The radius trend and the ionization energy trend are exact opposites. does this make sense?
define electron affinity. electron affinity values are both exothermic (negative) and endothermic (positive). however, ionization energy values are always endothermic (positive).

The radius trend and the ionization energy trend are exact opposites. Does this make sense?

The atomic radius is the distance from the center of the nucleus to the boundary of the surrounding shells of electrons. The ionization energy is the energy required to remove an electron from a neutral gaseous atom. If an atom has a larger atomic radius, the electrons are more separated from the nucleus and experience a weaker attraction force. Then, less energy is required to remove them from the atom. That's why the radius trend and the ionization energy trend are opposites.

Define electron affinity.

Electron affinity is the amount of energy released or spent when a neutral gaseous atom gains an electron to form an anion.

Electron affinity values are both exothermic (negative) and endothermic (positive). However, ionization energy values are always endothermic (positive). Explain.

When an atom gains an electron, it can absorb energy (endothermic process) or it can release energy (exothermic process). However, it is always necessary to provide an atom with energy to remove an electron, that is, it is always an endothermic process.

when [oh-] is 10-5  m, and [h3o+] is 10-9  m, the poh is 5 and ph is 9. again in both cases the sum of ph and poh is 14. however, the hydrogen ion concentration is not always going to be equal to exactly 1 x 10 raised to a negative number. for example, we skipped over the value of 2.0 x 10-7.