Actually, it is debatable. In singular possession, which is your case, some writers just put an apostrophe and others " 's ". In plural possession, it is certainly just an apostrophe.

Yes, the possesive for "Chavez" is "Chavez's". Here is a link to a page that I think will help.: https://www.bbc.co.uk/bitesize/topics/zvwwxnb/articles/zx9ydxs

Not really an expert, but I found this page https://www.thepunctuationguide.com/apostrophe.html which has an exception for nouns that seem plural, such as the United States’ lingering debt problem . Does not at first sight seem to be your case, but there is nothing else I see to explain it. Is "Chávez" plural?