Which of the following statements correctly explains why the first ionization energy generally increases from left to right across a period in the periodic table?
- A) The effective nuclear charge increases while inner-shell shielding remains relatively constant, resulting in a stronger electrostatic attraction to valence electrons.
- B) The number of occupied principal energy levels increases, placing valence electrons progressively farther from the nucleus.
- C) The shielding effect from core electrons increases significantly, diminishing the nuclear pull experienced by the outermost electrons.
- D) The atomic radius increases across the period, weakening the force needed to remove a valence electron.
