Atoms, Elements, & Mixtures Chapter 2.2—2.4 Notes

Atoms are the fundamental components of elements Atoms make up everything around us—your desk, pen, etc. We know of only ~100 different types of atoms—90 are found in nature while the remainder can be made by scientists in the lab An element is any material that is made up of only one type of atom Pure gold, nitrogen, the graphite in your pencil is made of only carbon Elements are listed in a chart called the periodic table

Elements combine to form compounds How many atoms are bound together in an element is shown by an elemental formula Au: Gold; Li: Lithium; N 2 : two Nitrogen atoms bound together Au, Li, and N are the atomic symbols for gold, lithium, and nitrogen, respectively Compounds are formed when atoms of different elements bond to one another

Compounds Chemical formulas represent a compound—symbols for the elements are written together NaCl: sodium chloride—one sodium for every one chloride NH 3 : ammonia—one nitrogen for every three hydrogen The physical and chemical properties of a compound are different from the properties of their elemental components Na—soft, silvery metal that can easily be cut with a knife Cl—yellow-green gas at room temperature, very toxic NaCl (salt)—translucent, brittle, colorless crystal

Naming Compounds The International Union for Pure and Applied Chemistry (IUPAC) has created a system for naming compounds Naming reflects the elements within a compound

Naming Compounds Guideline 1: The name of the element farther to the left in the periodic table is followed by the name of the element farther to the right, with the suffix -ide added to the name of the latter NaCl: Sodium + chlorine = Sodium chloride Li 2 O: Lithium + oxygen = Lithium oxide CaF: Calcium + fluorine = HCl: Hydrogen + chlorine = MgO: Magnesium + oxygen = Sr 3 P 2 : Strontium + phosphate = What does the “2” tell us in Li 2 O? The “3” and “2” in Sr 3 P 2 ?

Naming Compounds Guideline 2: When two or more compounds have different numbers of the same elements, prefixes are added to remove the ambiguity. The first four prefixes are mono- (“one”), di- (“two”), tri- (“three”), and tetra- (“four”). The prefix mono- is commonly omitted from the beginning of the first word of the name. Carbon and oxygen CO: Carbon monoxide CO 2 : Carbon dioxide Nitrogen and oxygen NO 2 : N 2 O 4 : Sulfur and oxygen SO 2 : SO 3 :

Naming Compounds Guideline 3: Some compounds are not referred to by their systematic name and are instead given common names Water: H 2 O Ammonia: NH 3 Methane: CH 4