Periodic Table Flashcards
Why is there a decrease in atomic radius of the element across a Period?
Nuclear charge increases as the number of protons increases, the shielding effect remains approximately the same as the number of inner electron shells is the same, effective nuclear charge increases, valence electrons are more strongly attracted to the nucleus, atomic radius decreases
Down a group, does electronegativity increase or decrease?
Decrease. Nuclear charge increases and the shielding effect increases, outweighs, effective nuclear charge decreases, and attraction for bonding electrons by the nucleus decreases.
Define electronegativity
Ability of an atom to attract electrons in a covalent bond towards itself.
Across a period, does electronegativity increase or decrease?
Increase. Nuclear charge increase and shielding effect remain approximately the same, effective nuclear charge increase, attraction for bonding electrons by nucleus increases.
Across period 3, why does the melting point increase from Na to Al?
There is an increasing number of delocalised valence electrons.
There is an increase in charge density of cations due to an increasing charge and decreasing cationic size.
Giant metallic structure, high melting point
Why does Silicon have the highest melting point in period 3?
It has a giant molecular structure with Si atoms held together by numerous strong electrostatic attraction between 2 positive nuclei and a shared pair of electrons.
Giant molecular, very high melting point
Across period 3, explain the melting point of P4 to cl2.
Melting point of S8 is higher than that of P4 as sulfur exists as S8 molecules and phosphorus exists as P4 molecules. S8 molecule has a larger and more polarisable electron cloud compared to P4 molecule, id-id interactions between S8 are stronger compared to that of P4.
Simple molecular, low melting point
Define volatility of a substance
Measure how readily a substance vaporises. It has an inverse relationship with boiling point.
Explain the trend in the volatility of group 17 elements
Halogens exist as simple covalent molecules with simple molecular structures and are non-polar.
The strength of id-id interactions between molecules increases as size of electron cloud in each molecule increases.
Amount of energy required to overcome id-id interactions between molecules to vaporise the halogen increases.
Bonding present in metallic bonds.
Strong electrostatic forces of attraction between a lattice of positive ions and delocalised electrons.
Why do oxides formed by period 3 elements become less ionic and more covalent?
The difference in electronegativity between the elements decreases across the period. Element becomes less likely to lose an electron to a more electronegative element, O, to form an ionic bond rather prefer to share electrons to form covalent bond.
Bonding present in covalent bonds.
Electrostatic attraction between a shared pair of electrons and the 2 positively charged nuclei of the 2 atoms.
Bonding present in ionic bonds
Electrostatic attraction between oppositely charged ions.
Bonding present in metallic bonds
Strong electrostatic forces of attraction between a lattice of positive ions and delocalised electrons.
How to separate Na, Mg and Al?
Na can be separated by adding water to mixture. NaOH is formed, Mg and Al insoluble in water.
Mg and Al separated by adding NaOH, Mg insoluble but Al soluble, dissolves to give a colourless solution.
