Answers GCSS_Physical Science_ICRadioactivity

Unit Test Answers

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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?

There are two possible elements, and they are directly to the left and right of bromine.

There are two possible elements, and they are directly above and below bromine.

There are many possible elements, and they are all in the same vertical column as bromine.

There are many possible elements, and they are all in the same horizontal row as bromine.

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Which radioactive isotopes did the Curies discover?

polonium and radium

radium and carbon-14

carbon-14 and uranium

uranium and polonium

A sample is in the second half-life. What percent of the sample is stable at this point?

12.5%

25%

50%

75%

Which is the property of nonmetals to evaporate easily?

brittle

dense

liquid

volatile

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

Electronic devices have become smaller.

Electronic devices are now more brittle.

Electronic devices now use more energy.

Electronic devices have become more expensive.

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?

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.

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.

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.

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.

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

They both describe atoms as small, indivisible spheres.

They both describe electrons as moving around the nucleus.

They both describe electrons as being surrounded by the positive matter.

They both describe atoms as being made up of positive and negative matter.

Sonya is studying a nonmetal element. She learns that the element is like other elements in its group because it can bond to form a salt or an acid. She also learns that the element is the most reactive element in its group. Which element is Sonya most likely studying?

sulfur (S)

neon (Ne)

fluorine (F)

iodine (I)

must

electrical charges.

numbers of neutrons.

atomic numbers.

energy levels.

Which scientist believed that the probable, not exact, location of the electrons of an atom can be determined by using mathematics?

Rutherford

Bohr

Dalton

Schrödinger

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?

forms basic compounds and is a solid

has a high luster and is very brittle

is a gas and has low electrical conductivity

is brittle and forms acidic compounds

Which metal is most likely to form more than one kind of positively charged ion?

sodium (Na)

barium (Ba)

nickel (Ni)

magnesium (Mg)

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?

They have the same charge.

They are located in the nucleus together.

Particle A has a positive charge, and Particle B is neutral.

Particle A orbits the nucleus, and Particle B is located in the nucleus.

Where are alkaline earth metals found on the periodic table?

Group 1

Group 2

Groups 3–12

Group 17

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

Johann Wolfgang Döbereiner

Antoine Lavoisier

Henry Moseley

John Newlands

Which describes radioactive decay of a substance?

More of the radioactivity is lost during the first half-life than in later half-lives.

More of the radioactivity is lost during the fourth half-life than in the first half-life.

Isotopes are the most stable during the first half-life.

Isotopes are the least stable during the later half-lives.

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?

with “Inside the nucleus,” because the particle is a proton

with “Inside the nucleus,” because the particle is a neutron

with “Outside the nucleus,” because the particle is a proton

with “Outside the nucleus,” because the particle is an electron

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

A few of the positive particles aimed at a gold foil seemed to bounce back off of the thin metallic foil.

Experiments with water vapor showed that elements combine in specific proportions.

Equations were used to identify regions around the nucleus where electrons would likely be.

Cathode rays were bent in the same way whenever a magnet was brought near them.

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

The metalloids are located below metals and above nonmetals within a group.

The metalloids are located below nonmetals and above metals within a group.

The metalloids are located to the right of nonmetals and to the right of metals within a period.

The metalloids are located to the left of nonmetals and to the left of metals within a period.

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?

The atom has 7 neutrons and 8 protons.

The atom has 7 electrons and 8 protons.

The atom has 8 neutrons and 7 electrons.

The atom has 8 electrons and 7 protons.

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