Chemistry Periodicity
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- Created by: I.m
- Created on: 22-12-12 20:29
How are the elements arrange in the periodic table?
Elements are arranged in order of increasing atomic number.
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What do the periods show?
Periods show repeating trends in physical and chemical properties.
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What does the period number correspond to?
The period number corresponds to the highest occupied energy level.
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What do groups show?
Groups have similar physical and chemical properties.
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What does the group number correspond to?
The group number corresponds to the number of electrons in the highest occupied energy level.
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What does the group number indicate?
The group number gives the number of electrons in the outer shell.
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What does the block which an element belongs to indicate?
The block which an element belongs to indicates the highest occupied sub-shell.
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Explain why elements in a group all react in a similar way.
Elements within the same group all react in a similar way. This is because chemical reactions involve only the outer shell electrons of an atom. Elements within a group have atoms with the same number of electrons in their outer shell.
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Define periodicity.
The trend in properties that is repeated across a period.
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What do periodic trends allow us to do?
Periodic trends allow us to make predictions about likely properties of elements based on their position in the periodic table.
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Explain the trend across a period.
Across a period number of protons increase so nuclear charge increase.Electrons are added to the outer shell so there is no increase in shielding or in the distance from the nucleus.Attraction between nucleus and outer electrons therefore increases.
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Explain the trend down a group.
Down a group no of shells increase so outer shell e-s are further from nucleus.There is more shielding due to more inner shell e-s being present.These 2 factors outweigh increase in nuclear charge so attraction between nucleus and outer e-s decrease
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What is the trend in atomic radius across a period?
Atomic radius decreases across a period. Across a period, nuclear charge increases as no of protons increase. Shielding is unchanged because e-s are added to the outer shell.Attraction between nucleus and outer e-s increases so atomic radius decrease
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What is the trend in atomic radius down a group?
Atomic radius incrs dwn a group.Dwn a group no of shels incr so outer shel e-s are frthr frm nuc.Shielding incrs due to mor inner shel e-s being prsnt.These 2 fctrs outwgh incr in nuc chrge so attrctin btwn nuc+outer e-s decrs so atmic rdius incrs dw
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Explain the trend in first ionisation energies across a period.
IE incrs across period.Nucl charge incrs as proton no incrs.Shielding is unchanged becse e-s are added to outer shell.This incs the attraction between nucleus and outer e-s so more energy needed to remove the outer e-s so 1st IE incrs across a period
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Explain the trend in first ionisation energies down a group.
IE dcrs dwn group.No of shels incrs so outer shel e-s frther frm nuc.Shlding incrs due 2 mor inner shel e-s being present.Thse 2 fctrs outwgh incr in nuc charg so attrc btwn nuc+outer e-s decrs.Thefre les enrgy need to remove outer e-s so 1st IE decr
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Explain the trend in boiling/melting points of elements in period 2 (from Li to B) and period 3 (from Na to Al) in terms of structure, bonding and forces.
Increase in boiling/melting point. These elements are metals (except B) so have metallic bonding and giant lattice structures. The forces of attraction between the positive metal ions and negative delocalised electrons is strong so boiling/melting po
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Explain the trend in boiling/melting points of element in period 2 C and period 3 Si in terms of structure, bonding and forces.
Atoms held together in a giant covalent structure by a network of strong covalent bonds. Boiling/melting points are very high because a lot of energy is needed to break the bonds.
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Explain the trend in boiling/melting points of elements in period 2 (from N to Ne) and period 3 (from P to Ar) in terms of structure, bonding and forces.
N₂, O₂, F₂, P₄, S₈ and Cl₂ have simple covalent molecular structures (Ne and Ar exist as single atoms). Between the molecules are weak Van der Waals’ forces which are easily broken hence the low boiling/melting point.
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Other cards in this set
Card 2
Front
What do the periods show?
Back
Periods show repeating trends in physical and chemical properties.
Card 3
Front
What does the period number correspond to?
Back
Card 4
Front
What do groups show?
Back
Card 5
Front
What does the group number correspond to?
Back
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