Environmental Chemistry
Unit 1 Sections B-1 through B-11 Study Guide
B.1 Grouping The Elements
1. periodic table – chart that organizes the elements.
2. Dimitri Mendeleev – Russian chemist who published a periodic table in 1869.
B.2 Early Periodic Tables
1. early periodic tables of the 1800’s were organized according to
a. physical characteristics of elements - mass
b. chemical characteristics of elements – “combining capacity” with other elements.
2. Early periodic tables organization
a. vertical columns (now called Groups or Families) were organized with elements of similar chemical
properties.
b. horizontal columns (now called periods) were organized based on increasing atomic masses.
We now know that elements listed in the rightmost column are unreactive (noble) gases.
B.3 The Electrical Nature of Matter
1. Like charges repel
2. Unlike charges attract
3. Electrically neutral (uncharged) atoms contains equal number of positively charged particles called protons and
negatively charged particles called electrons. Most atoms contain one or more electrically neutral particles called
neutrons.
B.4 The Modern Periodic Table
1. The modern periodic table is placed in sequence by atomic number – number of protons (also number of electrons
in neutral (uncharged) atoms.
2. The nucleus is a concentrated region of positive charge (due to protons) in the center of an atom.
3. The mass number is the total number of protons and neutrons in the nucleus of an atom.
4. Isotopes are atoms with the same number of protons but a different number of neurtrons. (We will discuss isotopes
later, this is not on the test!)
B.5 Counting Subatomic Particles
Neutral atom – Number of protons and electrons are equal
Cation – positively charged atom – more protons than electrons
Anion – negatively charged atom - more electrons than protons
B.6 Periodic Variation in Properties
Graphing guidelines
-
Title
X-axis – independent variable
Y- axis – dependent variable
Scale - Determine the range of your data and divide by the number of lines that you would like to use on your
paper.
Trends in a chemical property
-
Oxidation numbers decrease from left to right on periodic table
Trends in a physical property
-
Boiling point increases as you down the groups (or columns) on the periodic table. If you know the boiling point
of an element on top and below an element with an unknown boiling point than you take the average of the
known boiling points to find the unknown boiling point.
B.7 Organization of the Periodic Table
Periods – rows on the periodic table
Group or Family – columns on the periodic table.
Alkali metal family – consist of the six elements (starting with lithium) in the first column at the left of the periodic
table. Each is a highly reactive metal.
Noble Gas family – consist of very unreactive (or chemically inert) elements located at the right of the periodic table.
Halogen family – are highly reactive and readily form binary compounds with hydrogen. This group is found just to the
left of the noble gases – fluorine, chlorine bromine and iodine.
B.8 Predicting Properties
Periodic properties – vary among elements according to trends that repeat as atomic number increases.
Example 1 : Estimate the melting point of rubidium (Rb). The melting points of potassium (K) and cesuium (Cs) are 337K
and 302 K, respectively.
Answer: Since K is above RB and Cs is below Rb on the periodic table we would average the two numbers – (337 +
302)/2 = 639/2 = 319.5 K
Example 2 Here are formulas for several Known compounds: NaI, MgCl2, CaO, Al2O3 and CCl4.
First write the group of each element on top of the formula. Than match these groups with the elements given.
Using that information, predict the formula for a compound formed from:
a. C and F - Since C and C are the same element; F and CL are in Group 17 CF4
b. Al and S – Since Al and Al are the same element; S and O are in Group 16 Al2S3
c. K and Cl - Since K and Na are in Group I; I and Cl are in Group 17 KCl
d. Ca and Br – Since Ca and MG are in Group 2 and Br and Cl are in Group 17 CaBr2
B.9 Periodic Trends
Discusses the halogen group – skip we did not do the experiment.
B.10 Ions and Ionic Compounds
Ionic compounds are substances that are composed of positive and negative ions, which are electrically charged atoms
or groups of atoms.
Neutral atom – Number of protons and electrons are equal
Cation – positively charged atom – more protons than electrons
Anion – negatively charged atom - more electrons than protons
Ion Formation in Representative Elements
Group Gain or Lose
Charge of Ion
1 (1A)
lose 1
+1
2 (2A)
lose 2
+2
13 (3A)
lose 3
+3
14 (4A)
lose or gain 4*
15 (5A)
gain 3
-3
16 (6A)
gain 2
-2
17 (7A)
gain 1
-1
+4,-4*
Remember when we gain electrons our ion becomes negative (by the amount of electrons we lose).
When we lose electrons our ion becomes positive (by the amount of electrons we gain).
See worksheets involving calculating charges of various ions. We are always looking out how
Examples of figuring out the charge of an ion:
Sodium (NA) Ion: 11 protons (11+ charge)
+ 10 electrons (10- charge) (there are 10 electrons because Na loses one electron in
it’s outer shell)
Sodium Ion (1+ charge) thus Na+