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When do we have to use roman numerals in the name of a compound?

Answer 1

Roman numerals are used in naming ionic compounds when the metal cation forms more than one ion. The metals that form more than one ion are the transition metals, although not all of them do this.

For example, copper can form #"Cu"^(+)"# ions and #"Cu"^(2+)"# ions. If they combine with chlorine, we can have #"CuCl"# and #"CuCl"_2"#. The first compound is composed of copper 1+ ions bonded to choride 1- ions. It's called copper(I) chloride. The second compound is composed of copper 2+ ions bonded to chloride 1- ions. It's called copper(II) chloride.

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Answer 2

Wyatt Adkins

When an element can have more than one oxidation state, Roman numerals are used in compound names to represent the state of oxidation for that element.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.