Learn Portuguese (Portugal): O impacto emocional é enorme.

It is formed by taking the base of the noun emoção (emotion) and adding the suffix -al. In Portuguese, -al is frequently added to nouns to create adjectives meaning "relating to" or "characteristic of" that noun. It works exactly like the English "-al", making words like natural or cultural very easy to recognize.

Neither emocional nor enorme ends in -o or -a. How do they agree with the masculine noun impacto?

Both of these are gender-neutral adjectives. In Portuguese, adjectives ending in -al (like emocional) or -e (like enorme) do not change form between masculine and feminine nouns. They only change for the plural. If the noun were plural, they would become emocionais and enormes.

Could I use the word emotivo instead of emocional here?

Not quite, though it is a common mix-up! Emocional simply means "relating to the emotions" (such as a psychological impact). Emotivo usually describes a person who is easily moved to tears, or something that triggers strong feelings (like a touching movie). Since we are classifying the category of the impact, emocional is the right choice.

Why does the sentence use é (from the verb ser) instead of está? Isn't an impact just a temporary event?