Ch. 4 Physical Science study guide - Atomic Structure

If an atom of an element has a mass number of 32 and 20 neutrons in its nucleus, what is the atomic number of the element?

12

What is the maximum number of electrons that an atomic orbital can contain?

2

If 2 grams of element X combine with 4 grams of element Y to form compound XY, how many grams of element Y would combine with 14 grams of X to form the same compound?

28 grams

If an atom of tin has a mass number of 118 and an atomic number of 50, how many neutrons are in its nucleus?

68

If an atom has 34 protons and 40 neutrons, what is its mass number?

74

A sample of calcium contains calcium-40, calcium-44, calcium-42, calcium-48, calcium-43, and calcium-46 atoms. Explain why these atoms can have different mass numbers but must have the same atomic number.

All the atoms of an element have the same atomic number because the atomic number equals the number of protons in an atom. If one of the atoms had a different number of protons, the atom would not be a calcium atom. The mass number can vary because it is the sum of the protons and neutrons, and isotopes of an element can have different numbers of neutrons.

Which statement about subatomic particles is true?

An electron has far less mass than either a proton or neutron

Which statement about electrons and atomic orbitals is NOT true?

An electron has the same amount of energy in all orbitals.

What is the difference between an orbital and the electron cloud?

An orbital is a region of space around the nucleus where an electron is likely to be found. The electron cloud is a visual model that represents all the orbitals in an atom.

Protons have a positive charge, while neutrons have no charge. This atom has an atomic number of 8 and a mass number of 17.

Analyzing Data What is the charge on the subatomic particles represented in Figure 4-3? Assuming all the particles in the nucleus are visible, what are the atomic and mass numbers of the atom shown?

According to ____________________, all matter was made up of four elements — earth, air, fire, and water.

Aristotle

Which of the following is NOT part of John Dalton's atomic theory?

Atoms contain subatomic particles.

Why is Bohr's model of the atom often called the planetary model?

Bohr's atomic model represents electrons as moving in fixed orbits around the nucleus like planets moving in orbits around a sun.

What did Bohr's model of the atom do that Rutherford's model did not?

Bohr's model focused on electrons.

Panel 1 depicts an atom as a solid sphere without any subatomic particles. Panel 2 shows an atom that has a subatomic structure.

Comparing and Contrasting In Figure 4-2, what is the main difference between the atomic model in panel 1 and the model in panel 2?

The main difference is the way in which electron motion is depicted. In panel 2, the movement of electrons is represented by fixed circular orbits. In panel 3, the probable locations of the moving electrons are represented by a cloud.

Comparing and Contrasting In Figure 4-2, what is the main difference between the atomic model in panel 2 and the model in panel 3?

What did Democritus believe about matter?

Democritus believed all matter consisted of tiny particles that could not be divided into smaller particles.

Which statement accurately represents the arrangement of electrons in Bohr's atomic model?

Electrons travel around the nucleus in fixed energy levels with energies that vary from level to level.

It is helpful because it shows the general locations of the subatomic particles in an atom. It is not helpful because it implies that electrons travel in fixed paths around the nucleus.

Evaluating In Figure 4-2, how is the atomic model in panel 2 helpful to your understanding of the atom? In what ways is it not helpful?

Students may answer yes because the model shows the composition of the nucleus of an atom. Students may answer no because the model does not include any electrons or show the position of the nucleus in the atom.

Evaluating Is Figure 4-3 a useful model of an atom? Explain your answer.

nuclei

In Rutherford's gold foil experiment, shown in Figure 4-1, alpha particles that bounce straight back from the foil have struck ____________________ in the gold atoms.

Dalton probably would not have recognized this model because he thought of the atom as a solid indivisible ball and had no knowledge of subatomic particles.

Inferring Would Dalton have recognized the model of a nucleus shown in Figure 4-3? Explain your answer.

Yes; Rutherford demonstrated the existence of a nucleus, named subatomic particles with a positive charge protons, and predicted the existence of neutrons.

Inferring Would Rutherford have recognized the model of a nucleus in Figure 4-3? Explain your answer.

Yes; they go from the simplest (the solid sphere in 1) to the most complex (the electron cloud model in panel 3). Students may specifically cite John Dalton in connection with panel 1 and Niels Bohr in connection with panel 2 to support their answer.

Interpreting Graphics Are the atomic models in Figure 4-2 arranged in the order that they were developed? Explain your answer.

How was Bohr's atomic model similar to Rutherford's model?

It described a nucleus surrounded by a large volume of space.

Which statement best describes Rutherford's model of the atom?

It is like a huge stadium with a positively charged marble at the center.

How does the electron cloud model of the atom represent the locations of electrons in atoms?

It provides a visual model of the most likely locations of electrons in an atom.

Which statement about subatomic particles is NOT true?

Protons and neutrons have the same charge.

Who provided evidence for the existence of a nucleus in an atom?

Rutherford

What did Rutherford conclude about the location of positive charge in an atom?

Rutherford concluded that positive charge was concentrated in the nucleus of an atom.

What can scientists measure to provide evidence that electrons can move from one energy level to another?

Scientists can measure the energy gained when electrons absorb energy and move to a higher level or the energy released when the electrons return to a lower energy level.

How did the results of J.J. Thomson's experiments change how scientists thought about atoms?

Scientists realized that atoms contained smaller subatomic particles.

What is the difference between an atom in the ground state and an atom in an excited state?

