How can radiation negatively ionize an atom?

Question

Ionizing radiation, as I've learnt it, ionizes an atom by supplying enough energy to essentially "knock" an electron off the atom — that is, by exciting the electron to a level that is gets freed from the atom it was previously bound to. However, I had this belief contested by a Youtube video, whose host said that:

[...] (the argon) atom can be made negatively charged by having an electron put on it [...]

How does that work? How can radiation negatively ionize an atom, not through the removal of a proton (like is discussed in this thread) but rather by the addition of an extra electron (or more)?

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The entire context here is about ionizing radiation and how it could ionize an atom (in this case, Argon) negatively so an answer explaining that would be perfect.

Answer 1

Confusion here between ionizing radiation and ionization/ions in general.

Ions are atoms that lack electrosn or have some extra ones, which makes them positively/negatively charged.

Ionizing radiation kicks an electron (or more) from an atom, producing a positively charged ion.

Ionization can be achieved by different means, not necessarily via radiation. E.g., a $NaCl$ salt dissolved in water will separate into ions: $$ NaCl \leftrightarrow Na^{+}+Cl^{-} $$

In a gas ions can arise from atoms capturing electrons, e.g., if these electrons were previously released by other atoms as a result of ionizing radiation. In gas discharge tubes the ions may also arise from the electron flow, atomic collisions, or molecules torn apart by electric field.