In the box below, draw the Lewis electron-dot structure for the compound formed from magnesium and oxygen. [Include any charges or partial charges.

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1 Name: 1) Which molecule is nonpolar and has a symmetrical shape? A) NH3 B) H2O C) HCl D) CH Page 1 2) When ammonium chloride crystals are dissolved in water, the temperature of the water decreases. What does this temperature change indicate about the dissolving of ammonium chloride in water? A) It is an endothermic reaction because it releases heat. B) It is an endothermic reaction because it absorbs heat. 3) Given the binary compound formed from magnesium and oxygen: C) It is an exothermic reaction because it releases heat. D) It is an exothermic reaction because it absorbs heat. In the box below, draw the Lewis electron-dot structure for the compound formed from magnesium and oxygen. [Include any charges or partial charges.] 4) Which element has the lowest electronegativity? A) fluorine B) nitrogen C) oxygen D) carbon 5) Which structural formula represents a polar molecule? Questions 6 through 9 refer to the following:

2 6) Is HCl a polar or a nonpolar molecule? [Explain why.] Page 2 7) State one way in which bond A and bond B are the same and one way in which they are different. 8) Draw Lewis electron-dot diagrams for the two molecules above. Label any partial charges. 9) Is Br2 a polar or a nonpolar molecule? [Explain why.] 10) Which atom has the strongest attraction for electrons? A) Cl B) F C) Br D) I 11) Which element would most likely form an ionic bond with chlorine? A) O B) K C) N D) S 12) Which compound contains a bond with the least ionic character? A) Li2O B) CO C) CaO D) K2O 13) What type of bonds are formed when metal atoms combine with nonmetal atoms? A) ionic bonds B) polar covalent bonds C) non-polar covalent bonds D) metallic bonds 14) The total number of pairs of shared electrons in a nitrogen molecule is A) 1 B) 2 C) 3 D) 4 15) What type of bond is formed between the two chlorine atoms in a chlorine molecule? A) polar covalent B) nonpolar covalent C) ionic D) metallic

3 16) Which molecule is nonpolar due to a symmetrical distribution of charge? Page 3 17) Given the reaction: H2 + Cl2 2HCl Which of the following statements best describes the energy change as bonds are formed and broken in this reaction? A) The forming of the HCl bond absorbs energy. C) The forming of the HCl bond releases energy. B) The breaking of the HH bond releases energy. D) The breaking of the ClCl bond releases energy. 18) Which electron-dot formula represents a nonpolar molecule? 19) What type of bonding is characteristic of a substance that has a high melting point and electrical conductivity only in the liquid phase? A) coordinate covalent B) ionic C) metallic D) nonpolar covalent 20) What type of bond is present in a water molecule? A) nonpolar covalent B) polar covalent C) ionic D) electrovalent 21) Which electron-dot diagram best represents a compound that contains both ionic and covalent bonds?

4 22) In the boxes below, draw a correct Lewis electron-dot structure for: (1) an atom of hydrogen (2) an atom of fluorine (3) a molecule of hydrogen fluoride (HF) Page 4 23) In a nonpolar covalent bond, electrons are A) shared equally by two atoms B) transferred from one atom to another Questions 24 and 25 refer to the following: C) located in a mobile "sea" shared by many ions D) shared unequally by two atoms Given the binary compound formed from potassium and iodine: 24) In the box below, draw the Lewis electron-dot structure for the compound formed from potassium and iodine. [Include any charges or partial charges.]

5 25) In the boxes below, draw the Lewis electron-dot diagrams for the elements K and I Page 5 26) Which type of bond exists in a molecule of hydrogen iodide? A) a polar covalent bond with an electronegativity difference between zero and 1.7 B) a nonpolar covalent bond with an electronegativity difference between zero and 1.7 C) a polar covalent bond with an electronegativity difference of zero D) a nonpolar covalent bond with an electronegativity difference of zero 27) Compounds with the greatest ionic character would form when fluorine reacts with A) noble gases B) metalloids (semimetals) C) alkali metals D) Group 13 elements 28) Which particles may be gained, lost, or shared by an atom when it forms a chemical bond? A) electrons B) protons C) neutrons D) nucleons 29) Which statement best describes all compounds? A) They can be decomposed by physical means. B) They can be decomposed by chemical change. 30) Which molecule contains a polar covalent bond? C) They contain at least three elements. D) They contain ionic bonds. 31) Which diagram best represents a polar molecule? 32) Which formula represents a v-shaped molecule? A) Br2 B) CaCl2 C) SO2 D) HBr

6 33) A crystalline solid has a high melting point and is a good conductor of electricity in the liquid state. This solid could be A) CO2 B) KCl C) C6H12O6 D) Hg Page 6 34) Which compound contains ionic bonds? A) Na2O B) CO C) CO2 D) N2O 35) Which change of phase is exothermic? A) solid to liquid B) liquid to gas C) gas to liquid D) solid to gas 36) Which formula represents a polar molecule? A) NH3 B) N2 C) Cl2 D) CH4 37) When a reaction occurs between atoms with the electron configurations and 2-7, what is the predominant type of bond formed? A) ionic B) metallic C) polar covalent D) nonpolar covalent 38) Which substance is made up of molecules that are dipoles? A) H2O B) CO2 C) CH4 D) N2 39) Which diagram best represents the structure of a water molecule? 40) The PCl bond in a molecule of PCl3 is A) electrovalent B) nonpolar covalent C) coordinate covalent D) polar covalent 41) Which compound contains both ionic and covalent bonds? A) CBr4 B) NaBr C) NaOH D) HBr 42) Which terms describe a substance that has a low melting point and poor electrical conductivity? A) ionic and molecular B) ionic and metallic C) covalent and metallic D) covalent and molecular 43) Which bond has the greatest degree of ionic character? A) HCl B) ICl C) KCl D) ClCl 44) Which phase change is exothermic? A) H2O() H2O(s) B) H2O(s) H2O(g) C) H2O() H2O(g) D) H2O(s) H2O() 45) The bonds present in silicon carbide (SiC) are A) London dispersion B) covalent C) ionic D) metallic 46) Which type of bond is formed between the carbon and oxygen atoms in a CO2 molecule? A) nonpolar covalent B) ionic C) electrovalent D) polar covalent

7 47) Which molecule contains a nonpolar covalent bond? Page 7 48) The table below lists four different chemical bonds and the amount of energy released when 1 mole of each of the bonds is formed. Which of the bonds is the most stable? A) HI B) HF C) HBr D) HCl 49) Which species can form a coordinate covalent bond with an H+ ion? 50