Chapter 3 Review: Atoms and Moles

Question 1

What is the Law of Conservation of Mass?

Answer 1

Mass cannot be created nor destroyed during ordinary chemical and physical changes.

Question 2

What is atomic theory?

Answer 2

Atoms are the building blocks of all matter.

Question 3

What is the Law of Definite Proportions?

Answer 3

A chemical in a compound always contains the same elements in exactly the same proportions by weight or by mass

Question 4

What is the Law of Multiple Proportions?

Answer 4

When 2 elements combine to form two or more compounds, the mass of one element that combines with a given mass of the other is in the ratio of small whole numbers

Question 5

What are the five principles in Dalton’s atomic theory?

Answer 5

1. All matter is composed of extremely small particles called atoms (cannot be subdivided, created, or destroyed)
2. Atoms of given elements are identical in their physical and chemical properties.
3. Atoms of different elements differ in their physical and chemical properties.
4. Atoms of different elements combine in simple, whole number ratios to form compounds.
5. In chemical reactions, atoms are combined, separated, or rearranged but never created, destroyed, or changed.

Question 6

What are alpha particles?

Answer 6

A small positively charged particle, which Rutherford used directed at the gold foil.

Question 7

What is a neutron?

Answer 7

A subatomic particle that has no charge and is part of the nucleus.

Question 8

What is an electron?

Answer 8

Subatomic particle that has a negative charge

Question 9

What is a proton?

Answer 9

A subatomic particle that has a positive charge and is part of the nucleus. The number of these particles is determined by the identity of the element.

Question 10

What is a nucleus?

Answer 10

An atom’s central region, which is made of protons and neutrons.

Question 11

What is an isotope?

Answer 11

An atom that has the same number of protons as other atoms of the same element, but has a different number of neutrons.

Question 12

What is a mass number?

Answer 12

The sum of the number of protons and neutrons of the nucleus of an atom.

Question 13

What is an atomic number?

Answer 13

The number of protons that compose the nucleus of the atoms; number is the same for all atoms of an elements.

Question 14

What is the photoelectric effect?

Answer 14

Occurs when light strikes a metal and electrons are released.

Question 15

What is the ground state?

Answer 15

The lowest energy state of a quantized system.

Question 16

What is an electron configuration?

Answer 16

The arrangement of electrons in an atom.

Question 17

What is an excited state?

Answer 17

an atom has more energy than it does at its ground state.

Question 18

What is a quantum number?

Answer 18

A number that specifies the properties of electrons in an atom.

Question 19

What is an orbital?

Answer 19

highest probability of locating an electron

Question 20

What is the electromagnetic spectrum?

Answer 20

All the frequencies of wavelengths of electromagnetic radiation

Question 21

What is the Aufbau Principle?

Answer 21

each successive element is obtained by adding one proton to the nucleus of the atom and one electron to the lowest-energy orbital that is available.

Question 22

What is the Pauli Exclusion Principle?

Answer 22

States that two particles of a certain class cannot be in the exact same energy state.

Question 23

What is Hund’s Rule?

Answer 23

for an atom in the ground state, the number of unpaired electrons is the maximum possible and these unpaired electrons have the same spin.

Question 24

What is quantum theory?

Answer 24

The present day model of an atom, in which electrons are located in orbitals.

Question 25

What is the line-emission spectrum?

Answer 25

The spectrum of a few colors seen through a prism made when high-voltage current is passed through a tube of hydrogen gas at low pressure.

Question 26

List the four quantum numbers and their significance.

Answer 26

1st Quantum-> Principal Quantum Number (n); corresponds to the row number on the periodic table
2nd Quantum->Angular Momentum Quantum Number(e); indicates the shape and sublevel
3rd Quantum->Magnetic Quantum Number(m); indicates number/orientation of orbitals around nucleus within subshell
4th Quantum->Spin Quantum Number; indicates the orientation of an electrons magnetic field

Question 27

All electromagnetic radiation, including visible light, can be thought of as
moving________.

Answer 27

waves

Question 28

As the frequency of a wave increases, the wavelength________.

Answer 28

decreases

Question 29

To define the region in which electrons can be found, scientists have assigned four _________ numbers to each electron.

Answer 29

quantum

Question 30

Compare the Rutherford, Bohr, and quantum models of an atom.

Answer 30

Rutherford’s electrons moved in circular orbits, like those of planets. Bohr’s equations gave the regions of space, called orbitals, where the electrons were most likely to be found. The quantum model uses numbers to define the regions in which element.

Question 31

Explain how the wavelengths of light emitted by an atom provide information about electron energy levels.

Answer 31

Electrons release energy to move to lower energy levels. This energy is released as light that has a specific wavelength.

Question 32

In Thomson’s cathode-ray experiment, what evidence led him to believe that the ray consisted of particles, and why did he conclude that they ray was negatively charged?

Answer 32

Thomson believed that the rays were particles because a paddle wheel was set in motion by the ray. He concluded that the beam was negatively charged because the ray came from the negative electrode.

Question 33

Describe the evidence of the existence of electrons.

Answer 33

Thomson’s experiments showed that a cathode ray consist of particles called electrons, that have mass, and a negative charge.

Question 34

Describe the evidence for the existence of protons.

Answer 34

Positively charged particles in the nucleus, called protons, repel alpha particles in the gold-foil experiments.