CS 8 - CHAPTER 5 ASSESSMENT
20.- How many of the elements shown are metals? How many are nonmetals? How many are metalloids?
0 metals, 5 nonmetals, and 3 metalloid
3.- In a modern periodic table, elements are arranged in order of a.- atomic number b.- number of isotopes c.- atomic mass d.- number of neutrons
A
5.- An atomic mass unit is a.- one twelfth the mass of a carbon-12 atom b.- the mass of a carbon-12 atom c.- the mass of a neutron d.- the mass of a proton
A
17.- In general, what happens to the reactivity of elements in groups labeled A as atomic numbers increase across a period?
Across a period from left to right, metals become less reactive and nonmetals become more reactive, excluding the elements in Group 8A.
15.- Explain how the atomic mass of an element is affected by the distribution of its isotopes in nature.
An atomic mass is a weighted average of the atomic masses of an element's isotopes. The distribution of the isotopes determines how much each isotope affects the weighted average
4.- How many periods does the periodic table have? a.- 18 b.- 7 c.- 9 d.- 8
B
6.- An element that is shiny and conducts electric current is likely to be a a.- gas b.- metal c.- metalloid d.- nonmetal
B
8.- Elements that have the same number of valence electrons are a.- in the same period b.- in the same group c.- called noble gases d.- called transition metals
B
25.- An element on the periodic table has two naturally occurring isotopes. One isotope has an atomic mass of about 10 amu. The other isotope has an atomic mass of about 11 amu. What is the name of this element?
Boron, with an atomic mass of 10.81
21.- Which elements is a liquid at room temperature and which is a gas at room temperature?
Bromine is a liquid and chlorine is a gas.
1.- Mendeleev arranged the elements in his periodic table in order of a.- Atomic number b.- Number of electrons c.- mass d.- number of neutrons
C
9.- The most reactive metal are the a.- transition metals b.- alkaline earth metals c.- alkali metals d.- metalloids
C
27.- Applying Concepts - Why are samples of the alkali metal cesium usually stored in argon gas?
Cesium is an extremely reactive metal; argon is an extremely unreactive nonmetal.
22.- Which of the two halogens shown is more reactive? Give a reason for your answer.
Chlorine is more reactive than bromine because the reactivity of nonmetals increases from the bottom to the top of a group.
10.- Which elements are all gases at room temperature? a.- Group 1A b.- Period 3 c.- Group 7A d.- Group 8A
D
2.- Mendeleev's decision to leave gaps in his periodic table as supported by the discovery of a.- electrons b.- protons c.- argon d.- gallium
D
7.- Copper is an example of a.- an alkali metal b.- an alkaline earth metal c.- nonmetal d.- a transition metal
D
16.- List three ways that the elements in the periodic table can be classified.
Elements can be classified by their state at room temperature; by whether they exist in nature; and by whether they are metals, nonmetals, or metalloids
18.- Why don't the elements within an A group in tehe periodic table have identical properties?
Elements in the same A group do not have identical properties because their valence electrons are in different energy levels.
28.- Applying Concepts - Why are halogens found in nature only in compounds?
Halogens are always found in nature in compounds because halogens are highly reactive nonmetals.
11.- What information did Mendeleev have about the elements he organized into a periodic table?
Mendeleev Knew their relative masses and properties.
12.- How did Mendeleev know where to leave the spaces in this table?
Mendeleev placed elements in the groups where they logically belonged based on their properties.
23. Does selenium have more in common with sulfur or bromine? Explain your answer.
Selenium has more in common with sulfur because they are in the same group and have the same number of valence electrons.
29.- Applying Concepts - Which element on the periodic table has chemical properties that are most similar to those of carbon?
Silicon
19.- Why was it difficult to discover the noble gases?
The noble gases were difficult to discover because they are colorless, odorless, and very rarely react.
14.- Why does the number of elements vary from period to period?
The number of elements per period varies because the number of available orbitals increases as the energy level increases.
13.- Why is the table of the elements shown in Figure 7 called a periodic table?
The table is called a periodic table because the properties of the elements repeat at regular intervals from row to row.
24.- If you know that an elements is a solid at room temperature, do you have enough data to classify the elements as a metal, metalloid or nonmetal? If you now that the element is a gas at room temperature, do you have enough data? Explain your answer.
There is not enough data for the solid because solids at room temperature can be metals, nonmetals or metalloids. There is enough data for the gas because there are no gaseous metals or metalloid at room temperature.
30.- Designing Experiments - If you were trying to make a compound of the noble gas xenon, would you use nitrogen or fluorine? Explain your choice.
You would choose fluorine because it is much more likely to react than nitrogen is.
26.- How many valence electrons would an element with atomic number 113 have?
three
