Ionisation Energy

The removal of one or more electrons from an atom or molecule.

The energy required to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions.

Ionization energies are measured for gaseous atoms.

The definition specifies energy needed for 1 mole of atoms, not a single atom.

It is easier to form an ion.

More protons increase nuclear charge, strengthening attraction for electrons.

Electrons further from the nucleus experience weaker attraction.

Inner electron shells reduce the nuclear attraction felt by outer electrons.

There is a strong attraction between the electron and the nucleus, requiring more energy to remove the electron.

The energy required to remove additional electrons one by one from an atom.

The energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.

X⁽ⁿ⁻¹⁾(g) → Xⁿ⁺(g) + e⁻

It provides evidence for the shell structure of atoms.

Removing electrons creates an increasingly positive ion, reducing electron repulsion and strengthening nuclear attraction.

An electron is being removed from a shell closer to the nucleus.

Count the number of electrons removed before the first big jump to find the group number.

Count the points before each big jump from right to left to find the number of electrons in each shell, starting with the first.