Unit 2: Light, Electron Configurations, and Periodic Trends

Comprehensive practice flashcards covering wave mechanics, light emission, electron configurations, orbital diagrams, valence electrons, ions, chemical formulas, and periodic trends.

According to nuclear atom discoveries, what causes atoms to emit light and other electromagnetic radiation?

The wiggling of electrons inside the atom.

What is the definition of electromagnetic radiation?

A form of energy that exhibits wavelike behavior as it travels through space (e.g., visible light, microwaves, X-rays, radio waves).

How is wavelength ($\lambda$) defined, and what is its relationship to wave frequency?

Wavelength is the shortest distance between two points on a continuous wave (crest to crest or trough to trough). Shorter wavelengths have higher frequency, while longer wavelengths have lower frequency.

What is wave amplitude?

A wave's height measured from the middle (origin) to the crest or trough.

What occurs to metal electrons during a flame test to produce characteristic colors?

Heating causes electrons to become excited and jump to higher energy levels. When they fall back down, they emit energy as visible light of a color unique to that metal.

What is the ground state electron configuration of an atom?

The most stable arrangement of electrons in an atom.

What is the difference between electron configuration notation and an orbital diagram?

Electron configuration notation is a written representation of electron locations around the nucleus, whereas an orbital diagram is a visual representation of electrons within atomic orbitals.

What is the hierarchical organization of electrons within an atom from largest to smallest division?

Energy Level $\rightarrow$ Sublevel $\rightarrow$ Orbital $\rightarrow$ Electron.

What is the maximum number of electrons permitted in the principal energy levels $n = 1$, $n = 2$, $n = 3$, and $n = 4$?

• $n = 1$ (K-shell): $2$ electrons
• $n = 2$ (L-shell): $8$ electrons
• $n = 3$ (M-shell): $18$ electrons
• $n = 4$ (N-shell): $32$ electrons

How many orbitals and maximum electrons are present in the $s$, $p$, $d$, and $f$ sublevel blocks?

• $s$ block: $1$ orbital, $2$ electrons
• $p$ block: $3$ orbitals, $6$ electrons
• $d$ block: $5$ orbitals, $10$ electrons
• $f$ block: $7$ orbitals, $14$ electrons

What is the Aufbau Principle?

A principle stating that each electron occupies the lowest energy orbital available before higher energy orbitals are filled (electrons must fill in order and cannot bounce around).

What is the Pauli Exclusion Principle?

A principle stating that a maximum of $2$ electrons can occupy a single atomic orbital, but only if they have opposite spins, which cancels out their magnetic momentum.

What is Hund's Rule?

A rule stating that single electrons with the same spin must occupy each equal-energy orbital before additional electrons with opposite spins can pair up in the same orbital.

What three core rules govern the creation of orbital diagrams?

1) The lowest energy orbitals are filled before higher energy orbitals (Aufbau Principle). 2) Each orbital receives one electron first before a second is added (Hund's Rule). 3) Only $2$ electrons of opposite spins can occupy each orbital (Pauli Exclusion Principle).

How is the noble gas shortcut method written for an electron configuration?

Identify the noble gas in the period above the element, place its symbol in brackets ($[\text{Noble Gas}]$), and write the remaining configuration that follows.

What are the regular and noble gas electron configurations for Sodium ($Na$, atomic # $11$)?

Regular: $1s^2 2s^2 2p^6 3s^1$ Noble Gas: $[\text{Ne}]\,3s^1$

What are valence electrons?

The number of electrons located in the outermost ring (energy level) of an atom.

Why do elements in the same group on the periodic table display similar chemical properties?

They contain the same number of valence electrons.

What does the energy level of an element's valence electrons indicate about its placement on the periodic table?

It indicates the period (row) on the periodic table in which the element is located.

What are the exceptions to the periodic table group number rule for valence electrons?

The group number rule applies only to s- and p-block elements, and Helium is an exception because it contains only $2$ valence electrons.

What are the scientific definitions of an atom, a molecule, a compound, and an ion?

• Atom: A single element unit (e.g., $Na$)
• Molecule: Two or more elements chemically bonded together (e.g., $H_2$)
• Compound: Two or more different elements chemically bonded together (e.g., $H_2O$)
• Ion: An atom or molecule with an electrical charge

How many total atoms of each element are present in $3Al_2(SO_4)_3$?

$6$ Aluminum ($Al$), $9$ Sulfur ($S$), and $36$ Oxygen ($O$) atoms.

Which seven elements form diatomic molecules in their standard state?

$N_2$, $O_2$, $F_2$, $Cl_2$, $Br_2$, $I_2$, and $H_2$ (remembered as "7up").

How do anions and cations form, and what are their respective charges?

An anion has a negative charge ($-$) and forms when electrons are added to a neutral atom. A cation has a positive charge ($+$) and forms when electrons are lost (subtracted) from a neutral atom.

What are the steps for writing an ionic formula using oxidation numbers?

1) Write the symbols and oxidation numbers of the metal cation ($+\text{charge}$) and nonmetal anion ($-\text{charge}$). 2) Reduce the oxidation numbers if possible. 3) Criss-cross the numbers to form subscripts and drop the signs.

What is the correct chemical formula formed between Silicon ($Si^{4+}$) and Sulfur ($S^{2-}$)?

$SiS_2$ (the oxidation numbers reduce from $4+:2-$ to $2+:1-$ before criss-crossing).

What is atomic radius, and what are its periodic trends across a period and down a group?

Atomic radius is the distance from the nucleus to the outer edge of the electron cloud. It decreases across a period (more protons pull electrons closer) and increases down a group (new electron shells increase distance).

What is electronegativity, and why do noble gases have an electronegativity value of zero?

Electronegativity indicates the relative ability of an atom to attract electrons. Noble gases have zero electronegativity because their outer electron shell is completely filled to the maximum, making them stable.

What is ionization energy (IE), and how does it correlate with atomic size and electronegativity?

Ionization energy is the energy required to remove an electron. A smaller atomic size increases nuclear attraction, leading to higher electronegativity and higher ionization energy ($\downarrow \text{size} = \uparrow \text{electronegativity} = \uparrow \text{IE}$).