7. PERIODICITY Flashcards
(35 cards)
Define Periodicity
A repeating trend in properties of the elements across each period of the periodic table
How is the periodic table arranged from left to right?
In order of increasing atomic number
Why do elements in the same group have similar chemical properties?
They have the same outer shell electron configuration
What is the trend across a period?
Each period starts with an electron in a new highest energy shell
For each period the s- and p- sub-shells are filled in the same way
What is the trend down a group?
Elements in each group have atoms within the same number of electrons in each sub-shell
-> This similarity in electron configuration gives elements in the same group their similar chemistry
Define First ionisation energy
The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
What 3 factors affect Ionisation energy?
- Nuclear charge
- Atomic radius
- Electron shielding
How does Nuclear charge effect ionisation energy?
The more protons in the nucleus, the greater the attraction between the nucleus and the outer electron
So the higher the ionisation energy
How does Nuclear charge change across periods
Across periods:
Atomic number increases so nuclear charge increases
So ionisation energy increases
How does Nuclear charge change down groups?
Down groups:
Atomic number increases so nuclear charge increases
So ionisation energy increases
How does Atomic radius affect ionisation energy?
The greater the distance between the nucleus and the outer electrons, the lower the nuclear attraction
So the lower the ionisation energy
How does atomic radius change across periods?
Across periods:
Atomic number increases which decreases atomic radius
Increasing ionisation energy
How does atomic radius change down groups?
Down groups:
Number of shells increases which increases atomic radius
Decreasing ionisation energy
How does electron shielding affect ionisation energy?
Inner shell electrons repel outer shell electrons, this shielding effect reduces the attraction between the nucleus and outer shell electrons
Decreasing ionisation energy
How does electron shielding change across periods?
Across periods:
Number of inner-shell electrons stays the same so nuclear attractions is the same so ionisation energy is similar
How does electron shielding change down groups?
Down groups:
The number of shells increases so the number of inner shell electrons increases, so nuclear attractions decreases
Decreasing the ionisation energy
What is the trend in first ionisation energy across a period?
- Nuclear charge increases
- Atomic radius decreases
- Similar shielding
These cause nuclear attraction to increase and so
First ionisation energy increases
What is the trend in first ionisation energy down a group?
- Nuclear charge increases
- Atomic radius increases
- Shielding increases
These decrease nuclear attraction (apart from nuclear charge however atomic radius has a larger effect) and so
First ionisation energy decreases
Define the second ionisation energy
The energy required to remove one electron from each [ion] in one mole of gaseous [1+ ions] of an element to form one mole of gaseous [2+] ions
Across a period where are the 2 places first ionisation energy drops?
- The start of the p-sub-shell
- The start of the electron pairing in the p-sub-shell e
Why does the first ionisation energy decrease at the start of the p-sub-shell?
The p-sub-shell has a higher energy than the s-sub-shell so the electron in the p-sub-shell is easier to remove
Why does the first ionisation energy decrease at the start of the electron pairing?
The paired electrons int he p-orbital repel each other, making it easier to remove an electron
What is the state of all metals (except mercury) at room temp?
solid
What is metallic bonding?
The strong electro static attraction between cations and delocalised electrons
