Elements+and+Atoms



** Table of Contents **

1. Elements, Compounds and Mixtures 2. Particles of Elements
 * Building Blocks Of Matter**

1. The Modern Atomic Model 2. Dalton's Atomic Theory 3. Rutherford and the Nucleus 4. Interesting Facts
 * Atomic Theory and Models**


 * Works Cited**

**Building Blocks Of Matter**

Elements, Compounds And Mixtures

A Compound is a combination of elements which have been chemically combined. Compounds always have the same exact combination of elements, with the same exact ratio. A common example is table salt, or sodium chloride. The exact mixture is 39.3% sodium and 60.7% chlorine, as determined by the mass of the compound. A mixture, on the other hand, is made of two or more elements which are in the same place, yet are not chemically combined. A very common mixture is the air we breathe. It is a combination of mainly nitrogen and oxygen. There are also many small elements and compounds which together make up about 1% of the air, including argon and carbon dioxide. When new elements are discovered, they must be identified as a new element by the IUPAC (International Union of Pure and Applied Chemistry). Usually, when a new element is discovered, it is named after the discoverer. Particles of Elements

Elements are the simplest forms of matter, but they are not the smallest. The smallest particle of am element is called an atom. Atoms are the smallest possible pieces of matter and cannot be cut in half. The idea of the atom was created from the thought of whether everything could always be cut in half, or if it would eventually become uncuttable. The idea of the atom was originally introduced by the ancient Greek philosopher Democritus. His theory of atoms wasn't widely accepted until over 2000 years later. The term he used was //**Atomos,**// which means "Uncuttable" in Greek. In 1911, Ernest Rutherford discovered that the atom had a nucleus, a large collection of an atoms positive particles, called protons, which is always located in the center of the nucleus. In 1913, Niel Bohr suggested that the negative particles in an atom, the electrons, circle the nucleus in a fixed orbit. Since all atoms have a neutral charge (If the charge isn't neutral, it is considered an ion), the number of positive particles and negative particles are always equal. In the 1920's, the principle of uncertainty was introduced. This theory says that it is impossible to know the exact position and momentum of a sub-atomic particle. The mass of an atom is determined by mostly the amount of protons and neutrons, but there is a small amount of mass, a very small amount, which comes from the electrons. The official equation is:

** Atomic Theory and Models **
 * 1) # of Protons + # of Neutrons + (# of electrons X 0.00055). This means that you add the number of protons and neutrons, since their masses both equal one Atomic Mass Unit (AMU), and then you take the number of electrons and add 55/100000 of that number.

Modern Atomic Model The Modern Atomic Model was discovered by British scientist James Chadwick in 1932. He realized that atoms had more mass than it seemed if you counted only the electrons and protons. He looked at atoms and found that there was that there was a third particle in an element, one with the same mass as a proton yet that has a neutral charge. He called this particle the Neutron. This particle was difficult to find, since it had no charge and had the same mass as a proton. A video describing the different particles in an atom, and the difference between an atom and an ion, can be found below.

media type="custom" key="6209219"

"Isotopes of Hydrogen, Helium, Lithium, and Sodium." //Nerdvana.org//. Web. 17 May 2010. . Dalton's Atomic Theory

John Dalton was the first scientist to create an actual model of an atom, and he created a set of rules that all atoms follow. The rules are as follows: 1. All elements are made of atoms which cannot be divided. 2. All atoms of the same element are exactly the same, and atoms of different elements are all different from eachother. 3. Atoms of one element cannot be changed into atoms of other elements. Atoms also cannot be created or destroyed, only rearranged.' 4. Every compound is composed of atoms of different elements, combined in a specific ratio. These rules are still followed today, and Dalton's model is still used, with only minor changes having been made in the 200 years since then.

Rutherford and the Nucleus Ernest Rutherford was a student if British scientist J.J. Thomson, who discovered the smaller charged particles in an atom, the proton and the electron. Rutherford disproved Thomson's model of an​ atom, which consisted of a positively charged sphere which was embedded with the negative particles. Rutherford's model had all of the positive particles clumped in the middle, in what is called the nucleus, with the negative particles flying around it in random paths. He proved his theory by shooting particles at a sheet of gold foil. He observed that most of the particles passed through, but a few were reflected off of the foil. Rutherford reasoned that these particles were reflected because of relatively large masses in the middle of the atoms, which he named the nucleus. He also reasoned that they must be the positive particles, since the negative particles, the electrons, had almost no mass. Rutherford named these positive particles "Protons", which is how we refer to them today. Below is a diagram depicting Rutherford's experiment, which helped him discover the nucleus.



Interesting Facts > Works Cited > > Padilla, Michael. //Chemical Interactions//. Upper Saddle River, NJ: Pearson, 2009. 6-11. Print. > > "Element, Chemical." //UXL Encyclopedia of Science//. 4. 1998. Print.
 * A cloud of electrons surround a nucleus in an atom, and each electron flies a random path around the nucleus.
 * Atoms were originally considered to be a single piece of matter, with no smaller particles existing. Today, however, we know that an atom is made up of smaller particles with different electrical charges, called Protons (Positive Charge), Electrons (Negative Charge), and Neutrons (Neutral/No Charge). Atoms still have been proven to be uncuttable, though.
 * The actual size of an atom can be up to a 100,000 times the size of the nucleus. that means that if you had a nucleus the size of a dime, you could see electrons that are miles away, still flying around the nucleus.

"Atom." //International Encyclopedia of Science and Technology//. 1998. Print.

"Element, Chemical." //World Book E-6//. 2007. Print.

"Atoms ." //UXL Encyclopedia of Science//. 1998. Print.