CHEMISTRY - NUCLEAR MODEL OF THE ATOM MODULE #2 C

What is the nuclear model of the atom?

The model states that the atom consists of a dense positive center called the nucleus and is orbited by negatively charged electrons.
The nuclear model of the atom was first proposed by New Zealand scientist Ernest Rutherford while working in England under J. J. Thomson.
Scientists have shown that the atom consists of three sub atomic particles, the proton, the neutron and the electron.

• The center of an atom is called the nucleus. It contains most of the mass of an atom. Over 99.9% of the mass of an atom is found in its nucleus.
• The nucleus is composed of postively charged protons and neutrons which are neutral in charge.
• Negatively charged electrons orbit the nucleus at a great distance compared to the size of the nucleus.
• Most of the atom is consists of empty space.

Each sub atomic particle has its own unique characteristics and properties as shown by the table below.

Sub atomic particle	Found	Charge	Relative mass	Function or role
Proton	In the nucleus	Positive (+)	1800	Determines the identity of an element. Each element has an unique number of protons called the Atomic Number.
Neutron	In the nucleus	Neutral (0)	1801	Helps stabilize the nucleus
Electron	Orbiting the nucleus	Negative (-)	1	Outer electrons involved in chemical reactions

The nuclear model of the atom describes the atom as consisting of a positively charge dense nucleus made up of protons and neutrons. Negatively charged electrons orbit the nucleus at a great distance from the nucleus Most of the atom is made up of empty space.
In an neutral atom the number of positively charged protons is equal to the number of negatively charged electrons. 

An atom of carbon has 6 protons and 6 electrons. An atom of bromine has 35 protons and 35 electrons.

CHEMISTRY - NUCLEUS MODULE #2A

NEUTRONS

Neither Here nor There

Neutrons are the particles in an atom that have aneutral charge. They aren't positive like protons. They aren't negative like electrons. But don't start thinking that they aren't important. Every piece of an atom has huge importance to the way the atom acts and behaves. Neutrons are no exception. 

So, if an atom has equal numbers of electrons and protons, the charges cancel each other out and the atom has a neutral charge. You could add a thousand neutrons into the mix and the charge would not change. However, if you add a thousand neutrons, you will be creating one super-radioactive atom. Neutrons play a major role in the mass and radioactive properties of atoms. You may have read the page on isotopes. 

Isotopes are created when you change the normal number of neutrons in an atom. 

Inside the Nucleus

You know that neutrons are found in the nucleus of an atom. Under normal conditions, protons and neutrons stick together in the nucleus. During radioactive decay, they may be knocked out of there. 

Neutron numbers are able to change the mass of atoms, because they weigh about as much as a proton and electron together. If there are many atoms of an element that are isotopes, the average atomic mass for that element will change. We have spoken about carbon (C) having an average mass of 12.01. It's not much different than you would expect from an atom with 6 protons and 6 neutrons. The number of carbon isotopes doesn't change the atomic mass very much. As you move higher in the periodic table, you will find elements with many more isotopes. 

One Special Element

Did we say that all atoms have neutrons? Oops. All elements have atoms with neutrons except for one. A normal hydrogen (H) atom does not have any neutrons in its tiny nucleus. That tiny little atom (the tiniest of all) has only one electron and one proton. You can take away the electron and make an ion, but you can't take away any neutrons. Hydrogen's special structure becomes very important when you learn how hydrogen interacts with other elements in the periodic table. If you learn about nuclear fusion you will learn about deuterium and tritium.

Deuterium is a hydrogen atom with an extra neutron and tritium has two extra. You won't find much deuterium in your backyard. It's mainly in oceans. Don't worry if you do find it, it's not radioactive. It's a stable isotope.

CHEMISTRY - ELEMENT OF THE DAY - CADMIUM

Element of the Day: Cadmium

Great for batteries, bad for kidneys. That’s Cadmium. Cadmium is a soft, slightly bluish metal. What most people don’t know is that it is named after a greek mythological character named Cadmus. Cadmus was apparently a pretty intelligent guy; Myth states that he introduced the Phoenician letters to the Greeks. Why was cadmium named after Cadmus? No idea. However, if you’re ever on Jeopardy you now know the question to some answer. It’s a little more odd that it was named after a greek mythological character since it was discovered by two guys in Germany in the 1800s.

Cadmium is a metal that most people know due to its use in Nickel-Cadmium batteries. However, cadmium is also used as a pigment for red, orange, and yellow, it is used to coat metals prone to corrosion, and as a stabilizer in old-school PVC. A small amount of cadmium is used in nuclear reactors to control the rate of fission. Unfortunately, that’s about as exciting as it gets for cadmium’s uses.

Cadmium is rarely used in pigments or as coatings now because of negative environmental and health effects. If you’re a smoker you have a cadmium blood-level that is about 4-5 times higher than an average American. Is it an issue? Possibly. High cadmiun levels can cause renal issues although if you’re healthy in most other ways and have average iron levels you’re probably all right.

That’s about it for cadmium. As long as you stay away from eating batteries and don’t lick old yellow train cars you probably won’t come in direct contact with it.

CHEMISTRY - MOLECULES MODULE #2 B

Molecules can be divided into two groups

• Molecules of elements
• Molecules of compounds

Molecules of elements	Molecules of compounds
Hydrogen, H2 Oxygen, O2 Nitrogen. N2 Fluorine, F2 Chlorine, Cl2 Bromine, Br2 Sulfur, S8	Water, H2O Carbon dioxide, CO2 Hydrogen sulfide, H2S Sulfur dioxide, SO2 Ammonia, NH3 Methane, CH4 Methyl alcohol, CH3OH

Molecules of elements are made up of the same type of atoms
The hydrogen molecule is made up of two atoms of hydrogen and has the chemical formula of H₂

Hydrogen, H₂

Molecules of compounds are made up the at two or more different atoms.

Water, H₂O

The water molecule is made up of atom of oxygen and two atoms of hydrogen. It has the chemical formula of H₂O.


REVIEW: 

A molecule is the smallest part of a substance called a compound that still is that substance. 

• For example, a molecule of water is the smallest bit of water that still is water. A molecule of a substance cannot be seen by the naked eye - a drop of water is made up of many, many molecules of water.

• Molecules are composed of atoms joined together chemically. 
• Molecules do not have an electrical charge.  
• Scientists believe that molecules are always moving. 
• They can be solids, liquids or gases. 
• Molecules move the most and are the furthest apart when they are gases. 
• Molecules are closest together and move the most slowly when they are solids. 
• Molecules that are liquids movement is between those of gases and those of solids.

A formula tells what elements make up a molecule. 

• For example, a molecule of water is made up of two hydrogen atoms and one oxygen atom. The formula for a molecule of water is H2O.

Molecules come in different sizes and molecular weights. 

• Their atoms can be arranged in different ways. 
• Molecules in substances can be split up in chemical reactions to form other molecules. 
• They can also recombine into larger molecules or be broken down into smaller molecules,