The atom in an excited state has more energy and is less stable than the atom in the ground state.

How does the state of atoms in a neon light change when light is emitted?

The atoms return from an excited state to the ground state.

What can you assume has happened if an electron moves to a higher energy level?

The electron has gained energy.

Suppose an atom has a mass number of 23. Which statement is true beyond any doubt?

The number of protons in the nucleus does not equal the number of neutrons.

Inferring Why do you think the proton was discovered before the neutron? (Hint: Consider the properties of protons and neutrons.)

The proton has a positive charge, but the neutron has no charge. It was easier to detect the existence of a charged particle because its path could be deflected by a charged plate.

Rutherford's gold foil experiment provided evidence for which of the following statements?

There is a dense, positively charged mass in the center of an atom.

Which statement is true about oxygen-17 and oxygen-18?

They are isotopes of oxygen.

Why did Rutherford propose a new model of the atom after seeing the results of the gold foil experiment?

Thomson's model no longer explained all the available evidence. In Thomson's model, for example, positive charge was spread evenly throughout the atom. Rutherford had concluded that the positive charge of an atom was concentrated in the center of the atom.

The solid ball in panel 1 is like the drawing of the exterior of a house. It provides no details about the internal structure of an atom. The model in panel 2 shows the locations of different parts of the atom within the atom and their relative sizes. It is like a blueprint that shows the size and location of rooms in a house.

Using Analogies Read the following analogy and explain how it applies to panels 1 and 2 in Figure 4-2: The atomic model in panel 1 is to the model in panel 2 as a drawing of the outside of a house is to a blueprint of the inside.

Explain what the colors in a fireworks display reveal about the movement of electrons in atoms.

When fireworks explode, the heat produced by the explosions causes some electrons in atoms to move to higher energy levels. When the electrons return to lower energy levels, some of the energy is released as visible light. The colors vary because each element has a different set of energy levels.

Which of the following provides the best analogy for an electron in an atomic orbital?

a bee trying to escape from a closed jar

Which of the following most accurately represents John Dalton's model of the atom?

a tiny, solid sphere with a predictable mass for a given element

In Rutherford's gold foil experiment, some of the _________________________ aimed at gold atoms bounced back, suggesting that a solid mass was at the center of the atom.

alpha particles

The Greek philosopher Democritus coined what word for a tiny piece of matter that cannot be divided?

atom

What scientific word comes from a Greek word meaning "uncut"? Which Greek philosopher first used the word to describe matter?

atom; Democritus

The number of protons in one atom of an element is that element's

atomic number

In the nucleus of an atom, there are 18 protons and 20 neutrons. What are the atomic number and mass number of this isotope?

atomic number = 18; mass number = 38

To find the number of neutrons in an atom, you would subtract

atomic number from mass number

Unlike Democritus, Aristotle did not believe that matter was composed of tiny, indivisible ____________________.

atoms

The moving blades of an airplane propeller provide an analogy for the electron ____________________ model.

cloud

John Dalton observed that elements always combine in the same ratio to form a particular ____________________.

compound

In an atomic model that includes a nucleus, positive charge is

concentrated in the center of an atom.

J. J. Thomson's experiments provided evidence that an atom

contains negatively charged particles.

Which of the three subatomic particles—proton, electron, or neutron—has the least mass?

electron

Which subatomic particle has a negative charge?

electron

In Bohr's model of the atom, ____________________ move in fixed orbits around the nucleus.

electrons

When an atom gains or loses energy, some of its ____________________ may move between energy levels.

electrons

John Dalton concluded that all the atoms of a single ____________________ have the same mass.

element

An atom in which an electron has moved to a higher energy level is in a(an) ____________________ state.

excited

When all the electrons in an atom are in orbitals with the lowest possible energy, the atom is in its ____________________ state.

ground

Most calcium atoms have an atomic number of 20 and a mass number of 40, but some calcium atoms have a mass number of 48. What word could you use to describe these two kinds of calcium atoms?

isotopes

In Niels Bohr's model of the atom, electrons move

like planets orbiting the sun.

The ____________________ of an isotope is the sum of the number of protons and neutrons in its nucleus.

mass number

The glowing of a neon light is caused by electrons emitting energy as they

move from higher to lower energy levels.

The subatomic particle that J. J. Thomson discovered has a(an) ____________________ charge.

negative

The difference between a sample of heavy water and regular water is that a hydrogen atom in heavy water has an extra ____________________.

neutron

Protons and ____________________ are found in the nucleus of an atom.

neutrons

The nuclei of isotopes contain different numbers of ____________________.

neutrons

The diagram in Figure 4-1 shows the results of Rutherford's gold foil experiment. What caused some of the alpha particles to bounce straight back from the gold foil?

nuclei in the gold atoms

The results of Rutherford's gold foil experiment demonstrated that the ____________________ occupies a very small amount of the total space inside an atom.

nucleus

If element Q has 11 protons, its atomic ____________________ is 11.

number

The region in which an electron is most likely to be found is called a(an) ____________________.

orbital

What do scientists use to predict the locations of electrons in atoms?

probability

Neutrons and ____________________ have almost the same mass.

protons

Democritus thought that matter was made of tiny particles

that could not be divided.

What does the electron cloud model describe?

the most likely locations of electrons in atoms

Which of the following is unique for any given element?

the number of protons

According to John Dalton's observations, when elements combine in a compound,

the ratio of their masses is always the same.