Intro to Chemistry What are the molecules on the left of the - PDF document

8/29/2018 Central Questions • Where can you find the chemical symbols for the different elements? Intro to Chemistry • What are the molecules on the left of the equation called? What about on the right? Atoms Element Example • All particles of matter are made of atoms. Atomic # • Atoms are made of: What is the number of protons? 8 o Protons + O o Neutrons-neutral What is the number of neutrons? o Electrons – Oxygen • Protons and electrons are the same number unless it has a charge What is the number of electrons? • Element: pure substance of only one kind of atom (ex. Gold). 118 are 15.999 found on the periodic table. • Atomic Number: # of protons • Atomic Mass: protons + neutrons Atomic Mass Bond Types Chemical Formula • Compound — substance made of 2 or more atoms • Chemical formulas show the elements and joined together by a chemical bond number of atoms of each element in a molecule • Covalent bond — share electrons, strongest • H 2 SO 4 Subscript • Ionic bonds — electrons are gained or lost; break Elements down in water (salt) Hydrogen: 2 atoms • Hydrogen bonds — attraction between partial Sulfur: 1 atom positive and partial negative charges; common in Oxygen: 4 atoms water 7 atoms total 1

8/29/2018 Coefficients Coefficients • 2H 2 SO 4 — 2 molecules of Sulfuric Acid • A formula may begin with a number called a coefficient. It represents the # of molecules of that compound or atom -A coefficient is distributed to ALL elements in a need in the reaction. compound -For example: • 2 — H 2 (for a total of 4 H atoms) • 2H 2 SO 4 — 2 molecules of Sulfuric Acid • 2 — S (for a total of 2 S atoms) • 2 — O 4 (for a total of 8 O atoms) Reading Chemical Equations Reading Chemical Equations • Each side of an equation represents a combination of • The two sides of the equation are separated by an chemicals. arrow. • The combination is written as a set of chemical -The combination of chemicals before the reaction formulas, separated by + symbols. are on the left side of the arrow. These are the reactants. -The right side indicates the combination of CH 4 + 2O 2  CO 2 + 2H 2 O chemicals after the reaction. These are the products. Coefficient For Example: Balancing Equations REACTANTS  PRODUCTS • The Law of Conservation of Mass states that in a chemical reaction, the quantity or amount of each element does not change. Na + O 2  Na 2 O • This means that each side of the equation must represent the same quantity of each element; in other words have the same number of each kind of atom. • The reactants are Na and O2 • The products are Na2O 2

8/29/2018 Balancing Equations Balancing Equations Na + O 2  Na 2 O 2Na + O 2  Na 2 O • There are 2 Na’s on the left and 2 Na’s on the right. But • In order for this equation to be balanced, there what about the O? must be equal amount of Na on the left hand • We now must check to see if the O’s are balanced on both side and on the right hand side. sides of the equation. On the left hand side, there are 2 O’s • Right now, there is 1 Na atom on the left but 2 and the right hand side only has one. This is still an Na atoms on the right. We solve this problem by unbalanced equation. To fix this, we must put a 2 in front of the Na 2 O on the right hand side. Now our equation putting a 2 in front of the Na on the left hand reads: side, like this: 2Na + O 2  2Na 2 O 2Na + O 2  Na 2 O Is this equation balanced now? Central Questions • Where can you find the chemical symbols for the different elements? • What are the molecules on the left of the equation called? What about on the right? 3