Chapter 7 Periodicity
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How are elements arranged in the current periodic table
• In order of increasing atomic (proton) number • In vertical columns called GROUPS • In horizontal rows called PERIODS
What is Periodicity
A repeating trend in properties of elements across each period
What is the periodic trend in electron configuration
The number of the period gives the number of the highest energy electron shell in an element’s atoms
What are Group 1 Metals called
Alkali metals
What are group 2 metals called
Alkaline earth metals
What is the first ionisation energy
The energy required to remove one electron from each atom in one mole of gaseous atoms of an element. [UNITS: kJ mol-1]
What is the equation for the first ionisation energy of element X
X(g) → X+(g) + e-
What factors affect ionisation energies
• Atomic Radius • Nuclear Charge • Inner Shell Shielding
How does Atomic radius affect ionisation energy
The greater the distance between the nucleus and the outer shell electrons, the weaker the nuclear attraction between the nucleus and the outer electrons
How does Nuclear Charge affect ionisation energy
The more protons there are in the nucleus of an atom, the greater the nuclear attraction between the nucleus and the outer shell electrons
How does inner shell shielding shielding affect ionisation energy
Inner shell electrons repel outer shell electrons. This repulsion called the shielding effect reduces the attraction between the nucleus and the outer electrons
As you go down the group do the first ionisation energies increase or decrease
Decrease
Why do the first ionisation energies decrease down a group
• Atomic radius increases • More inner shells, so shielding increases • Nuclear attraction decreases