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Activity 16 Name___________________________________Per______ Elements and the Periodic Table Atoms are extremely small particles that make up absolutely everything. Atoms are made up of three main parts. The positively charged protons and the neutrons that have no charge are found in the nucleus of the atom, while the negatively charged electrons orbit around the outside of the atom’s nucleus. Not surprisingly, it is these electrons (on the outside) that are involved in the chemical reactions that occur between elements. What are elements? _______________________________________________________________________________ How do elements relate to compounds? _____________________________________________________________ __________________________________________________________________________________________________ Each element has a one or two letter symbol. Each symbol must be unique. There are 115 different elements. We have only 26 letters in the English language. You can see why some require more than one letter. The symbols of many elements come from Latin and Greek languages (for example Iron is symbolized Fe because of its Latin name ferrous. Put either the symbol or the name of the element in each blank below. _____ Carbon Na _____________ _____ Aluminum _____ Gold O _____________ _____ Nitrogen Ne ___________ H ______________ Each element has a specific atomic number that reveals the number of protons that its atoms contain. Use the Periodic Table to determine how many protons are found in the atoms of the following elements. _____ Lithium _____ Beryllium _____ Boron _____ Carbon Do you see another of the patterns that Mendeleev and other scientists recognized? ___________ Neutral atoms contain equal numbers of protons (+) and electrons (-). Because of this, you know that neutral atoms of lithium, beryllium, boron and carbon also have 3, 4, 5, and 6 electrons respectively. When two elements are near one another they often react. Much like reactions between two people, elements may attract one another and “bond” or move apart and never connect. Remember that chemical reactions involve the electrons. Electrons come and go and change the charge of the element. Some elements have all the electrons that they “need” and therefore are not “interested in” reacting. These elements are not reactive; often thought to be distant, unfriendly, or standoffish. Consequently, this group is named the “noble gases.” Name three elements that are highly reactive. ________________________________________________________ Name three elements that are not reactive. ___________________________________________________________ The majority of the 115 elements are reactive. They tend to combine with other elements to form compounds. We can even predict which elements will react and what other elements by using the Periodic Table of Elements. For example, elements in column 1 tend to react with elements in column 17, elements in column 2 tend to form compounds with elements in column 16. Your teacher will explain why this is so. Take some notes on the back of this sheet to help you remember this concept. Compounds are always neutral. Often times, the ratio of atoms in the compound is NOT one-to-one. The subscripts in the chemical formula reveals important information. What is the ratio of hydrogen to oxygen atoms in a water molecule? ______ to ______ Analysis 1. Use the periodic Table of Elements to find out which atoms make up a molecule for each of the substances listed. The first row has been done for you. Substance Chemical Formula Water H2O Hydrogen Peroxide H2O2 Carbon Dioxide CO2 Sucrose (Table Sugar) C12H22O11 Alanine (an amino acid) C3H7O2N Oleic Acid (a fat) C12H24O2 Atoms that Make up the Molecule 2 hydrogen atoms 1 oxygen atom 2. Sodium is a metallic solid, and chlorine is a poisonous, yellow-green gas. Sodium and chlorine react to form sodium chloride, which is common table salt. a. Is table salt an element or compound? Explain. b. Describe the physical properties of table salt. c. How do the properties of table salt compare with those of sodium and chlorine?
