COMPOSITION OF POLLUTION - FREE GROUND LEVEL AIR

Nitrogen	78.08%
Oxygen	20.95%
Carbon Dioxide	0.03%

 

COMPOSITION OF UNIVERSE		COMPOSITION OF EARTH
Hydrogen	60.40%		Iron	35.4%
Helium	36.56%		Oxygen	27.8%
Oxygen	0.96%		Magnesium	17.0%
Carbon	0.30%		Silicon	12.6%

 

ELEMENTS

90 Naturally occurring
19 Synthesized
109 TOTAL

ATOM Chapter 2

What is it?

Def: The smallest particle still having the characteristics of an element.
        It is made up of smaller particles: electrons, protons, and neutrons.

Simplest atom is H (hydrogen).

 

electron

proton

 

PROTON

1. Positive charge
2. "Weighs" 1 amu (atomic mass unit)
     1 lb. = 273 x 10²⁴ amu
3. The number of protons is the atomic number of an element.
4. The number of protons tells you what the element is.
5.  What element has 6 protons?
6.  How many protons in the element nitrogen (N)?

ELECTRON
1. Negative charge
2. 1835 electrons weigh 1 amu.
3. Responsible for chemical bonds

NEUTRON
1. No net charge
2. Weighs 1 amu

ATOMIC WEIGHTS

To get the atomic weight you add the number of protons and neutrons. When the protons and neutrons are considered as a unit, they are referred to as "nucleons".

Def. Average weight of all the atoms of an element.

Hydrogen has 1 proton and 1 electron, totaling 1 amu.

Deuterium has 1 proton (1 amu), 1 neutron (1 amu),
               and 1 electron, totaling 2 amu.

Tritium has 1 proton (1 amu), 2 neutrons (2 amu), and 1 electron, totaling 3 amu.

ISOTOPES

Def: Atoms of the same element that have the same
       atomic number but have different mass numbers.

       The isotopes of an element all have the same number of protons but a different number of neutrons.

       Hydrogen, deuterium and tritium are isotopes.

       Tritium is radioactive.

ISOTOPES OF URANIUM

238                   235
    U             U
 92                    92

What does the 92 mean? What does the 238 mean?

Summary:

Atomic number
Atomic weights

ISOTOPES

A
  X             X = symbol of the element
Z                      Z = number of protons
                        A = mass number (number of protons and neutrons)

                    ¹H = hydrogen      ²H = deuterium        ³H = tritium
                    ^{1                                    1                                       1}

ATOMIC STRUCTURE

2 electrons can fit on the first level

 

 

8 electrons on the second

Atoms are happy when a shell or level is complete - will enter into reaction just to get the number of electrons for that shell.

 

IONS

When an atom does not have the same number of electrons and protons, it has a charge. This is an ion.

If an ion had 11 protons and 10 electrons, it would be a positive ion. These are called cations.

What element has 11 protons?

If an ion had 17 protons and 18 electrons, it would be a negative ion. These are called anions.

What element has 17 protons?

Atoms and Ions

Atoms have no net charge. They are neutral.

Ions have a charge, either positive or negative.

A positive ion has more protons than electrons. CATION

A negative ion has more electrons than protons. ANION

The ion of an atom has very different chemical properties than the atom or molecule. Sodium is a soft metal, which reacts with water and gives explosive hydrogen.

The sodium ion is half of table salt NaCl, which dissolves in water and is needed for human life.

                                        23Na                 ²³Na⁺

# protons     

# neutrons

# electrons

 

Problems

Chemical Symbol	#Protons	# Neutrons	#Electrons	Charge	Name
4020Ca++
19078Pt
22387Fr
12953I-
4He
		7	6		Carbon
		14	15		0
		18	18		Sulfur ion
		30	24		Iron ion
		118		+3	Gold ion
	9	9		-1

Problems at end of Chapter 2

2.16 ; 2.17; 2.21; 2.26; 2.28

 

PERIODIC CHART Pages 37 - 40

 

Lithium 
                        Neon

 

Sodium 
                        Argon

 

Potassium

 

 

(More electrons could have fit on the 3rd level - 18 - but that electron goes to the 4th level instead- will cover later.)

Group 1A Called alkali metals. All have 1 electron on the
outermost shell. Will enter same type of reactions. This
group will give up that electron to some other element.

Li                                 Li⁺ ion

 

Na                               Na⁺ ion

Group VIII Noble gases - happy with their electonic structure
they don't react, they are inert.

Group II All have 2 electrons on outer shell.

Be                             Be⁺⁺ ion

 

Mg                            Mg⁺⁺ ion

 

Ca                             Ca⁺⁺ ion

 

Group VII             7 electrons on outer shell - Halogen family

F                                 F + 1e^-     F^- ion

 

Cl                               Cl + 1 e^-   Cl^- ion

 

Group III             B 3 electrons
                           Al

Group IV           C 4 electrons
                          Si

Group V            N 5 electrons
                          P

Group VI          O 6 electrons
                         S

ENERGY SHELLS OR ENERGY LEVELS

nucleus                 n = 1                 n = 2             n = 3             n = 4
Electrons are on energy levels or shells. These shells can have subshells or sub levels.

Energy level 1 has only 1 subshell                 holding 2 electrons
Energy level 2 has 2 subshells                       holding 8 electrons
Energy level 3 has 3 subshells                       holding 18 electrons
Energy level 4 has 4 subshells                       holding 32 electrons

Wednesday, March 21, 2007 01:28:01 PM