Periodicity Flashcards
Meaning of periodicity
The occurrence of patterns in the periodic table
periodicity across a row
The atomic number increases for each successive element and the number of energy levels is the same
periodicity down a group
An occupied electron energy level is gained
down a group atomic size/covalent radius
Increases
across a row atomic size/covalent radius
Decreases
What is covalent radius
half of the distance between the nuclei of two bonded atoms of an element
Why is there is no covalent radius data for the noble gases
because they are monatomic elements
Why does covalent radius increase when going down a group
elements within the same group have one more occupied energy level as you go down the group
Why does covalent radius decrease when going across a period
Atoms within the same period have an increased proton in the nucleus going down each element. The increased positive charge on the nucleus increases the attraction for the electron in the outer energy level and they are pulled closer to the nucleus, making atoms smaller
First ionisation energy
the energy required to remove one electron from each atom of one mole of gaseous atoms
Second ionisation energy
the energy required to remove one electron from each singly positive ion of one mole of the gaseous ions
What state symbol is essential in ionisation
g
Is ionistion endothermic or exothermic
Endothermic
Ionisation down a group
decrease
Ionisation across a period
increase
Cause of Ionisation down a group
One more occupied energy level
Cause Ionisation across a period
Increased number of protons
Explained Cause of Ionisation down a group
The electron removed is further from the nucleus so the electron is more shielded. The weaker electrostatic attraction makes it easier to remove the electron.
Explained Cause Ionisation across a period
The increased positive charge increases attraction so it requires more energy to remove the electrons.
Why are Second and third ionisation energies larger than the first
the extra positive nuclear charge(s) has greater electrostatic attraction for the outer electrons and therefore more energy is required to remove the electrons.
What is Electronegativity
Electronegativity is a measure of the attraction an atom involved in a bond has for the electrons of the bond.
What does higher electronegativity mean
The higher electronegativity, the more strongly the nucleus attracts electrons towards it.
electronegativity down a group cause
One more occupied energy level
electronegativity across a period cause
Increased positive charge on the nucleus
Electronegativity down a group
decrease
Electronegativity across a period
increase
Electronegativity down a group explained
The electron removed is further from the nucleus so the electron is more shielded. This means there is weaker electrostatic attraction
Electronegativity across a period explained
The nucleus has a stronger electrostatic attraction for the electrons.
Why breaking full shells takes more energy
-Electrons are closer to the nucleus
-Electrons are less screened from the nucleus as there are fewer inner electron energy levels
Therefore there is more electrostatic attraction
