Phys Sc 436                                        

Pretest 1.3 with answers

 

 

 

1.         Which 3 of the following elements would you place in the same family, based on their properties? Justify your choice.

 

Element

Melting Point(0C)

Common Ion(s)

Conducts electricity?

Appearance

chlorine

-101

-1

no

Yellow-green

barium

714

2

yes

Shiny, silvery

Antimony

631

3,-3,5

no

Dull grey

Copper

1083

2,1

yes

Shiny ,orange

Gold

961

3,1

yes

Shiny, yellow

silver

1063

1

yes

Shiny, silvery

 

 

 

 

 

 

Copper, gold and silver are all high-melting and shiny. They all conduct and form the +1 ion.

 

2.         Explain why +1 is the common ion for alkali metals.

 

By losing one valence electron, alkali metals become isoelectronic with noble gases.

 

3.         What noble gas and what charged alkaline earth metal have the same shell diagram as K+1?

           

Ar and Ca+2

 

 

4.         Which of the following is NOT found in nature?

 

a.         Ar                    b.         Ba                    c.         F-1                    d.         K+1

 

Ba ( no full shell)

 

5.         How can you distinguish between lithium and iron without weighing or heating them and without reacting them with anything?

 

Lithium, like all alkali metals, is soft and can be cut with a knife. Iron can't.

 

6.         What happens when lithium is added to water?

 

It reacts to form a base and hydrogen gas.

 

7.         How can you prove that the reaction between calcium and water generated hydrogen and lime

(an acid –destroying substance that can be turned into limewater)?

 

Test for hydrogen: flaming test will result in a pop.

Blow CO2 into lime + water and it should go cloudy.

 

8.         What is the common ion formed by alkaline earth metals?

 

+2

 

9.         List three substances that will react with alkaline earth metals.

 

Acids, water, halogens

 

10.        Why are they called alkaline earth metals?

 

Alkaline = bases are formed when water is added to them

Earth = their bases are poorly soluble in water, like mud

 

11.        Explain why halogens form diatomic molecules. Use dot and shell diagrams in your explanation.

 

By sharing one electron each, both atoms fill their shells.

 

 

 


 F           F

 

 

 

 


12.        I am an element that likes to form the -1 ion, and I have the smallest nucleus among the members of my family. What am I?

 

 

            F

 

14.        The noble gases don’t burn. Why not?

 

            They are already have the stable shell diagrams that many other families try to imitate.

 

 

15.        Which TWO of the following atomic models represent elements from the halogen family?

 

 

 

            2 and 3. (1 cannot have 7 electrons in the first shell; max = 2)

 

16.        How do you distinguish between a thin plate of silicon from a plate of silver? List a chemical test and a physical test.

 

            Silicon is not malleable. Silver is.

            Silicon does not tarnish; silver reacts with pollutants in the air and turns black.

 

17.        With the exception of Se, every other nonmetal can be distinguished from metalloids by sight alone. How?

 

            All metalloids are grey. With the exception of Se, all non metals are not grey.

 

18.        Draw appropriate dot structures for the following: Solutions

 

a.         C6H12

b.         OF2

c.         KI

d.         C8(NO2)8          This structure should be the most symmetric possible. It is the world's most powerful chemical explosive.

 

           

 

 

 

Flashback[1]:                            

 

19.        Which of the following involves a chemical change?

 

1.  Boiling water______

2.  Putting sugar in coffee_____

3.  Toasting two slices of bread____

4.  Spreading jam on toast_____

 

answer: 3

 

 

20.        Which of the following is a characteristic property of mercury (Hg)?

 

A)

 

Is has a metallic luster.

 

C)

 

It is gray.

 

B)

 

It evaporates slowly.

 

D)

 

Its melting point is -39°C

 

            answer: D



[1] Flashback: an unexpected but vivid recurrence of a past experience (especially a recurrence of the effects of a previous test taken much earlier)