Answer:

The energy needed to remove one or more electrons from a neutral atom to FORM a positively charged ion is a physical property that influences the chemical behavior of the atom. By definition, the first ionization energy of an element is the energy needed to remove the OUTERMOST, or highest energy, electron from a neutral atom in the gas phase.

Explanation:

The magnitude of the first ionization energy of hydrogen can be BROUGHT into perspective by comparing it with the energy given off in a chemical reaction. When we burn natural gas, about 800 kJ of energy is released per mole of METHANE consumed.

CH4(g) + 2 O2(g) -----> CO2(g) + 2 H2O(g)     deltaHo = -802.4 kJ/mol

The thermite reaction, which is used to weld iron rails, gives off about 850 kJ of energy per mole of iron oxide consumed.

Fe2O3(s) + 2 Al(s) -----> Al2O3(s) + 2 Fe(l)     deltaHo = -851.5 kJ/mol

The first ionization energy of hydrogen is half again as large as the energy given off in either of these reactions.