ATOMIC STRUCTURE PERIODIC TABLE 2 Flashcards
What letter used to represent
shell number?
n
From which shell onwards is S
orbital present?
n = 1
From which shell onwards is
P-orbital present?
n = 2
From which shell onwards is
D-orbital present?
n = 3
From which shell onwards is
F-orbital present?
n = 4
What are the rules by which
electrons are arranged in the
shell?
● Electrons are added one at a time
● The lowest available energy level is filled first
● Each energy level must be filled before the next one can fill
● Each orbital is filled singly before pairing
● 4s is filled before 3d
Why does 4s orbital fill before
3d orbital?
4s orbital has a lower energy than 3d
before it is filled
What is the electron
configuration of krypton
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
How can the electron
configuration be written in
short?
The noble gas before the element is
used to abbreviate
Li → 1s2 2s1
Li → [He] 2s1
How are the elements
arranged in a periodic table?
Group number = number of electrons in
the outer shell
What is a period on a periodic
table?
The horizontal rows
What is a group on a periodic
table?
The vertical columns
How is the group number
related to the number of
electrons?
They are arranged in the order of
increasing atomic numbers
Does the group number
indicate horizontal or vertical
columns in the periodic table?
Vertical column
What is meant by periodicity?
The repeating trends in chemical and
physical properties
What change happens across
each period?
Elements change from metals to
non-metals
Define first ionisation energy.
The energy required to remove a mole of electrons from a mole of gaseous atoms
to form one mole of gaseous 1+ ions
under standard conditions
Write an equation for the first
ionisation energy of
magnesium.
Mg(g) → Mg+(g) + e-
What are the factors that affect
ionisation energy?
● Atomic radius
● Nuclear charge
● Electron shielding or screening
Explain the trend on this graph
First ionisation energy (kJmol) AGAINST Element
16| x
14|
12| x
10| x x
8 | x x
6 | x
4 | x
2 |
0 |_____________________________
Na Mg Al Si P S Cl Ar
● First Ionisation energy increases across period 3 because of:
○ Increased nuclear charge
○ Decreased atomic radius
○ Same electron shielding
● This means more energy is needed to remove the first electron.
● Dips at Al because the outer electron is in a 3p orbital, higher energy than 3s orbital → less energy needed to remove the electron
● Dips at S because one 3p orbital contains two electrons → repulsion between paired electrons → less energy needed to remove one
