2A1 Atomic and Nuclear Structure and Processes

Question 1

Define:

Atom

Answer 1

The smallest unit of matter.

Atoms are the basic building blocks of all elements and compounds.

Question 2

Which three subatomic particles make up an atom?

Answer 2

• Protons
• Neutrons
• Electrons

Protons and neutrons are located in the nucleus, while electrons orbit around the nucleus.

Question 3

What is the charge of a proton?

Answer 3

Positive (+)

Protons carry a positive electrical charge, opposite to the negative charge of electrons.

Question 4

Where are protons located in an atom?

Answer 4

In the nucleus.

Protons, along with neutrons, make up the nucleus of an atom, contributing most of the atom’s mass.

Question 5

Where are electrons located in an atom?

Answer 5

Outside the nucleus, in electron shells.

Electrons move around the nucleus in specific energy levels or orbitals.

Question 6

Fill in the blank:

The atomic number of an element is the number of ________.

Answer 6

protons

(Photo credit: BYJU's)

The atomic number determines the identity of an element, as all atoms of a given element have the same number of protons.

Question 7

Fill in the blank:

The mass number of an atom is represented by the letter _____.

Answer 7

A

The mass number is the sum of protons and neutrons and is represented by the letter A in element notation.

Question 8

Fill in the blank:

Mass number = ________ + ________.

Answer 8

Protons, Neutrons

The mass number is the sum of protons and neutrons and is often represented by the symbol “A”.

Question 9

Define:

Isotope

Answer 9

Atoms of the same element with different numbers of neutrons.

Isotopes have the same chemical properties but differ in mass due to the varying number of neutrons. Examples include Carbon-12 or Hydrogen-2.

Question 10

What is the difference between an isotope and an ion?

Answer 10

Isotopes differ in neutrons, while ions differ in electrons.

Isotopes are atoms of the same element with different numbers of neutrons; ions are atoms with a net charge due to the loss or gain of electrons.

Question 11

True or False:

An element is a substance made up of only one type of atom.

Answer 11

True

Elements are pure substances consisting of atoms with the same number of protons. Examples include oxygen or carbon.

Question 12

True or False:

Mass number and atomic mass are the same.

Answer 12

False

Mass number is the total of protons and neutrons in a nucleus, while atomic mass is the weighted average of all naturally occurring isotopes.

Question 13

Who discovered the nucleus of the atom in 1909?

Answer 13

Ernest Rutherford

Rutherford’s gold foil experiment revealed that atoms have a dense central nucleus.

Question 14

What is the mass of an electron?

Answer 14

Nearly 0 atomic mass units.

Electrons are so light compared to protons and neutrons that their mass is considered negligible in most calculations.

Question 15

Define:

atomic orbitals

Answer 15

Regions around the nucleus where electrons are likely to be found.

Orbitals are located at discrete distances from the nucleus.

Electrons closer to the nucleus have lower energy.

Question 16

True or False:

The periodic table organizes elements based on atomic mass.

Answer 16

False

Elements are arranged by atomic number, not mass, in the periodic table, showing trends in their properties.

Question 17

Describe the Bohr model of the atom.

Answer 17

It shows an atom as a central nucleus containing protons and neutrons with the electrons in circular orbits around the nucleus at fixed energy levels.

(Photo credit: PNGWing)

It explains atomic spectra but is limited for complex atoms.

Question 18

Fill in the blank:

The ground state energy for the hydrogen atom is _______.

Answer 18

-13.6 eV

The ground state energy is the lowest energy level of an electron in a hydrogen atom. This value, -13.6 eV, represents the energy required to remove the electron from the atom (ionization energy) when it is in its most stable state.

Question 19

What describes the arrangement of electrons in an atom’s electron shells?

Answer 19

Electron configuration

Electron configuration indicates how electrons are distributed in an atom’s orbitals, influencing its chemical behavior and bonding. Examples include configurations like 1s² 2s² 2p⁶.

Question 20

What is the electron configuration for hydrogen?

Answer 20

1s¹

Hydrogen has one electron, which occupies the 1s orbital.

Question 21

What type of radiation is emitted when an electron transitions from a higher energy state to a lower energy state?

Answer 21

Electromagnetic radiation (light).

This release of energy is typically observed as visible light or photons, depending on the energy difference.

Question 22

True or False:

Valence electrons are the outermost electrons that determine an atom’s reactivity.

Answer 22

True

These electrons are key in determining an atom’s chemical reactivity and bonding behavior.

Question 23

True or False:

Hund’s Rule states that electrons in subshells must pair up in orbitals before occupying separate orbitals.

Answer 23

False

Hund’s Rule states that electrons occupy separate orbitals in a subshell before pairing up to minimize electron-electron repulsion.

Question 24

What is an electron shell?

Answer 24

An electron shell is the space around the nucleus in which an electron can be found.

(Photo credit: PNG Wing)

Electron shells represent areas where electrons are most likely to be located and are numbered based on their distance from the nucleus.

