General Chemistry Fundamentals and Periodic Trends

Comprehensive practice flashcards covering basic atomic theory, chemistry experiments, periodic trends, quantum mechanics, and molecular bonding as described in the lecture notes.

What is the definition of an atom according to the lecture notes?

The smallest part of something that cannot be broken down chemically; for example, iron ($Fe$).

How is a molecule defined?

A group of one or more atoms that are bonded together.

What is a compound?

A substance made up of two or more atoms of different elements; for example, Salt ($NaCl$).

Explain the significance of JJ Thomson's Cathode Ray Tube experiment.

Thomson discovered the electron by observing that ejected particles bent toward a positive current, proving Dalton's theory that all atoms are indivisible and indestructible is FALSE.

What were the conclusions of Ernest Rutherford's Gold Foil Experiment?

He discovered the atom is mostly empty space with a positively charged, dense area in the center now known as the nucleus.

What are the four fundamental forces identified in the notes?

$$1. ext{Gravitational, } 2. ext{Electrostatic, } 3. ext{Strong Forces, and } 4. ext{Weak Forces.}$$

Why are gravitational forces not significant at the atomic/molecular level?

They are too weak to be detected; for example, the gravitational force between a proton and an electron is non-existent.

Describe the relationship between distance and force described in the lecture.

As the distance between two objects increases, the force decreases; as the distance decreases, the force increases.

What is the First Law of Thermodynamics?

Energy is NEVER lost; it can be transferred or transformed.

How do potential energy and kinetic energy change when a ball is dropped?

As the ball falls, its potential energy decreases and its kinetic energy increases because the ball is in motion.

What are the characteristics of an Absorption Spectrum?

It shows dark lines where light was absorbed, and energy transitions are represented by upwards arrows indicating a gain in energy.

What are the characteristics of an Emission Spectrum?

It shows colored lines where light was emitted, and energy transitions are represented by downwards arrows indicating a loss of energy.

What experiment proved that light behaves as a wave?

The double slit experiment, which showed constructive and destructive interference patterns.

What is the threshold frequency in the context of the photoelectric effect?

The certain frequency above which electrons are emitted from a metal regardless of intensity; if light is below this frequency, no electrons are emitted.

What are the two requirements for electrons to be emitted via the photoelectric effect?

$$1. ext{Photons must be above the threshold frequency, and } 2. ext{photons must have enough energy to overcome the attractive forces between the nucleus and the electrons.}$$

State the de Broglie equation used to calculate wavelength ($ext{\lambda}$).

\lambda = rac{h}{m imes V}, where $h$ is Planck's constant ($6.626 \times 10^{-34}\, ext{J}\cdot ext{s}$), $m$ is mass, and $V$ is velocity.

How does Atomic Radius change on the Periodic Table?

Atomic radius DECREASES across a period (left to right) and INCREASES down a group.

What is Effective Nuclear Charge ($Z_{eff}$) and what is its periodic trend?

$Z_{eff}$ is the actual nuclear charge minus the charge screened by core electrons ($Z_{eff} = Z - S$); it INCREASES across a period and DECREASES down a group.

Define Ionization Energy.

The energy required to move an electron from an atom during the gas phase.

What is Heisenberg's Uncertainty Principle?

We cannot know both an electron's exact position and its energy simultaneously.

Describe the Aufbau Principle.

Electrons occupy the lowest energy level orbitals first.

Describe Hund's Rule.

Electrons occupy orbitals of the same energy singly and do not pair up unless they have to.

What are the differences between core and valence electrons?

Core electrons are low in energy, close to the nucleus, and very stable; valence electrons are higher in energy, outside the closed shell, and determine reactivity.

What is the trend for Electronegativity on the periodic table?

It increases across a period and decreases down a group (excluding noble gases), with Fluorine having the highest value.

What are London Dispersion Forces (LDFs)?

Weak attractions present between all molecules caused by induced dipoles; they get stronger as more electrons are added or as the electron cloud size increases.

Define Hybridization in the context of Valence Bond Theory.

The combination of atomic orbitals (such as $s$ and $p$) to form hybrid orbitals (such as $sp, sp^2, ext{ or } sp^3$) when atoms overlap to form localized bonds.

According to Molecular Orbital Theory, what is the impact of electrons in bonding versus antibonding orbitals?

Electrons in bonding orbitals make the species more stable (stabilizing), while electrons in antibonding orbitals make the species less stable (destabilizing).

What is the formula for calculating Bond Order?

ext{Bond Order} = rac{1}{2}( ext{bonding electrons} - ext{antibonding electrons}).

What characterizes a Sigma (\text{\sigma}) bond versus a Pi (\text{\pi}) bond?

A sigma bond results from the direct overlap of orbitals and can rotate; a pi bond results from the side-by-side overlap of $p$ orbitals and cannot rotate.

What is the formal charge formula?

ext{Formal Charge} = ( ext{Valence electrons}) - [rac{1}{2}( ext{bonding electrons})] - ( ext{electrons in lone pairs}).

In VSEPR theory, what are the geometry and bond angle for a central atom with 2 regions of electron density and 0 lone pairs?

The hybridization is $sp$, the electron and molecular shape are both linear, and the bond angle is $180^ ext{o}$.

In VSEPR theory, what are the geometry and bond angle for a central atom with 4 regions of electron density and 0 lone pairs?

The hybridization is $sp^3$, the electron and molecular shape are both tetrahedral, and the bond angle is $109.5^ ext{o}$.

How does the strength of an IMF correspond to melting and boiling points?

The stronger the Intermolecular Force (IMF), the higher the melting and boiling points will be.

Why does graphite conduct electricity while diamond does not?

In diamond, electrons are localized; in graphite, electrons move more freely because the pi orbitals form a network.