General Chemistry: Atoms, Periodic Table, Nuclear Chemistry, and Chemical Bonding

Comprehensive practice flashcards covering atoms, the periodic table, nuclear chemistry, radioactivity, and chemical bonding from Chapters 4, 5, and 6.

According to Dalton's atomic theory proposed in $1808$, what happens to atoms during a chemical reaction?

Atoms are rearranged to form new combinations, and they are never created or destroyed during a chemical reaction.

What are the mass and electrical charge of a proton, neutron, and electron in atomic mass units ($\text{amu}$)?

A proton has a charge of $1+$ and a mass of about $1.007\,\text{amu}$; a neutron has a charge of $0$ and a mass of about $1.008\,\text{amu}$; an electron has a charge of $1-$ and a mass of approximately $0.000\,55\,\text{amu}$.

Which four elements make up $96\%$ of total human body mass?

Oxygen ($\text{O}$, $65\%$), carbon ($\text{C}$, $18\%$), hydrogen ($\text{H}$, $9.5\%$), and nitrogen ($\text{N}$, $3.2\%$).

Which elements are classified as macrominerals required by the human body?

Calcium ($\text{Ca}$), phosphorus ($\text{P}$), potassium ($\text{K}$), chlorine ($\text{Cl}$), sulfur ($\text{S}$), sodium ($\text{Na}$), and magnesium ($\text{Mg}$).

What are the common names for Group $1\text{A}\,(1)$, Group $2\text{A}\,(2)$, Group $7\text{A}\,(17)$, and Group $8\text{A}\,(18)$?

Group $1\text{A}$: alkali metals; Group $2\text{A}$: alkaline earth metals; Group $7\text{A}$: halogens; Group $8\text{A}$: noble gases.

Which elements are classified as metalloids along the periodic table's zigzag line?

Boron ($\text{B}$), silicon ($\text{Si}$), germanium ($\text{Ge}$), arsenic ($\text{As}$), antimony ($\text{Sb}$), tellurium ($\text{Te}$), polonium ($\text{Po}$), astatine ($\text{At}$), and tennessine ($\text{Ts}$).

How is the number of neutrons calculated from an atom's mass number ($A$) and atomic number ($Z$)?

$\text{Number of neutrons} = \text{mass number}\,(A) - \text{atomic number}\,(Z)$.

What are isotopes?

Atoms of the same element that have the same atomic number (number of protons) but different mass numbers due to differing numbers of neutrons.

How is the atomic mass of an element calculated from its naturally occurring isotopes?

By multiplying the mass of each isotope by its fractional percent abundance ($\frac{\%\text{ abundance}}{100}$) and summing the resulting contributions.

What wavelength range corresponds to the visible light region of the electromagnetic spectrum?

$400\,\text{nm}$ to $700\,\text{nm}$.

What occurs when an atomic electron moves between principal energy levels ($n$)?

Energy is absorbed when an electron moves to a higher energy level, and energy (light) is emitted when an electron falls to a lower energy level.

What orbital shapes are represented in this diagram?

The top image displays a spherical $s$ orbital, and the bottom image displays a dumbbell-shaped $p$ orbital.

What are the periodic trends for atomic size across a period and down a group?

Atomic size decreases from left to right across a period (due to increased nuclear pull) and increases from top to bottom down a group (due to an increase in energy levels).

What is ionization energy and how does it trend on the periodic table?

The energy required to remove one of the outermost electrons from an atom; it increases from left to right across a period and decreases from top to bottom down a group.

What is metallic character and what are its periodic trends?

The ease with which an element loses valence electrons; it decreases from left to right across a period and increases from top to bottom down a group.

What is an alpha ($\alpha$) particle, and what shielding is sufficient to stop it?

An alpha particle consists of two protons and two neutrons (identical to a helium nucleus, $^4_2\text{He}$); it travels $2\text{ to }4\,\text{cm}$ in air, has a tissue depth of $0.05\,\text{mm}$, and is shielded by paper or clothing.

What is a beta ($\beta$) particle and what shielding is required to protect against it?

A high-energy electron ($^0_{-1}e$) formed when a neutron converts into a proton; it travels $200\text{ to }300\,\text{cm}$ in air, penetrates $4\text{ to }5\,\text{mm}$ of tissue, and requires heavy clothing, lab coats, or gloves for shielding.

What are gamma ($\gamma$) rays and what material is needed to shield against them?

High-energy electromagnetic radiation with no mass or electrical charge emitted from an unstable nucleus; they travel up to $500\,\text{m}$ in air, penetrate $50\,\text{cm}\text{ or more}$ of tissue, and require lead or thick concrete shielding.

Which types of radiation correspond to the penetration depths shown?

$\alpha$ (alpha) particles penetrate only outer skin/clothing; $\beta$ (beta) particles penetrate several millimeters into tissue; $\gamma$ (gamma) rays pass completely through the human body.

What is the common distinction between X-rays and gamma rays based on their source?

X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the atomic nucleus.

What is a radioisotope's half-life ($t_{1/2}$)?

The time required for the radiation level (or quantity of radioactive substance) to decay to one-half of its original value.

