PRACTICE PACKET Basic Chemistry

Transcription

1 Honors Biology Name KEY PRACTICE PACKET Basic Chemistry

2 #1 Periodic Table Use the following terms to fill in the blanks for questions 1-8: protons mass number neutrons energy levels nucleus symbol electrons atomic number 1) The periodic table is arranged in general order of increasing a) atomic number, b) atomic mass and, c) energy levels. 2) Each element in the table has a different a) _atomic number, b) symbol, c) atomic mass, and d) # protons. 3) The number of protons in the nucleus of an atom is the same as the a) electrons, and b) atomic number. 4) The large letter(s) that represent each element is called a symbol Complete the diagram by labeling all the parts. 5) electron (valence) 6) nucleus Made up of 7) protons and 8) neutrons 9) energy levels in the electron cloud 12) Complete the following table by placing a check in each bo that makes the statement true: Characteristic Electron Proton Neutron Has nearly no mass Positively charged Found in the nucleus Moves in energy levels Added together to make the mass number or atomic mass (weight) Does not have an electrical charge Negatively charged

3 13) Use the Periodic Table of the Elements to complete the following table. Note: Add the names and information for three elements of your own choosing: ELEMENT SYMBOL ATOMIC NUMBER MASS NUMBER * NUMBER OF PROTONS NUMBER OF ELECTRONS HYDROGEN H NITROGEN N CARBON C SODIUM Na CHLORINE Cl SILVER Ag Pick 3 more elements: Answers will vary F FLUORINE CALCIUM Ca MAGNESIUM Mg *Note: Remember to round off the atomic weight to obtain the mass number or atomic mass. In any neutral atom, the number of protons is always equal to the number of electrons.

4 #2 Subatomic Particles You will become more familiar with the atomic structure of some atoms by completing the chart below. For each element, you have been given enough information to fill in all the blanks. Use the periodic Table. Element Symbol Atomic Number Mass Number Number of Protons Numbers of Neutrons Number of Electrons Helium He Iodine I Neon Ne Zirconium Zr Aluminum Al Tungsten W Zinc Zn Krypton Kr Calcium Ca Boron B Sodium ion Na Sulfur ion S Chlorine Ion Cl Hydrogen Ion H (no, it s not a typo)

5 #3 Reactivity of Atoms In biology we are concerned about how atoms join each other to form molecules like hydrogen gas (H 2 ), carbon dioide (CO 2 ) and glucose (C 6 H 12 O 6 ). The tendency of atoms to bond with each other depends on their reactivity. The reactivity or combining capacity of an atom depends upon the arrangement of electrons in the outermost energy level, known as the valence. Circle the correct term in parenthesis for each sentence below. 1. If an atom s outermost energy level is completely filled with electrons (no vacancies), the atom considered ( stable / unstable ) and nonreactive. Therefore, it ( will / will not ) form bonds with other atoms. List three eamples of nonreactive elements: He, Ar, Ne On the Periodic Table, where do we find the nonreactive elements? The far right-hand period/group/column Nonreactive elements are also known as the Noble Gases. 2. If an atom s outermost energy level is not completely filled with electrons (vacancies present), the atom is considered ( stable / unstable ) and reactive. Therefore, it ( will / will not ) combine with other atoms. Eamples of reactive atoms: Element Symbol Atomic Number # electrons Draw the electrons in their energy levels Reactive (R) or non-reactive (NR) Carbon C 6 6 2) 4) R Hydrogen Oygen Nitrogen Magnesium Silicon Chlorine Argon H O N Mg Si Cl Ar 1 1 1) R 8 8 2) 6) R 7 7 2) 5) R ) 8) 2) R ) 8) 4) R ) 8) 7) R ) 8) 8) NR #4 Electrons and the Reactivity of Atoms

6 Directions: Place the answer to the following questions on the line provided. d 1. Energy levels are: a. the charge of protons c. the definite locations of electrons b. the charge of atoms d. the probable locations of electrons d 2. If an atom is reactive, how does it become stable? a. join a water molecule b. join the nuclei of other atoms c. form energy levels with other subatomic particles d. form bonds with other reactive atoms Directions: Smiley Cyrus was a student at Livingston High School. Below are her drawings of Bohr models for atoms of three different elements. Check Smiley Cyrus s work each diagram has TWO mistakes. Your task is to fi her errors. * P=protons N=neutrons E= Electrons = electrons in energy levels Nitrogen Argon Hydrogen Nitrogen: inner energy level should only have 2 electrons move one to the second energy level; also should be 7N instead of 7E in the nucleus. Argon: 22N in nucleus; should have a 3 rd energy level with 8 e- Hydrogen: Nucleus should have 1P instead of 0, and 0N instead of 1. Circle the atom(s) below that are reactive. Put a triangle around the atom(s) below that are nonreactive. N Ar H K C O He How many electron vacancies are in the valence of each of the following atoms? N 3 Ar 0 H 1 K 1 C 4 O 2 He 0

7 #5 Bohr Models and Lewis Dot Structures (Reference pages 3-5 of notes packet) 1. What is the maimum number of electrons that can be found in the first energy level? 2 2. What is the maimum number of electrons that can be found in the second energy level? 8 3. For any atom with an atomic number greater than 2, the maimum number of electrons that can be found in the outermost energy level (valence) is: 8. This is known as the Octet Rule. An atom with a full valence is nonreactive and stable. 4. Draw a Bohr Model and Lewis Dot Structure for each element below. Follow the eample given. Element Bohr Model Lewis Dot Structure Number of electron vacancies in valence Sulfur (S) 2 Phosphorous(P) 3 Fluorine (F) 1 Neon (Ne) 0

