Unit 1: the Periodic Trends and Bonding (Version A)

Name: ______K: /30 C: /17 I: /12 A: /12

Unit 1: The Periodic Trends and Bonding (Version A)

Part 1: Multiple Choice [K - 20 marks]

Identify the letter of the choice that answers the question. Place your answer on the scantron card using pencil.

1. Consider the equation X(g) + energy ® X+ + e–. The "energy" term in the equation represents

2. Electron affinity increases as you go from left to right on the periodic table because

3. Two atoms are isotopes if they have

4. The atomic mass of barium is due to the number of

5. Isotopes are

a. atoms with the same number of neutrons but different number of protons

b. atoms with the same number of protons but different numbers of neutrons

c. atoms with the same number of neutrons plus protons but different number of neutrons and of protons

d. atoms with the same number of prptons and electrons

e. atoms with the same number of neutrons and electrons

6. The mass listed for each element in the periodic table is

7. Why does atomic radius increase from top to bottom in a chemical family?

8. Why does atomic radius decrease from left to right in a period?

9. Which of the following is the most reactive element?

10. Elements X and Y are in the same chemical family. Element X has a first ionization energy of 7.646 eV. Element Y has a first ionization energy of 5.695 eV. Which is more reactive?

11. Choose the pair of elements that will form a compound having bonds with the most ionic character:

a.  Li and I b. C and O c. Fr and F d. K and Cl

12. According to the Lewis model of the atom, the number of bonding electrons in a nitrogen atomis

a. 1 b. 2 c. 3 d. 5 e. 7

13. Which of the following atoms is believed to contain three lone pairs of electrons?

14. A student records the following evidence in a lab book.

Which of the substances shown in the table above is most likely an ionic compound?

15. The concept of multiple covalent bonds is used to explain the molecular formula of

16. Which of the following is the proper electron dot diagram for NaCl?

17. The particle that has the smallest mass is the

18. The atomic number of an element is defined as the

19. The relative atomic mass of chlorine (35.452 u) is a good indication that

a. chlorine is a compound, not an element d. chlorine consists of the molecule Cl2

b. chlorine is a mixture of isotopes e. chlorine is radioactive

c. chlorine nuclei contain fractions of a neutron

20. Which of the following elements requires the least amount of energy to remove an electron from an atom to form an ion?

Unit 1: The Periodic Trends and Bonding (Version A)

Part 2: Nomenclature [K/U – 10 marks]

1.  Complete the following chart by filling in the name or formula as required.

Part 3:Completion [C – 5 marks]

Complete each sentence or statement. Write you answer in the space provided.

1. Electrons in the outermost energy level of an atom or molecule are called ___fluorine______electrons.

2. Electron transfers result from the large difference in ___valence______between metals and nonmetals.

3. The number of covalent bonds that an atom can form is known as its ______bonding capacity______.

4. The atomic radii of nitrogen, oxygen, and fluorine are 70 μm, 66 μm, and 64 μm, respectively. One would expect that of the three, the atom with the lowest electron affinity would be _____electronegativity______.

5. The atomic radii of nitrogen, oxygen, and fluorine are 70 μm, 66 μm, and 64 μm, respectively. One would expect that of the three, the atom with the highest electronegativity would be ______nitrogen______.

Part 3: Short Answer [C –12 marks]

Answer the questions in the spaces provided. Marks allocated for each question are indicated in brackets after the question.

1.  Complete the following table: (8 marks)

2. Explain how the number of energy levels (shells) in an atom affects electronegativity. (2 marks)

•  As the number of shells increase, the atomic radii also increases, electronegativity of atom goes down

•  More shells result in greater shielding effect; barriers to attractive forces

•  Decreasing attractive forces for valence electrons and other electrons implies that the atom have a weaker power to attract shared pair of electrons to itself, therefore its electronegativity is lower

3. Explain why the reactivity of metals is different than that of non-metals. (2 marks)

•  Metals give up electrons forming +ve ions

•  Non-metals react by gaining electrons forming –ve ions

Part 4: Putting It Together [ T/I – 12 marks]

1. For a science fair project, a student wants to design a simple device for removing certain gases from polluted air. He knows that polar molecules dissolve well in water, so he bubbles polluted air through a jug of water to remove unwanted gases. For his project, the student uses air containing the following gases:

Using your knowledge of polar molecules, determine which gases will be removed from the polluted air. Include structural diagrams in the spaces provided to support your answer. (8 marks)

Compounds 1,5,7, 8 will be removed

3.  Two molecules, methane and water, are similar in size, yet their melting points are very different. The boiling point of methane, CH4, is -161°C, while the boiling point of water, H2O, is 100°C. Why does this difference in boiling points occur? Use diagrams to assist with your explanation. (4 marks)

•  CH4 methane, non-polar, tetrahedral, non-polar, london forces only (weak intermolecular forces), low BP and MP

•  H2O water bent structure and polar molecule dipole-dipole forces, hydrogen bonding, greater ionic character, therefore higher MP and BP

Part 5: Analysis [MC – 11 marks]

1.  You might have heard advertisements about detergents that “break up grease”. Oil and grease consist of large non-polar molecules, which are very insoluble in water. Nevertheless, detergents, which seem to dissolve in water, can remove oil and grease from clothing in water. A space filling model of a typical detergent molecule is shown below. Study the model, and provide a possible explanation for how detergents can remove grease from clothing. (4 marks)

Non-polar Polar

•  Water imporives the detergents ability to solubilize the grease by attaching itself to the polar end and

•  Non-polar end of greese molecule (detergent) interacts with grease (non-polar)

•  This emulsifier interaction (water-detergent) allows the greasy ends to become solubule in water and together with vigorous rubbing, removes the grease and dirt from clothes.

2.  The elements in the hypothetical universe, Omega Orion, have many similarities to the elements found in our own universe. The periodic table of the elements in Omega Orion is given below. Explain which of the following compounds in Omega Orion would NOT have the following formulas: [8 marks]

S2, OZ, US, PY2, OR2, VY3, SY, U2X

1+ 2+ 3- 2- 1- 0

•  Use criss-cross rule to see what can form

Forms S2 , US, PY2, U2X

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