5 7 names formulas of ionic compounds
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5.7 NAMES & FORMULAS OF IONIC COMPOUNDS. The International Union of Pure & Applied Chemistry (IUPAC). Decides on a common naming system known by scientists across the world Recall—Ionic Compounds:2 elements; a metal & a non-metal Therefore their names have 2 parts

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5 7 names formulas of ionic compounds

5.7 NAMES & FORMULASOF IONIC COMPOUNDS


The international union of pure applied chemistry iupac
The International Union of Pure & Applied Chemistry (IUPAC)

  • Decides on a common naming system known by scientists across the world

  • Recall—Ionic Compounds:2 elements; a metal & a non-metal

  • Therefore their names have 2 parts

    first part metal ion

    second part non-metal ion

  • The first part of the name is the same as the name of the neutral metal atom

  • The second part of the name changes the non-metal ending to “ide”


Examples
Examples

  • magnesium + chlorine = magnesium chloride

    (metal) (non-metal) (ionic compound)

  • aluminum + oxygen = aluminum oxide

    (metal) (non-metal) (ionic compound)


Writing these chemical formulas
Writing these chemical formulas.

  • Remember… electrons move from metal atoms to non-metal atoms

  • The charged ions attract other ions of the opposite charge until the charges balance out (positive + negative = zero)

  • The compound that forms is electrically neutral

    ***# of positive charges = # of negative charges***


Chemical formula of magnesium chloride
Chemical Formula of Magnesium Chloride

  • 1 Write the symbols of the elements, with the metal on the left and the non-metal on the right

    Mg Cl

  • 2 Add the ionic charge of each ion above the symbol

    +2 -1

    Mg Cl

  • 3 Determine how many ions of each are required to bring the total charge to zero.

    1 (+2) + 2(-1) = 0

    Mg Cl


Magnesium chloride continued
Magnesium Chloride Continued…

  • 4 Write the chemical formula using the coefficients in front of each as the subscripts

    MgCl2 magnesium chloride

    ***Do not write the subscript “1” in chemical formulas because the symbol itself represents one ion ***


Criss cross rule an easier way to write chemical formulas
CRISS CROSS RULE(An easier way to write chemical formulas)

Ex: Magnesium Chloride +2 -1

  • 1 Write the symbols for each element Mg Cl

  • 2 Write the ionic charge above each symbol

    (the # e- gained/lost to become an ion)

  • 3 Drop the +/- sign

  • 4 Criss cross the numbers of the ionic charges

  • 5 Write the numbers as subscripts : MgCl2

  • 6 Do not write a 1 as a subscript as the 1 is already assumed


Sometimes
Sometimes………

  • Occasionally you get an answer with two identical subscripts

  • Ex: Al3N3

  • Write the compound with subscripts in lowest terms

  • Ex: AlN


This is what it all means
This is what it all means!

MgCl2

There is one atom of magnesium in the molecule

There are two atoms of chlorine in the molecule

Magnesium has two electrons to give away. Chlorine only needs 1 electron. There fore two chlorines are needed to take the two available electrons from magnesium.


Elements with multiple charges
Elements with Multiple Charges

  • Some elements have two stable cations.

    e.g. Fe2+ and Fe3+

  • Fe2+ is called Iron (II) and Fe3+ is called Iron (III)

  • There are two different compounds of iron and chlorine

    FeCl2 (light green solid) and FeCl3 ( yellow-brown solid)

  • Named the same way, except insert rounded brackets with Roman numerals indicating the ionic charge



Naming these compounds
Naming these Compounds

  • Whenever you name a compound containing a metal, ALWAYS check to see if the metal has more than one ionic charge.

  • metal( Roman Numeral) Non metal (with “ide”)

  • If it does, use reverse criss cross to determine the correct “bracket”

    3+ 1-

    FeCl3

  • Double check that the non metal has the correct ionic charge as well

  • If so then it is Fe3+ and the compounds name is iron (III) chloride


Another example fep
Another Example FeP

1 1

FeP

But iron’s valence is 2 or 3 and phosphorous’ valence is 3,5 or 4. Therefore the common valence is 3.

3+ 3-

FeP

Iron (III) Phosphide


Homework
Homework

  • Two Handouts

  • Textbook: pg 200 # 2-5, 7, 9


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