Why does the ionization energy change when moving down a group of elements? The number of valence electrons increases.
The nuclear positive charge increases.
The energy levels are increasing.
The attractive force decreases as the atom gets larger.

The trends and exceptions to the trends in ionization energy observed includes;

B, ionization energy tends to increase across a period because the nuclear charge increases.

C, ionization energy tends to increase across a period because electrons are added to the same main energy level.

E, The ionization energies of elements in Group 13 tend to be lower than the elements in Group 2 because the full s orbital shields the electron, in the p orbital from the nucleus. 

Ionization energies measure the tendency of a neutral atom to resist the loss of electrons. It takes a considerable amount of energy, for example to remove an electron from a neutral fluorine atom to form a positively charged ion. 

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explanation:

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