# Multi-Valent Transition Metals and Polyatomic ions.

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Multi-Valent Transition Metals and Polyatomic ions

Subscripts and Superscripts Superscripts (above) = charge (+ or -) of the ion Cl -1 or Ca +2 Subscripts (below) = the number of ions Cl 2 or H 4

Transition Metals: Nearly all the transition metals are able to form more than one cation or are multi-valent. Ex: iron can form Fe 2+ and Fe 3+. Given the formula of an ionic compound you can use the reverse cross-over method to determine the charge of the cation. Ex: FeCl 3

Scientists use two ways to name these type of compounds: Stock System Classical System

Classical System: We will not use the classical system for grade 10 science. We will only look at it and how it works. The classical system is based on latin names for elements. Ex: iron is ferrum. We add an “ic” to the end of this to indicate the higher charge and we add an “ous” to the end to indicate the lower charge. Ex: Iron

Stock System: The charge of the cation is written in brackets as a roman numeral. Ex: Fe 3+ would be iron (III) and Fe 2+ would be iron (II). Remember roman numerals: 1- (I), 2- (II), 3-(III), 4-(IV), 5-(V).

Example: Both CuO and Cu 2 O are real compounds We know that O always has a charge of -2 For CuO, we know that it is the Cu +2 ion (sum to zero)  copper (II) oxide And for the Cu 2 O, we know that there is 2 x the Cu +1 ion (to sum to zero)  copper (I) oxide

Try to write names for these (don’t forget the roman numberial for the metal) : CrO Au 3 P SnCl 4

Given the name we can write the formula: Nickel (III) bromide We know that Br is always Br -1 We also know that this is the Ni 3+ ion (it tell us in the brackets) Therefore we need 3 x Br -1 with Ni 3+ for the compound to be neutral (sum to zero)  NiBr 3

Try these: lead (II) chloride mercury (I) arsenide cobalt (II) chloride.

Quote of the day: “Our young people aren’t so bad; it’s just they have more critics than models.” Anon

Polyatomic Ions Have a charge ( + or - ) Consists of two or more non- metal atoms (or metal complex) joined by a covalent bond Act as a single unit

Polyatomic Ions See your table of ions on the periodic table for a list Please add ammonium: NH 4 + to the list

Write names for ionic compounds containing polyatomic ions: Na 2 CO 3 KOH Sn 3 (PO 4 ) 4

Writing chemical formulas for ionic compounds containing polyatomic ions: (remember to use parentheses to indicate the correct number of ions) 1. ammonium sulfide 2.lead (IV) hydrogen carbonate 3.calcium hydroxide 4.magnesium nitrate

Practice: handouts

Practice: (use stock system) Give chemical formula : A) Nickel (III) bromide B) antimony (V) nitride C) platinum (II) phosphide D) lead (II) chloride E) mercury (I) arsenide F) cobalt (II) chloride.