Periodicity Flashcards
How does the radius change across the period?
The radius decreases
Because the increase in protons therefore increase in nuclear attraction
So electrons feel stronger attraction and are pulled closer: but all electrons are in the same shell so no effect of increase in shells nor shielding
Does the increasing electrons affect the atomic radius ACROSS THE PERIOD?
The increasing electron-electron repulsion by adding electrons does NOT affect the radius as its being added to the same shell
How does the atomic radius change with the group?
Increases as you go down
Because there are more shells and more shielding which increases atomic radius
Overcomes increase in nuclear charge that pulls electron shells towards nucleus
Does the number of protons affect the radius of an atom as you go down the group?
No because effect of more shells in an atom
outweighs this effect
Valence electrons
Outer shell electrons
Melting point in metals across the period
Increases because:
Greater number of valence electrons = high melting point
Shorter atomic radius = high melting point
Why does the melting point increase in metals if there are more valence electrons?
Because in metallic bonding there are more electrons are DONATED per atom into the sea or delocalised electrons
Electrostatic attraction between these electrons and nucleus is greater so therefore more energy required to break the bond
Outer electron configuration of group 1
ns¹
n = the period that specific element is in
Outer electron configuration of group 2
ns²
n = the period that specific element is in
Outer electron configuration of group 3
ns² np¹
n = the period that specific element is in
Outer electron configuration of group 4
ns² np²
n = the period that specific element is in
Outer electron configuration of group 5
ns² np³
n = the period that specific element is in
Outer electron configuration of group 6
ns² np⁴
n = the period that specific element is in
Outer electron configuration of group 7
ns² np⁵
n = the period that specific element is in
Outer electron configuration of group 8
ns² np⁶
n = the period that specific element is in
Groups
Vertical columns in periodic table that all contain the same outer electron configuration
Periods
Horizontal rows in periodic table that all contain the same quantum levels that have electrons
Blocks
Dividing the periodic table into 3 by sorting each group into a different block
S block
Groups 1 and 2
The highest energy electron (outer shell electrons) are in an s orbital
D block
All elements between Sc —> Zn
Y —> Cd
As you go across the period, the number of electrons in the d sub shell increases
P block
Groups 3, 4,5, 6, 7, 8
Highest outer electron is in the p orbital
Overall ionisation trend across periods
Increases as you go from left to right
Then sudden drop when moved to the next row which is further down the group
What are the anomalies in ionisation trends across the period?
It DECREASES between Be and B/ Mg and Al (same reason)
It DECREASES between N and O/ P and S (same reason)
When following the ionisation trend it should increase
Why is there an anomaly in ionisation energy between Be and B?
Although nuclear charge of the B atom is greater than Be atom,
Outer B electron has more energy (since it is in a 2p orbital unlike in the 2s orbital for Be)
So the energy required to remove this electron is less than that required to remove a 2s electron from a beryllium atom so IE decreases
Also the 2p electron in boron experiences greater electron–electron repulsion (so greater shielding) because there are two inner electron sub-shells as opposed to only one in the beryllium atom
