Chapter 4 Assessment
If a potassium atom has an atomic number of 19 and a mass number of 39, how many protons, electrons, and neutrons are in the atom?
19 protons, 19 electrons, and 20 neutrons.
A helium-4 atom has twice as many protons as a hydrogen atom. How many protons and neutrons are in the nucleus of a hydrogen-4 atom?
2 protons, 2 neutrons
The atomic number for iron is 26. How many neutrons are in the nucleus of an iron atom with a mass number of 57? How many electrons does the iron atom have?
31 neutrons, 26 electrons.
Scientists working in the field of nanotechnology use either a top-down or a bottom-up approach to construct tiny objects. Give an example of a visible structure that was made with a bottom-up approach and one that was made using the top-down approach.
Gears are made from the top down, buildings are made from the bottom up.
If an atom has an atomic number of 6 and a mass number of 14, how many electrons does the atom have? Explain.
The atom has 6 electrons because the amount of electrons is equal to the amount of neutrons in an atom.
J. J. Thomson demonstrated that electrons A. have a negative electric charge. B. have a positive electric charge. C. are repelled by a positively charged object. D. are attracted to a negatively charged object. E. do not have an electric charge.
A
One of the first people to state that matter is made up of atoms was A. Democritus. B. Aristotle. C. Dalton. D. Rutherford.
A.
The atomic number of sulfur is 16. How many electrons are there in an atom of sulfur-34? A. 16 B. 34 C. 18 D. 50
A.
The number of neutrons in an atom equals the A. Mass number minus atomic number. B. Atomic number plus number of electrons. C. Mass number plus atomic number. D. Atomic number minus mass number.
A.
What evidence convinced Dalton that elements must be made of individual particles called atoms?
All compounds have a fixed composition.
Electrons in the first energy level of an atom A. have no energy. B. have the lowest possible energy. C. have the highest possible energy. D. are in an excited state. E. are in an unstable state.
B
Most alpha particles pass through a thin layer of gold without deflection because gold atoms A. are filled with positively charged matter. B. have no overall charge. C. have a negatively charged nucleus. D. do not have a nucleus. E. have a dense nucleus surrounded by space.
B
Atoms emit energy as light when A. Electrons move to a higher energy level. B. Electrons move to a lower energy level. C. Protons move to a higher energy level. D. Protons move to a lower energy level.
B.
Dalton's model of an atom is best described as A. A solar system. B. A solid sphere. C. A plum pudding. D. An electron cloud.
B.
Which particle is the least massive? A. Proton B. Electron C. Neutron D. Nucleus
B.
What is the main difference between Bohr's model of the atom and the atomic theory that is currently accepted?
Bohr's model of the atom said that all electrons moved in fixed orbits around the nucleus, while the currently accepted atomic theory says that all atoms move randomly around the nucleus.
According to Dalton's atomic theory, an atom is A. made of smaller particles. B. a particle with a positive charge. C. the smallest particle of an element. D. in constant motion. E. a particle with a negative charge.
C
An electron configuration describes A. regions of space around the nucleus of an atom. B. possible energies that an electron can have. C. the arrangement of electrons in an atom. D. the emission of light from an excited atom. E. the number of possible orbitals in an atom.
C
All atoms of the same element have the same A. Mass number B. Number of isotopes C. Atomic number D. Number of neutrons
C.
Who provided the first evidence that atoms contain subatomic particles? A. Dalton B. Rutherford C. Thomson D. Bohr
C.
The atomic number of carbon is 6. The atomic number of nitrogen is 7. The atomic number of oxygen is 8. Name the isotope represented by an atom with 6 protons and 8 neutrons.
Carbon-14
If Oxygen-16 has 8 protons, 8 neutrons, 8 electrons, and is 99.757% of the oxygen in nature, and Oxygen-18 has 8 protons, 10 neutrons, 8 electrons, and is 0.205% of the oxygen in nature, what is the mass number of oxygen-18? A. 8 B. 10 C. 16 D. 18 E. 0.205
D
Almost all the mass of an atom is located in its A. Protons. B. Electrons. C. Electron cloud. D. Nucleus.
D.
An electron is a particle with A. A negative charge, found in the nucleus. B. A positive charge, found in the nucleus. C. No charge, found outside the nucleus. D. A negative charge, found outside the nucleus.
D.
Brightly colored neon lights consist of tubes filled with a gas. When an electric current passes through the tubes, different colors are emitted. Why might you conclude that the tubes in a multicolored display contained more than one element?
Each element only gives off one color, so multiple elements would be needed for multiple colors.
What does it mean to say that an atom is in an excited state?
The atom is at a higher energy level and therefore a higher orbital than normal.
The compound in blood that carries oxygen to cells around the body contains iron. Iron has an atomic number of 26. Iron-59 is used to diagnose different disorders in the blood. How is iron-59 different from all other isotopes of iron? How is it the same?
Iron-59 has a different number of neutrons than all other isotopes of iron, but it has the same number of protons as all the other isotopes of iron.
Compare the mass and volume of the nucleus to the total mass and volume of an atom.
It makes up almost all of the total mass of an atom, but only a small amount of the volume of an atom.
What evidence supported Thomson's theory that that the negatively charged particles he observed came from inside atoms?
No matter what metal Thomson used for the disk, the particles produced were identical; the particles had about 1/2000 the mass of a hydrogen atom (the lightest atom).
Which isotope of oxygen is represented by an atom with 8 protons and 9 neutrons—oxygen-16, oxygen-17, or oxygen-18?
Oxygen-17.
What is the difference between the atomic number of an atom and its mass number?
The atomic number tells the number of protons in an atom, while the mass number tells the amount of protons and neutrons combined.
How would the outcome of Thomson's experiment change if the beam were a stream of neutrons instead of a stream of electrons?
The beam would go straight to the opposite plate instead of bending to the positive plate.
In Thomson's experiment, why was the glowing beam repelled by a negatively charged plate?
The glowing beam was negatively charged.
Why were the proton and electron discovered before the neutron?
The neutron has no charge, while the proton and electron have charge, and are therefore easier to detect because they are repelled by something with the same charge as themselves.
Explain why a neutral atom cannot have one proton, one neutron, and two electrons.
The one proton only cancels out one electron, leaving the atom with a charge of -.
What part of Dalton's theory was modified after the discovery of isotopes?
The part stating all atoms of the same element have the same mass.
Compare the relative masses of protons, neutrons, and electrons in an atom.
The relative masses of protons and neutrons are equal, but the relative mass of an electron is 1/1836 of the relative mass of a proton.
If an experiment is set up like this: -A metal disk, one positively charged and one negatively charged, on either end of a sealed glass tube filled with gas at low pressure -A source of electric current attached with wires to each disk -A glowing beam going in between the disks, how is it a control for an experiment set up like this: -Same setup as before -A positive plate on one side of the tube, and a negative plate on the other side?
The second experiment causes the glowing beam to bend towards the positive plate, while the first experiment causes it to go straight to the plate on the other side, so it is a control because the variables of negative and positive charge had not been introduced.
The nucleus of an atom contains six protons and six neutrons. The nucleus of a second atom contains six neutrons and five protons. Are these atoms of different elements or isotopes of the same element? Explain your answer.
These are atoms of different elements because atoms of different elements have different numbers of protons.
Why must indirect evidence be used to study the structure of atoms?
We cannot directly see atoms, so we cannot use direct evidence.
If you see a green color when fireworks explode, can you be certain that the fireworks contained a barium compound? Give a reason for your answer.
You can because barium is the only element that gives off a green color.
