 18, 32
What is an atomic orbital?
A region around the nucleus that can hold up to two electrons with opposite spins
What are the three main rules of orbitals?
- An orbital can hold up to two electrons only
- There are four types of orbitals
- Each orbital has a different shape
What are the four types of atomic orbitals?
- S orbitals
- P orbitals
- D orbitals
- F orbitals
What do models visualise orbitals as?
A region in space where there is a high probability of finding an electron
What is the equation that determines the number of electrons in a shell?
2n^2
What is the shape of a s orbital?
A spherical shape is seen
What is the shape of a p orbital?
A dumbbell shape is seen
How many electrons can any one orbital hold?
Any orbital from any subs hell can only hold up to two electrons
How many orbitals are in the S subshell?
1 orbital per S subshell
How many electrons can an S subshell hold up to?
2
How many orbitals does a P subshell have?
3 orbitals on different planes;
- Px
-Pz
- Py
How many electrons can the p shell hold up to?
Up to 6 electrons (as it has three orbitals)
How many orbitals does a d subshell have?
5 orbitals
How many electrons can a d shell hold up to?
Up to 10 electrons
How many orbitals does an f subshell have?
7 orbitals
How many electrons can an f subshell hold up to?
Up to 14 electrons
At n=1, what are the sub shells present?
1s2
At n=2 for noble gases, what are all of the sub shells present?
(1s2), 2s2, 2p6
At n=3 for noble gases, what are all of the sub shells?
1s2, 2s2, 2p6, 3s2, 3p6, 3d10
What is a special rule in n = 4 upon the arrangement of energy levels?
3d10 has a higher energy level than 4s2 therefore 4s2 becomes filled first
(if it goes past 3d10, which in n = 4 at a noble gas, it will)
For n = 4 of noble gases, what are all of the sub shells?
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 4d10, 4f14
How are electrons arranged in an orbital?
Electrons are in a pair with opposite spins
Why do electrons in orbitals have opposite spins?
1) Electrons are negatively charged
2) Electrons therefore repel each other
3) Two electrons therefore have opposite spins to help counteract repulsion between negative charges of each electron
In a box filling diagram, what does a box represent?
An orbital
What does an arrow represent in a box filling diagram?
An electron
In a box filling diagram, how are orbitals arranged?
- One arrow faces up
- One arrow faces down
How does each electron fill the orbitals? Describe why this is before you explain how each box has their orbitals filled
- One electron fills each orbital in a subshell first
- This is due to the need to prevent repulsion
- One arrow fills each box before a second arrow starts filling each box
How does the 4s sub shell fill and empty through addition/loss of electrons?
- 4s sub-shell fills before the 3d subshell
- 4s sub-shell empties before the 3d subshell
When an element becomes a positive ion, what occurs in the electron configuration of sub shells?
Electron configuration decreases in electrons and therefore number
When an element becomes a negative ion, what occurs in the electron configuration of sub shells?
Electron configuration increases in electrons and therefore in number
What is the electron configuration of oxygen?
1s2 2s2 2p4
What is the electron configuration of Potassium?
1s2, 2s2, 2p6, 3s2, 3p6, 4s1
What is another electron configuration of potassium other than the normal electron configuration? (shorthand notation)
[Ar]4s1
What are the three types of chemical bonding?
- Ionic bonding
- Covalent bonding
- Metallic bonding
What is an ionic bond?
Strong electrostatic attraction between positive metal ions and negative non-metal ions. Can only occur between metal and non-metals
What structure is formed from ionic bonding?
A giant ionic lattice forms
How is a giant ionic lattice formed? (Steps)
1) Each ion is surround by oppositely charged ions
2) Each ion attracts an oppositely charged ion
3) This forms the giant ionic lattice
Why are most ionic bonds solid at room temperature?
There is insufficient energy to overcome the strong electrostatic forces between the oppositely charged ions
Do most ionic compounds have high or low melting points? Why is this?
Most ionic compounds have high melting points;
Lots of thermal energy is required to overcome the strong electrostatic attraction between oppositely charged ions in the giant ionic lattice
What is the trend of melting points and boiling points as the lattices of ions have a greater charge?
Melting points and boiling points increases
Describe and explain the solubility of ions.
- Ions can dissolve in polar solvents such as water which has polar OH groups
- Polar water molecules breaks down the lattice and surrounds each ion
What two main processes are needed for solubility?
- Relatively weak strengths of attractions within the giant ionic lattice
- Ionic lattice to be broken down
- Water molecules must attract and surround the ions
Dot and cross of sodium oxide:
2Na --> 2Na+ + 2e-
O + 2e- --> O2-
It is true that as ionic charge increases, solubility decreases?
This concept needs to be treated carefully,
- True for ionic compounds
However predictions shouldn't be made easily.
Can ions conduct electricity as a solid? Explain your choice (In steps).
No, it cannot;
- Ions are held in fixed positions within a lattice
- Therefore ions as a solid are non-conductors
- Ionic compounds therefore do not have any mobile charge carriers to conduct charge
Can ions conduct electricity as a liquid (or dissolved in water)? Explain your choice.
Yes, it can;
- Solid ionic lattice breaks down
- Ions are now free to move as mobile charge carriers
- Ionic compound is now a conductor of electricity in the liquid and aqueous state
What is a covalent bond?