8 Lithium (Li) 7 #6 Bonding Patterns (Reference pages 3-5 of notes packet) 1) What is the purpose of bonding? _For atoms to become stable ( by gaining, losing, or sharing electrons.) 2) Is one atom of carbon stable? no Why or why not? it only has four electrons in its valence, which means 4 vacancies. 3) 4) How many electrons will an atom of carbon share with another atom in order to become stable? _4 5) List the two most common types of bonds that can form between atoms: a) covalent (sharing of e-) b) ionic (transfer of e-) 5) A chemical formula is a shorthand way of showing the types and numbers of atoms in a molecule or compound. For eample, H 2 O indicates that one atom of oygen has bonded with two atoms of hydrogen. Circle the correct term in parenthesis: The ( coefficient, subscript ) indicates how many atoms of the preceding element are found in the molecule. The (coefficient, subscript ) indicates how many molecules of each compound are present. In order to determine the number of atoms in a formula with a coefficient, ( multiply, add, divide ) the coefficient and the subscript. Any time you don t see a coefficient, you can assume it is 1 ; the same is true for a subscript. (eample: the chemical formula CO 2 indicates one molecule of carbon dioide which contains one atom of carbon and two atoms of oygen). Complete in the following chart: Chemical Formula Total Number of atoms of each element 2H 2 O Four hydrogen atoms and two oygen atoms. CaCO 3 One calcium atom and three oygen atoms. 2H 2 O Four hydrogen atoms and two oygen atoms. 6H 2 SO 4 Twelve hydrogen atoms, si sulfur atoms, and twenty-four oygen atoms Directions for drawing structural formulas: A structural formula is a drawing of the atoms in a compound and the number of bonds between atoms. The short lines in a structural formula represent a covalent bond (or a shared pair of e-) that has formed between two atoms. A single bond is represented by a single line (-). A double bond is shown with two lines (=). A triple bond would contain 3 lines ( ). Eample H 2 O or water : In one water molecule, there _2 atom(s) of hydrogen and 1 atom(s) of oygen. Hydrogen (H) has one electron and one vacancy in its valence. So, it needs bond(s) to be stable. Oygen (O) has si electrons in its valence (which means 2 vacancies). So, it needs bond(s) to be stable. By joining together, the atoms can share electrons in a way that makes all three atoms stable, each with a full valence. The compound is stable and neutral overall because the total #p is still equal to the total #e-. The way to represent this is to draw: H -- O -- H In this way, the two atoms of hydrogen are bonded with one atom of oygen. The hydrogen atoms each have one bond and the oygen atom has two bonds.

9 Try these eamples: (Reference pages 3-5 of notes packet) Draw the structural formulas for the following compound. Follow the models. H 2 # bonds each hydrogen can form? 1 N 2 # bonds each nitrogen can form? 3 H H N N CH 4 # bonds carbon can form? 4 each hydrogen? 1 H 2 O 2 # bonds each hydrogen can form? 1 each oygen? 2 H H C H H PCl 3 # bonds needed by each phosphorus? 3 each Cl? 1 H O O H O 2 # bonds needed by each oygen?2 Cl P Cl Cl O=O HCN (Hydrogen cyanide H 2 O H C N H O H

10 #7 Counting Atoms Calculate how many atoms of each element are present in each of the following (as written). 1. 3NaHCO 3 Na-3 H -3 C -3 O C 2 H 4 O 2 C-10 H-20 O Mg(OH) 2 Mg-2 O-4 H H 3 PO 4 H- 18 P-6 O H 2 SO 4 H-2 S-1 O-4 6. (NH 4 ) 3 PO 4 N-3 H-12 P-1 O-4 7. C 6 H 12 O 6 C-6 H-12 O CaCO 3 Ca-5 C-5 O- 15

11 #8 Recognizing Balanced Equations (Reference page 9 of notes packet) Remember, in a balanced chemical equation, the number of atoms of each element in the reactants will equal the number of atoms of each element in the products. EQUATION IS IT BALANCED, as written? (Y/N) A. 2C 2 H 6 + 5O 2 --> 2CO 2 + 6H 2 O N B. 2H 2 O 2 --> 2H 2 O + O 2 Y C. Na + O 2 --> 2Na 2 O N D. N 2 + 3H 2 --> 2NH 3 Y E. P 4 + 5O 2 --> P 4 O 10 Y F. 3Fe + 4H 2 O --> Fe 3 O 4 + 4H 2 Y G. C + 2H 2 --> CH 4 Y H. Al 2 O 3 --> Al + 3O 2 N I. H 2 + O 2 --> H 2 O 2 Y J. Na 2 SO 4 + CaCl 2 --> CaSO 4 + 2NaCl Y

12 #9 Balancing Equations Answer the following questions. Use complete sentences when given one or more lines to respond. State the Law of Conservation of Matter: Matter can neither be created or destroyed. To balance an equation, coefficient(s) may be added/removed/changed but subscripts cannot. Balance each of the following equations. H 2 + Cl 2 2HCl 4Fe + 3O 2 2Fe 2 O 3 C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O H 2 O + Cl 2 O 3 2HClO 2 2C 6 H O 2 12CO 2 + 6H 2 O 1) What is meant by the terms: products and reactants in a chemical equation? How do we know which is which? Products: ending materials (what is produced)_. Reactants: starting materials (what reacts). 2) Eplain what the subscript indicates. What does it mean if there is no subscript? Subscript = the number of atoms of the element indicated by the letter symbol preceding the subscript number. E. The 2 in H 2 O refers to the H, not the O. 3) Eplain what the coefficient indicates. What does it mean if there is no coefficient? Coefficient = the number of entire units of the formula (number of molecules) 4) Eplain why chemical equations must be balanced. # of atoms of each element in the reactants must = the # of atoms of each element in the products. This obeys the law of conservation of matter.