Understanding the differences and relationships of Atoms, Elements, Molecules, and Compounds

1. Understanding the differences and relationships of Atoms, Elements, Molecules, and Compounds http://education.jlab.org/qa/atoms_and_elements.html

2. What are atoms? • Atoms are the smallest bits of ordinary matter and are made from particles called protons (which carry a positive electrical charge), neutrons (which carry no electrical charge) and electrons (which carry a negative electrical charge). • The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons 'orbit' the nucleus. • A particular atom will have the same number of protons and electrons and most atoms have at least as many neutrons as protons.

5. What are Isotopes? • If you had very, very good eyes and could look at the atoms in a sample of hydrogen, you would notice that most of the atoms have no neutrons, some of them have one neutron and a few of them have two neutrons. These different versions of hydrogen are called isotopes. • All isotopes of a particular element have the same number of protons, but can have different numbers of neutrons. If you change the number of protons an atom has, you change the type of element it is. If you change the number of neutrons an atom has, you make an isotope of that element.

6. What is an element? • An element is a substance that is made entirely from one type of atom. • For example, the element hydrogen is made from atoms containing just one proton and one electron. • All known elements are arranged on a chart called the Periodic Table of Elements.

7. What is a compound? • A compound is a substance made from two or more different elements that have been chemically joined. • Some examples of compounds are water (H2O), table salt (NaCl), table sugar (C12H22O11) and chalk (CaCO3).

8. What is a mixture? • A mixture is a substance made by combining two or more different materials in such a way that no chemical reaction occurs. • A mixture can usually be separated back into its original components. • Some examples of mixtures are a tossed salad, salt water and a mixed bag of M&M's candy.

9. What is the difference between a compound and a molecule? • A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements. All compounds are molecules but not all molecules are compounds. • Molecular hydrogen (H2), molecular oxygen (O2) and molecular nitrogen (N2) are not compounds because each is composed of a single element. • Water (H2O), carbon dioxide (CO2) and methane (CH4) are compounds because each is made from more than one element. • The smallest bit of each of these substances would be referred to as a molecule. For example, a single molecule of molecular hydrogen is made from two atoms of hydrogen while a single molecule of water is made from two atoms of hydrogen and one atom of oxygen.

10. More on molecules and compounds… • A molecule is what you get when any atoms join together. • A compound is what you get when atoms of two or more different elements join together. • All compounds are molecules, but not all molecules are compounds. • Water is a molecule because it is made from atoms that have been chemically combined. It is also a compound because the atoms that make water are not all the same - some are oxygen and some are hydrogen. • Oxygen in the atmosphere is a molecule because it is made from two atoms of oxygen. It is not a compound because it is made from atoms of only one element - oxygen. This type of molecule is called a diatomic molecule, a molecule made from two atoms of the same type.

11. Imagine going to an ice cream store. Let's say that they have 30 different flavors of ice cream. Those are elements, the things that I have available to build my dessert from. The smallest amount of ice cream that the store will sell to me is a scoop. This is an atom. If I want, I can put two or more scoops of ice cream together. This is a molecule. If my molecule has more than one flavor of ice cream, I can call it a compound. • element - a basic substance that can't be simplified (hydrogen, oxygen, gold, etc...) • atom - the smallest amount of an element • molecule - two or more atoms that are chemically joined together (H2, O2, H2O, etc...) • compound - a molecule that contains more than one element (H2O, C6H12O6, etc...) • What's wrong with the ice cream analogy? Splitting an atom creates different elements (split an oxygen atom and you don't have oxygen any longer). Splitting a scoop of ice cream results in smaller blobs of the same flavor. For the analogy to hold true, the flavor of the ice cream would have to change when you split a scoop (the chocolate 'element' would have to change into some other 'element' (flavor)).

12. Carbon (C) • The Element Carbon6 • C • Carbon • 12.0107 • Atomic Number: 6 • Atomic Weight: 12.0107 • Melting Point: 3823 K (3550°C or 6422°F) • Boiling Point: 4098 K (3825°C or 6917°F) • Density: 2.2670 grams per cubic centimeter • Phase at Room Temperature: Solid • Element Classification: Non-metal • Period Number: 2    Group Number: 14    Group Name: none • What's in a name? From the Latin word for charcoal, carbo. • Say what? Carbon is pronounced as KAR-ben. • Carbon, the sixth most abundant element in the universe, has been known since ancient times. Carbon is most commonly obtained from coal deposits, although it usually must be Estimated Crustal Abundance: 2.00×102 milligrams per kilogram • Number of Stable Isotopes: 2   (View all isotope data)