AnswersAA-F26 Physical ScienceRadioactivity

Radioactivity — Unit test Answers

12 verified answers
1
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While looking at bromine (Br) on the periodic table, a student needs to find another element with very similar chemical properties but with a different atomic mass. Which best describes the student’s options?

A
There are two possible elements, and they are directly to the left and right of bromine.
B
There are two possible elements, and they are directly above and below bromine.
C
There are many possible elements, and they are all in the same vertical column as bromine.
D
There are many possible elements, and they are all in the same horizontal row as bromine.
2
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A sample is in the second half-life. What percent of the sample is stable at this point?

A
12.5%
B
25%
C
50%
D
75%
3

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.
4

How does Rutherford’s model of the atom compare with Thomson’s model?

A
They both describe atoms as small, indivisible spheres.
B
They both describe electrons as moving around the nucleus.
C
They both describe electrons as being surrounded by the positive matter.
D
They both describe atoms as being made up of positive and negative matter.
5

must

e
electrical charges.
n
numbers of neutrons.
a
atomic numbers.
e
energy levels.
6

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
7

Particle A has very little mass in comparison to Particle B. Both particles are in the same atom. Which is the best conclusion about Particles A and B?

A
They have the same charge.
B
They are located in the nucleus together.
C
Particle A has a positive charge, and Particle B is neutral.
D
Particle A orbits the nucleus, and Particle B is located in the nucleus.
8

Who was the first chemist to organize elements by atomic number?

A
Johann Wolfgang Döbereiner
B
Antoine Lavoisier
C
Henry Moseley
D
John Newlands
9

Students are completing a table about a particular subatomic particle that helps make up an atom.What best explains how they should complete the table?

Question illustration
A
with “Inside the nucleus,” because the particle is a proton
B
with “Inside the nucleus,” because the particle is a neutron
C
with “Outside the nucleus,” because the particle is a proton
D
with “Outside the nucleus,” because the particle is an electron
10

Scientists have changed the model of the atom as they have gathered new evidence. One of the atomic models is shown below.

Question illustration
A
A few of the positive particles aimed at a gold foil seemed to bounce back off of the thin metallic foil.
B
Experiments with water vapor showed that elements combine in specific proportions.
C
Equations were used to identify regions around the nucleus where electrons would likely be.
D
Cathode rays were bent in the same way whenever a magnet was brought near them.
11

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.
12

An atomic physicist determines that an atom is composed of 8 positively charged particles and has a mass of 15 amu. Which is the best conclusion that can be drawn?

A
The atom has 7 neutrons and 8 protons.
B
The atom has 7 electrons and 8 protons.
C
The atom has 8 neutrons and 7 electrons.
D
The atom has 8 electrons and 7 protons.

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