MINILAB 3

MINILAB 3.1Predicting the Prop= erties of Mystery Elements

When Mendeleev arranged the elements according to their atomic masses, some elements didn’t fit. He resolved this probl= em by predicting the existence and properties of elements that were unknown at= the time. In this MiniLab, you’ll predict some properties of two unknown elements.

OBJECTIVE:TO PREDICT PROPERTIES OF TWO ELEMENTS BASED UPON THE PROPERTIES OF SURROUNDING ELEMENTS.

HYPOTHESIS:

PROCEDURE

1. Unknown element A is in Group 14 below silicon a= nd above tin. Unknown element B is in Group 16 below sulfur and above telluriu= m.

2. The following information is given for the surro= unding elements and in this sequence: symbol, density in g/mL= , melting point in K, atomic radius in pm. Si, 2.= 4, 1680, 118; As, 5.72, 1087, 121; Sn, 7.3, 505, 1= 41; Ga, 5.89, 303, 134; S, 2.03, 392, 103; Br, 3.1, 266, = 119; Te, 6.24, 723, 138.

3. Refer to the locations of these elements on the portion of the periodic table shown here, and average the values of the four surrounding elements to predict the densities, melting points, and atomic r= adii of elements A and B.

OBSERVATIONS

Group 13	Group 14	Group 15	Group 16	Group 17
	Si 2.4 g/ml 1680 K 118 pm		S 2.03 g/ml 392 K 103 pm
Ga 5.89 g/ml<= /p> 303 K 134 pm	element A<= /p> ? g/ml ? K ? pm	As 5.72 g/ml<= /p> 1087 K 121 pm	element B<= /p> ? g/ml ? K ? pm	Br 3.1 g/ml 266 K 119 pm
	Sn 7.3 g/ml 505 K 131 pm		Te 6.24 g/ml<= /p> 723 K 138 pm

ANALYSIS

1. What are the identities of elements A and B?

2. How do your predicted values for the three prope= rties of element A compare with the actual values? Loo= k up the actual values in a chemical handbook or obtain them from your teacher.<= /span>

3. How do your predicted values for the three prope= rties of element B compare with the actual values?

4. If your predicted values are fairly close to the actual values, how do you explain the approximate correlation?