It might help to think of verbs like danken as "jemandem Dank geben" (to "give thanks" to someone) or helfen as "jemandem Hilfe geben" (to give help to someone). "Jemandem Dank geben" is not something a native speaker would say, but maybe it helps to understand why these verbs require a Dativ object: jemandem [=Dativ] Dank [=Akkusativ] geben. Can't guarantee that this will work with all verbs though.
I Looked it up, and there seem to be about 50 German verbs that always take the dative case.
According to the website: http://german.about.com/library/verbs/blverb_dativ.htm there are 12 common German verbs that always take the dative case.
"additional dative verbs that are perhaps less common and not listed in Part One. However, many of the verbs in this chart are important German vocabulary and should also be learned.
I hope this helps.
PS: the second page/website also has a couple of genitive verbs. MY advice is to not worry about them now, since we have learned about the genitive case yet.
Yes, but there are limited circumstances where it'd be warranted outside of formal situations. You'd say "I thank you" to give emphasis to the person, to show that you really really appreciate whatever you're thanking the person for. Or you might say it if you have a huge amount of reverence or respect for the person you're thanking. In the majority of contexts it would come across as being too formal/excessive.
This has been of great value to me regarding sie, dir, euch, ihn etc etc
This is actually easy to understand if you speak portuguese. In english you say 'I like you' and 'I thank you', whereas in portuguese you have to say ' eu gosto de ti' for the first case ( 'de ti' meaning you) and 'eu agradeço-te' for the second case ( '-te' meaning you). We have different ways of addressing ourselves to people
"Ich danke ihnen" (not capitalized) would be "I thank them". "Ich danke Ihnen" (capitalized) is "I thank you" (formal). "Ich danke dir" is "I thank you" (not formal). "Ich danke sie" doesn't exist ("danken" requires Dativ). It's either "Ich danke Ihnen" (capitalized, see above) or "Ich danke ihr" ("I thank her").
If you hear someone say [ich danke ihnen] and you have no context at all, it is impossible to tell if it means "I thank you" (formal singular), "I thank you (all)" (formal plural) or "I thank them". So in a listening exercise, all of those should be accepted IMO.
In an actual conversation it's pretty much the same. Without any context, you just can't tell what it means. But then again, an actual conversation should have enough context so that you know what the other person tries to say.
Wait a minute . . . Shouldn't the correct translation be: "I thank them."? Doesn't "danken" call for dative case, so "I thank you." would be "Ich danke euch/dir." right? Ooops . . . I didn't notice the capitalized "I." OK, "Ich danke Ihnen." DOES mean "I thank you." when the "you" in question is formal. sigh . . . I'll get this quicker eventually . . . I hope. Wait another minute! The question accepts "I thank you all." as a correct answer; but would not that be "Ich danke euch."?