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Elements and Compounds
Elements are substances that cannot be separated into simpler substances. Salt is made up of the elements sodium and chloride. Water is made up of the elements hydrogen and oxygen. The smallest particles of matter are called atoms. If you continue to chop a carrot into smaller and smaller pieces, eventually you would reach a point where you could not cut up the carrot anymore, but still have carrot. You would then have molecules of carrot. The same applies to elements. If you continually cut up a piece of aluminum, you will reach a point that you could no longer divide it. These are aluminum atoms. An atom is the smallest particle of an element that has the properties of that element. Some properties of aluminum are: shiny, silver colored, fragile, and thin. Each element has its own type of properties. Chemists use chemical symbols to represent elements. A chemical symbol is a letter or picture used to represent something. Chemists use one or two letters to represent elements. The symbol for aluminum is Al. The symbol for oxygen is O.
A model of an oxygen molecule. (02= 2 oxygen atoms)
A pair of oxygen atoms is a molecule of oxygen. A molecule is the smallest particle of a substance that exists independently. Molecules of most elements are made up of only one of atom of that element. Oxygen, along with nitrogen, hydrogen, and chlorine are made up of two atoms. Look at the model of oxygen above. The two balls represents the two oxygen molecule. The oxygen molecule are bonded or stuck together by chemical means.
A compound is a substance formed when two or more elements are chemically joined. Water, salt, and sugar are examples of compounds. When the elements are joined, the atoms lose their individual properties and have different properties from the elements they are composed of. Think of the sodium and chlorine from the video. By itself sodium is highly reactive…explosive even when mixed with water, but when its joined with chlorine it turns into a yummy treat, salt. The same thing is true about hydrogen and oxygen. Alone each is a highly reactive gas that invisible to the naked eye. But when they join chemically by sharing electrons, they form a nice drink, water. By sharing electrons as a compound those elements take on new properties. The example on your left represents the compound Calcium carbonate, we know it in school as chalk. Chemically remove the calcium and one oxygen and we get the gas we breath out, carbon dioxide. Everything around us is made up of elements or a combination of elements called compounds. Decide if it’s an element or a compound. For the compounds write out the chemical formula.
1. ______________ Silicon dioxide (sand) 2. ________________Oxygen
3. ________________ Lead monoxide 4. _______________Carbon dioxide
5. ________________ Fluorine 6. _________________ Bromine
Using your periodic table fill in the missing information!
Names
Atomic
Atomic
Atomic
symbol
number
mass
Protons
Electrons
B
11
31
39
Pb
70
Aluminum
Mo
47
100
Sodium
106