Question 25

What is the **order** of filling electron shells?

Answer 25

1s, 2s, 2p, 3s, 3p, 4s, 4d, 4p, ... ## Footnote This order follows the **Aufbau principle**, where electrons fill orbitals from lowest to highest energy.

Question 26

What is the **Aufbau Principle**?

Answer 26

**Electrons** fill lower energy levels before higher ones. ## Footnote This [principle](https://study.com/academy/lesson/the-aufbau-principle.html#:~:text=The%20Aufbau%20Principle%20states%20that,subshell%20begins%20to%20fill%20in.) explains why 1s is filled before 2s, and 2s before 2p.

Question 27

What are the possible **subshells** an electron can occupy?

Answer 27

s, p, d, f ## Footnote Each subshell has a specific number of orbitals: s (1 orbital), p (3 orbitals), d (5 orbitals), and f (7 orbitals).

Question 28

# True or False: When an electron moves from n = 2 to n = 3, it **releases** energy.

Answer 28

False ## Footnote When an electron transitions to a higher energy level (n = 3), it **absorbs** energy, not releases it.

Question 29

What happens when an electron **absorbs** energy?

Answer 29

It **moves** to a higher energy level. ## Footnote Absorbing energy causes the electron to jump from its ground state to an excited state, where it may later release energy.

Question 30

What are the four **quantum numbers** used to describe an electron?

Answer 30

* n * l * ml * ms ## Footnote Each quantum number describes a specific property of an electron's state: principal quantum number (n), angular quantum number (l), magnetic quantum number (ml), and spin quantum number (ms).

Question 31

What is the **maximum** number of electrons that can occupy an s sublevel?

Answer 31

2 ## Footnote The *s sublevel* consists of one orbital, which can hold **two electrons** with opposite spins.

Question 32

What are the possible **spin states** of an electron?

Answer 32

+1/2 or -1/2 ## Footnote Electrons must have opposite spins when occupying the same orbital, as dictated by the Pauli Exclusion Principle.

Question 33

What does the quantum number “n” **represent** in an electron's state?

Answer 33

The principal energy level. ## Footnote The principal quantum number (n) indicates the distance of an electron from the nucleus and its energy level, with higher values of n corresponding to higher energy levels.

Question 34

What is **shorthand** electron configuration?

Answer 34

Using the **previous** row’s noble gas as a starting point. ## Footnote This method **simplifies** electron configuration by referencing the nearest noble gas to reduce repetition.

Question 35

What is an **absorption spectrum**?

Answer 35

A spectrum showing absorbed **wavelengths** of light. ## Footnote It appears as dark lines where light is absorbed by atoms or molecules.

Question 36

What is an **emission spectrum**?

Answer 36

A spectrum showing **light** emitted by atoms or molecules. ## Footnote It appears as bright lines at specific wavelengths.

Question 37

What determines the **color of light emitted** by an atom?

Answer 37

The **energy difference** between two electronic levels. ## Footnote Larger energy gaps produce shorter wavelengths. The specific wavelengths correspond to different colors in the visible spectrum.

Question 38

Explain why **visible spectra** are limited to certain colors.

Answer 38

Only **specific wavelengths** correspond to energy differences in visible transitions. ## Footnote Visible transitions occur in the range of *400* to *700* nm.

Question 39

# True or False: Absorption spectra **identify** unknown substances.

Answer 39

True ## Footnote Comparing absorption patterns reveals unknown compounds.

Question 40

# Define: radioactive decay

Answer 40

A **spontaneous process** where unstable nuclei emit radiation to become stable. ## Footnote This process continues until a stable nucleus is formed. It can involve a change in the number of protons and/or neutrons.

Question 41

When is a nucleus considered **unstable**?

Answer 41

When nuclear forces **cannot overcome electrostatic repulsive forces** between protons. ## Footnote An unstable nucleus undergoes a change that releases energy in the form of a particle or ionizing radiation. Stability depends on the ratio of neutrons to protons (n/p).

Question 42

List the *three* major **types of radioactive decay**.

Answer 42

1. Alpha decay 1. Beta decay 1. Gamma decay ## Footnote Neutron radiation is also another type.

Question 43

What are **beta particles**?

Answer 43

**High-speed electrons or positrons** released in a beta decay. ## Footnote These particles are produced when a proton is broken into a smaller particle. They have moderate penetration power, but can be stopped by aluminum.

Question 44

When does an **alpha decay** occur?

Answer 44

When a nucleus with **too many protons** emits an alpha particle (α).

Question 45

# Define: alpha particles

Answer 45

They consist of **two protons and two neutrons** released during alpha decay. ## Footnote Alpha particles are equivalent to helium nuclei. They tend to be heavy and positively charged, but have low penetration power. They can be stopped by something as thin as a sheet of paper!

