Periodicity. Flashcards
Define periodicity.
Periodicity is the repeating pattern of physical or chemical properties going across the periods.
How are elements classified into s, p, d blocks.
Elements are classified as s, p or d block, according to which orbitals the highest energy electrons are in.
Period 2 = Li, Be, B, C, N, O, F, Ne
Period 3 = Na, Mg, Al, Si, P, S, Cl, Ar.
State and explain the trend in atomic radius across a period. Graph this and state the exception here.
Atomic radii decrease from left to right across a period, because the increased number of protons create more positive charge attraction for electrons which are in the same shell with similar shielding.
Exactly the same trend in period 2 and 3.
Exception of noble gasses which are weird. `look that up actually.
Write a six mark answer , supported by a graph, for the change in first ionisation energy across a period.
There is a general trend across to increase. This is due to increasing number of protons as the electrons are being added to the same shell.
There is a small drop between Mg + Al. Mg has its outer electrons in the 3s sub shell, whereas Al is starting to fill the 3p subshell. Al’s electron is slightly easier to remove because the 3p electrons are higher in energy.
There is a small drop between phosphorous and sulfur. Sulfur’s outer electron is being paired up with an another electron in the same 3p orbital.
When the second electron is added to an orbital there is a slight repulsion between the two negatively charged electrons which makes the second electron easier to remove.
Consider trend in second ionisation energy. weird one ALSO THINK ABOUT NAMES of the blocks in the table.
. Noble gasses in relation to atomic radius.
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What two periods can the periodicity principles be applied to interchangeably. Follow same trends.
Period two and three will follow the same trends across the period they will just use different elements obviously.
Remember hydrogen is in period 1 with helium.
Draw a graph for melting and boiling point on the same graph against the elements across period 3. State what is the only real difference in the shape of the two graphs.
Melting point is the more common graph you would need to draw which rises up to silicon and then falls after. There is a subtle difference in the graph for boiling point where aluminium is actually higher than silicon and so you but then it will still follow all other same patterns.
For Melting point the peak is for macromolecular and for boiling point the peak is for strongest metallic bonding.
In what type of property would you leave out the noble gasses in terms of the trend and which would you still consider them as being a part of. State why the noble gasses are excluded from this form of measure.
The noble gasses should be excluded when thinking about electronegativity. Hence Fluorine is the most electronegative atom and not Neon obviously.
Exclude also when thinking about atomic radius because they go all weird.
include when thinking about ionisation energy.
In what type of property would you leave out the noble gasses in terms of the trend and which would you still consider them as being a part of. State why the noble gasses are excluded from this form of measure.
The noble gasses should be excluded when thinking about electronegativity. Hence Fluorine is the most electronegative atom and not Neon obviously. Electronegativity is the ability of an atom to gain an electron. … Since the noble gases already have eight electrons in their outer shells, they dont wan’t to attract any more. Since electronegativity measures the amount of attraction between an atom and an electron in a covalent bond, noble gases do not have electronegativity.
Also exclude from atomic radius trend.
Give the elements that you will see a drop in first ionisation energy for period 2 and 3.
Period 2: Drop from Be to B and N ton O
Period 3: Drop from Mg to Al and P to S.
Explain the change in melting point for the first three elements across period 2. refer to how such species are classified.
For Na, Mg, Al- Metallic bonding : strong bonding – gets stronger the more electrons there are in the outer shell that are released to the sea of electrons. A smaller sized ion with a greater positive charge also makes the bonding stronger. Higher energy is needed to break bonds.
Give the classification of the there elements in period 3 that cause a sharp drop in both melting and boiling point across period 3. Give the formula of each molecule.
Cl2 (g), S8 (s), P4 (S)- simple molecular.
Give the formula of the simple molecular compounds that cause the drop in melting and boiling point across period 3.
Cl2 (g), S8 (s), P4 (S)
When considering melting and boiling points across a period what is the name of the type of molecule that caused the lowest melting or boiling point for that group.
Both the noble gasses Ne for period 2 and also Ar for period 3 are monoatomic weak van der waals between atoms.
Draw a graph for the change in atomic radius across period 3.
Gradual curve down apart from the noble gasses.