Strong electrostatic attraction between a shared pair of electrons and the nuclei of all bonded atoms
Between what atoms can covalent bonding take part in?
- All non-metals
- Non metal compounds
- Polyatomic componds
What is a covalent bond in terms of orbitals?
Covalent bond is the overlap of atomic orbitals with each containing one electron to form a shared pair of electrons.
Why are covalently bonded atoms described as molecules?
As the attraction of a covalent bond is localised
How does covalent bonds accounting to electrons contrast to ionic bonds?
Covalent bonds share electrons. Ionic bonds transfer electrons.
What are lone pairs?
Pairs of electrons not involved in bonding but can influence the chemistry of a molecule
Dot and cross diagram of ammonia:
What is the octet rule? (What is it, why is it important)
- Sharing electrons gives both atoms a full valence shell of a maximum of eight electrons
- Arrangment is the same of a noble gas as it is the most stable electron arrangement.
What is an expansion of the octet rule?
When more than eight electrons can bind covalently more than the stable target of a noble gas
What occurs in a double bond?
How can carbon dioxide molecule be seen in multiple bonds?
Forms two double bonds with two oxygen atoms.
What is a dative covalent bond?
A covalent bond where a shared pair of electrons has been supplied by just one of the bonding atoms
What is a dative covalent bond also known as?
A coordinate bond
What is a great way to spot potential dative bonds?
If the atom before the covalent bond possessed a lone pair.
How are dative bonds represented in dot and cross diagrams?
Instead of a stick an arrow is used
How can oxonium ions be formed from hydrochloric acid?
HCl (g) + H2O --> H3O+(aq) + Cl-(aq)
How is an oxonium ion represented in a dot and cross diagram?
Why can the octet rule sometimes not be achieved?
- There are not enough electrons for an octect
- Expansion of the octet
When is the expansion of the octet rule possible?
From the n = 3 shell, AKA when the d sub shell becomes available
What is an example of when there aren't enough electrons for an octet to form?
Boron trifluoride
What is the dot and cross structure of boron trifluoride?
How could the octet rule be improved?
- Unpaired electrons pair up
- Maximum number of electrons that can pair up is equivalent to the number of electrons in the outer shell
What is the average bond enthalpy?
A measure of the average energy needed to break a bond
Would the average bond enthalpy that is endothermic be negative or positive?
Positive, indicating how much energy the molecules have received
Would the average bond enthalpy that is exothermic be negative or positive?
Negative, indicating how much energy the molecules has released to the environment
What are two types of covalent bonding structures?
- Giant covalent lattice
- Simple covalent lattice
Are covalently bonded molecules able to conduct electricity?
No, neither structure is able to conduct electricity as there are no free charged particles that aren't in fixed positions
What is the one exception to the rule of covalent structures not being able to conduct electricity?
Graphite; giant covalent structure
What is the solubility properties of simple covalent structures?
Generally are only able to be soluble in non-polar substances (i.e. hexane solvent)
Water is one of some exceptions to this as it undergoes hydrogen bonding.
What is the solubility properties of giant covalent structures?
All giant covalent structures aren't soluble in polar or non-polar substances
What are the melting and boiling points of simple covalent structures?
Very low meting and boiling points relatively as intermolecular forces are weak
What are the melting and boiling points of giant covalent structures?
Relatively high due to various intermolecular forces
What are the three main examples of giant covalent structures?
- Graphite
- Diamond
- Silicon dioxide
What are the features of electron pair repulsion theory?
- Shape of a molecule or ion is determined by the number of electron pairs in the outer shell
- Electron pairs repel one another so they are as far as possible
- Arrangement of electron pairs minimises repulsion and holds the bonded atoms in a define shape
- Different number of electrons result in different shapes
What types of electrons affects the shape of a molecule or ion?
- Bonded pairs
- Lone pairs
How are wedges represented in visualisation of 3D structures of molecules and ions?
- Solid line; Bond Is on a normal plane and it right angled away from you
- Solid wedge; Bond is coming towards you
- Dotted wedge; Bond is coming away from you
How does a lone pair affect the bond shape and angle?
- Occupies more shape
- Lone pair repels more strongly than a bonding pair
Which trumps in overall electron repulsion; lone pairs or bonding pairs?
Lone pair/Lone pair beats;
Lone pair/Bonding pair which beats;
Bonding pair/Bonding pair
In terms of degrees, what is the decrease of bond angle does each lone pair give?
2.5 degrees
What are the 6 ascending order, of the name of the shape, of increasing the number of bonded electron pairs in the outer electron shell?
- 1 bonded pair; linear
- 2 bonded pairs; linear
- 3 bonded pairs; trigonal planar
- 4 bonded pairs; tetrahedral
- 5 bonded pairs; trigonal bipyraimid
- 6 bonded pairs; octahedral
What is the bond angle in linear?
180 degrees
What is the bond angle in trigonal planar?
120 degrees
What is the bond angle in tetrahedral?
109.5 degrees
What is the bond angle in trigonal bipyramid?
90-120 degrees
What is the bond angle in octahedral?
90 degrees
What are the two exceptions to naming shapes of molecules, where lone pairs are added?
107 degrees (one lone pair); Pyramidal
104.5 degrees (two lone pairs); Non-linear
What is an example of a pyramidal molecule?
Ammonia
What is an example of a non-linear molecule?
Water