If a $36\,\text{mg}$ sample of strontium-90 ($t_{1/2} = 38.1\,\text{years}$) decays for $152.4\,\text{years}$, how much radioactive strontium-90 remains?

$2.25\,\text{mg}$, because $152.4\,\text{years} \div 38.1\,\text{years/half-life} = 4\,\text{half-lives}$, reducing the mass from $36\,\text{mg} \rightarrow 18\,\text{mg} \rightarrow 9\,\text{mg} \rightarrow 4.5\,\text{mg} \rightarrow 2.25\,\text{mg}$.

What radioisotopes are commonly utilized in Positron Emission Tomography (PET)?

Short-lived positron emitters including carbon-11 ($^{11}\text{C}$), oxygen-15 ($^{15}\text{O}$), nitrogen-13 ($^{13}\text{N}$), and fluorine-18 ($^{18}\text{F}$).

How does Magnetic Resonance Imaging (MRI) work and what makes it distinct from CT imaging?

MRI uses strong magnetic fields to excite protons in hydrogen atoms without using X-ray radiation, converting the absorbed radiofrequency energy into detailed images.

What was the name of Raymond Damadian's first MRI prototype and in what year was the first commercial scanner introduced?

The prototype was called "Indomitable" (taking 7 years to complete), and the first commercial MRI scanner was introduced in $1980$ by FONAR.

What is the octet rule in chemical bonding?

Atoms tend to lose, gain, or share valence electrons to achieve a stable arrangement of eight valence electrons, matching the configuration of the nearest noble gas.

How do metals and nonmetals differ in the formation of ions?

Metals have low ionization energies and lose valence electrons to form positively charged cations; nonmetals have high ionization energies and gain valence electrons to form negatively charged anions.

What are the key physical properties of ionic compounds?

They form rigid crystalline solids with high melting and boiling points, are electrical insulators in solid form, and act as electrolytes when dissolved in water.

How are binary ionic compounds named?

The metal cation is written first using its element name, followed by the nonmetal anion formed by taking the first syllable of the element name and adding the suffix -ide.

How are transition metals with variable ionic charges represented in compound names?

A Roman numeral equal to the ionic charge of the metal is placed in parentheses directly following the metal's name (e.g., $\text{Fe}^{3+}$ is iron(III)).

What are polyatomic ions?

A group of covalently bonded atoms that carries an overall positive or negative electrical charge (e.g., $\text{NH}_4^+$ or $\text{SO}_4^{2-}$).

How do the suffixes -ate and -ite distinguish related oxyanions?

The -ate ending denotes the standard, more common oxyanion with more oxygen atoms (e.g., $\text{SO}_4^{2-}$ sulfate), while -ite denotes the related ion with one fewer oxygen atom (e.g., $\text{SO}_3^{2-}$ sulfite).

What prefixes are used for the halogen oxyanions of chlorine ($\text{ClO}_4^-$, $\text{ClO}_3^-$, $\text{ClO}_2^-$, and $\text{ClO}^-$)?

$\text{ClO}_4^-$ is perchlorate (one more oxygen than chlorate), $\text{ClO}_3^-$ is chlorate, $\text{ClO}_2^-$ is chlorite (one less oxygen than chlorate), and $\text{ClO}^-$ is hypochlorite (lowest oxidation state).

What rule governs the naming of molecular compounds composed of two nonmetals?

The first nonmetal is named by its full element name, the second is named with the suffix -ide, and Greek prefixes (mono-, di-, tri-, tetra-, penta-, etc.) indicate the number of each atom present.

What electronegativity difference ranges define nonpolar covalent, polar covalent, and ionic bonds?

An electronegativity difference of $0.0\text{ to }0.4$ indicates a nonpolar covalent bond; $0.5\text{ to }1.8$ indicates a polar covalent bond; greater than $1.8$ indicates an ionic bond.

According to VSEPR theory, what are the electron geometry, molecular shape, and bond angle of methane ($\text{CH}_4$)?

Tetrahedral electron-group geometry, tetrahedral molecular shape, and a bond angle of $109^\circ$.

Why is water ($\text{H}_2\text{O}$) classified as a polar bent molecule with a bond angle of $104.5^\circ$?

Oxygen has four electron groups (two single bonds and two lone pairs); the repulsion from the two lone pairs reduces the tetrahedral angle ($109.5^\circ$) to $104.5^\circ$, and the individual bond dipoles do not cancel.

Why is carbon tetrachloride ($\text{CCl}_4$) a nonpolar molecule despite having polar bonds?

The four polar $\text{C}-\text{Cl}$ bond dipoles point symmetrically toward the corners of a tetrahedron, completely canceling each other out.

What conditions are necessary for hydrogen bonding to occur between molecules?

A hydrogen atom must be covalently bonded to a highly electronegative atom ($\text{F}$, $\text{O}$, or $\text{N}$) and attracted to an unshared electron pair on another $\text{F}$, $\text{O}$, or $\text{N}$ atom.

Rank the relative strengths of ionic bonds, hydrogen bonds, dipole–dipole attractions, and dispersion forces.

Ionic bonds are the strongest, followed by hydrogen bonds, then dipole–dipole attractions, and dispersion forces are the weakest.