Question 46

# Define: gamma decay

Answer 46

It is the release of **high-energy photons** from an unstable nucleus without changing its composition. ## Footnote Gamma rays are electromagnetic waves with high energy but no mass. They can be dangerous to humans and can be stopped by thick lead.

Question 47

# Define: beta decay

Answer 47

A type of radioactive decay where a radioisotope **emits a beta particle (β),** equivalent to an electron. ## Footnote It increases or decresases the atomic number of a radioisotope by *one*, but does not change the mass.

Question 48

Compare the **penetration power** of alpha, beta, and gamma radiation.

Answer 48

* Alpha: **low**, stopped by paper * Beta: **moderate**, stopped by aluminum * Gamma: **high**, stopped by thick lead ## Footnote The penetration depends on the type of radiation and can determine the level of danger of that kind of radiation to humans. Gamma rays can penetrate and ionize tissues, create free radicals, and cause cancers.

Question 49

What is **nuclear notation**?

Answer 49

A way to **denote changes in the nuclear structure** using the elemental symbol, atomic number, and atomic mass. ## Footnote Example: Uranium can be written as 238/92 U.

Question 50

# Define: half-life

Answer 50

The amount of time it takes for **half of the nucleus of an element to break down**. ## Footnote It is a measure of the rate at which radioactive decay occurs. It can range from seconds to years.

Question 51

How do you calculate the **number of half-lives** that have passed?

Answer 51

n = t / T ## Footnote Where t is the time that has passed and T is the length of the half-life.

Question 52

What **type of graph** represents radioactive decay?

Answer 52

An **exponential** decay graph. ## Footnote The graph is exponential because the decay function involves raising a fraction (1/2) to the power of the number of half-lives elapsed. The y-value decreases and approaches zero as the x-value increases.

Question 53

How can you determine **half-lives from a decay graph**?

Answer 53

By finding the **x-value corresponding to the y-value that is half of the initial** amount. ## Footnote For example, if the initial y-value is *15* g, half-life corresponds to *7.5* g on the y-axis.

Question 54

# True or False: All elements undergo radioactive decay **at the same rate**.

Answer 54

False ## Footnote Decay rates vary depending on the isotope's half-life.

Question 55

# Define: nuclear **fission**

Answer 55

A large nucleus **splits** into two or more smaller nuclei. ## Footnote To create this kind of reaction, unstable heavy atoms are hit with neutrons. The additional neutrons lead to more instability, which then leads to the split of the nucleus into smaller atoms or neutrons.

Question 56

# Define: nuclear **fusion**

Answer 56

Two light nuclei **combine** to form a heavier nuclei. ## Footnote When this happens, the final resultant atom is lighter than the two individual pieces. Since mass was lost in the reaction, a large amount of energy is released.

Question 57

What is a **nuclear reaction**?

Answer 57

A process involving the **transformation of atomic nuclei**.

Question 58

What is the **difference** between nuclear fusion from nuclear fission?

Answer 58

* Fusion: **two light nuclei combine** to form a heavier nucleus. * Fission: **large nucleus splits** into two or more smaller nuclei. ## Footnote One reaction represents the combination of nuclei, while the other represents the split of a large nuclei. Both produce energy, but we are only able to easily harness the energy created from fission.

Question 59

# Fill in the blanks: In nuclear fission, a heavy **nucleus splits into** \_\_\_\_\_\_\_\_ and \_\_\_\_\_\_\_.

Answer 59

smaller nuclei; neutrons ## Footnote Energy is also released in the process. This process is the basis for nuclear power generation.

Question 60

# Define: nuclear equations

Answer 60

Symbolic **representations of nuclear reactions** written with reactants and products separated by an arrow. ## Footnote Example format: Reactants ⟶ Products.

Question 61

# Define: nuclear chemistry

Answer 61

A field of chemistry that deals with the **use of radioactive isotopes** and other nuclear reactions. ## Footnote It is used in daily our lives for: * Diagnosing diseases * Treating medical conditions * Determining the age of artifacts * Energy production

Question 62

What is a **radioactive tracer**?

Answer 62

A radioactive isotope used to **track chemical pathways** or **locate abnormalities** in the body. ## Footnote Stable atoms in the body are replaced by radioactive atoms, which help in diagnosing diseases.

Question 63

# Define: carbon dating

Answer 63

A method that uses the **decay of carbon-14** to determine the age of artifacts. ## Footnote It relies on measuring the ratio of carbon-14 to carbon-12 in once-living materials. The half-life of carbon-14 is approximately *5,730 years*. Every 5,730 years, half of the carbon-14 in an artifact decays into nitrogen through a beta decay.

Question 64

How is gamma decay used in the **medical field**?

Answer 64

* Radiation therapy for cancer * Sterilizing equipment * Diagnostic imaging tracers ## Footnote Gamma rays can pass through human tissue, which allows for diagnostics and therapeutic uses. However, they must be used carefully because they have the potential to damage human tissue and DNA.