AnswersACE 2025-26 Physical Science B - SchellUnit Test

Unit Test — Unit test Answers

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Isra is analyzing the properties of several samples of elements to find out which sample is a metalloid. Which set of properties most likely belongs only to a metalloid?

A
forms basic compounds and is a solid
B
has a high luster and is very brittle
C
is a gas and has low electrical conductivity
D
is brittle and forms acidic compounds
2
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Who was the first chemist to organize elements by atomic number?

A
Johann Wolfgang Döbereiner
B
Antoine Lavoisier
C
Henry Moseley
D
John Newlands
3

Atoms of arsenic (As) are often added to silicon (Si) in a process called doping to change the conductivity of the silicon. How does the addition of arsenic change the conductivity of silicon?

A
An atom of arsenic has one fewer valence electron and more electron shells than an atom of silicon, so the conductivity decreases because the arsenic atom gains an electron.
B
An atom of arsenic has one more valence electron and more electron shells than an atom of silicon, so the conductivity decreases because the arsenic atom loses the electron.
C
An atom of arsenic has one fewer valence electron and fewer electron shells than an atom of silicon, so the conductivity increases because the arsenic atom gains an electron.
D
An atom of arsenic has one more valence electron and more electron shells than an atom of silicon, so the conductivity increases because the arsenic atom loses the electron.
4

Three radioisotopes are being discussed in a chemistry class. Technetium-99m has a half-life of 6 hours. Rubidium-87 has a half-life of 50 billion years. Which describes who would most likely use each isotope?

A
A geologist would use technetium-99m because short-life indicates an older organism, and a doctor would use rubidium-87 because it allows for a more-accurate measurement of disease.
B
A doctor would use technetium-99m because a short half-life indicates a quick measurement, and a geologist would use rubidium-87 because a longer half-life means that there is a longer time to measure old rock.
C
A doctor would use technetium-99m because a short half-life indicates a quick measurement, and an archeologist would use rubidium-87 because anything containing carbon also contains rubidium.
D
A geologist would use technetium-99m because a short half-life indicates an older organism, and an archeologist would use rubidium-87 because anything containing carbon also contains rubidium.
5

The model below shows an atom of an element.

Question illustration
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8
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9
1
16
6

Which statement describes the location of most metalloids on the periodic table?

A
The metalloids are located below metals and above nonmetals within a group.
B
The metalloids are located below nonmetals and above metals within a group.
C
The metalloids are located to the right of nonmetals and to the right of metals within a period.
D
The metalloids are located to the left of nonmetals and to the left of metals within a period.
7

Which important change in electronic devices, such as televisions and computers, is a result of the use of metalloids as semiconductors?

A
Electronic devices have become smaller.
B
Electronic devices are now more brittle.
C
Electronic devices now use more energy.
D
Electronic devices have become more expensive.
8

What best describes the states of nonmetals when they are at room temperature?

A
Most nonmetals are gaseous, but some are liquid or solid.
B
All nonmetals are gaseous unless they bond with a metal.
C
Most nonmetals are solids, but some are gaseous or liquid.
D
All nonmetals are solid unless they bond with a metal.
9

Rutherford used positively charged particles to investigate the structure of the atom. The results surprised him, and he developed the atomic model shown below.

Question illustration
A
A few positive particles bounced back because they bounced off of the net formed by the ovals.
A
A few positive particles bounced back because they were pushed away from the positive center.
M
Most positive particles passed through because of the empty space between the outer edge and the center.
M
Most positive particles passed through because they were attracted by the small particles moving around the center.
10

must

e
electrical charges.
n
numbers of neutrons.
a
atomic numbers.
e
energy levels.
11

Which is the property of nonmetals to evaporate easily?

A
brittle
B
dense
C
liquid
D
volatile
12

These models show the electron structures of two different nonmetal elements.

Question illustration
A
Element 1 is more reactive because it has fewer electron shells and is toward the top of its group on the periodic table.
B
Element 1 is more reactive because it has more electrons in its valence shell and is farther to the right on the periodic table.
C
Element 2 is more reactive because it does not have a valence shell close to the nucleus, so it will attract electrons.
D
Element 2 is more reactive because it does not have a full valence shell, so it will attract electrons.
13

Which radioactive isotopes did the Curies discover?

A
polonium and radium
B
radium and carbon-14
C
carbon-14 and uranium
D
uranium and polonium
14

Which describes radioactive decay of a substance?

A
More of the radioactivity is lost during the first half-life than in later half-lives.
B
More of the radioactivity is lost during the fourth half-life than in the first half-life.
C
Isotopes are the most stable during the first half-life.
D
Isotopes are the least stable during the later half-lives.
15

An atom of the element chromium has an atomic number of 24 and a mass number of 52. How many electrons are in an uncharged atom of chromium?

A
0
B
24
C
28
D
52

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