Monday, February 3, 2020

SCH 3U/4C - Nomeclature - Prefix Naming System

Another method of naming compounds in which the first element (usually P, S, C, N, Si) may have more than one valence is called the prefix system.  This method is used only with compounds containing two non-metals. 



Prefixes:                1        mono-
                              2        di-
                              3        tri-
                              4        tetra-
                              5        penta-
                              6        hexa-
                              7        hepta-
                              8        octa-
                              9        nona-
                             10       deca-


Rules for Writing a Name from a Formula
1.     Write down the name as you did for binary compounds.

2.    Include a prefix with the first element name that indicates how many of the first atom are present.  However, if there is only one atom in the first position, do not use the mono- prefix.

3.    Include a prefix with the second element name that indicates how many of the second atom are present.

ex. (a)  CO         carbon monoxide
      (b)  N2O       dinitrogen monoxide
      (c)  SCl3       sulfur trichloride
              



Rules for Writing a Formula from a Name


1.  Just write what the name tells you.

ex.(a)  dinitrogen tetroxide            N2O4
     (b)  sulfur hexafluoride             SF6
     (c)  diphosphorus pentoxide     P2O5


Can't have too much prefix in your life?  Check out this video.


Homework

Give the correct formula for the following.
1.     sulfur trioxide
2.    carbon monoxide
3.    phosphorus triiodide
4.    silicon tetrafluoride
5.    sulfur dioxide
6.    diphosphorus pentoxide
7.    carbon tetraiodide
8.    diphosphorus pentasulfide
9.    sulfur hexabromide
10.  silicon disulfide

Give the correct name for the following.
1.     CO2
2.    CO
3.    CS2
4.    SO2
5.    P2O3
6.    CCl4
7.    PCl3
8.    SiO2
9.    P2O5
10.  SCl6
 
Answer Keys: