Electrons and Spectra

Why do electrons occupy the electron cloud instead of a fixed orbit?

Electrons exist in regions of probability, moving fast, spinning, repelling each other, and attracted to the nucleus, forming the electron cloud.

How does the size of the electron cloud compare to the nucleus?

The electron cloud is much larger than the tiny, dense nucleus, though electrons are nearly weightless.

What does the nucleus contain and what is its role?

The nucleus contains protons and neutrons, providing most mass and a positive charge attracting electrons.

How does electron behavior influence atomic structure?

Electrons repel each other and are attracted to the nucleus, creating a structured cloud with shells and subshells.

How are electron shells organized?

Shells (1–7) are energy levels around the nucleus, each holding a max number of electrons: 1:2, 2:8, 3:18, 4:32, 5:32.

Why do electrons fill inner shells before outer shells?

Inner shells are closer to the nucleus and lower in energy, so electrons occupy them first (Aufbau principle).

What are subshells and their types?

Subshells divide shells into s (2e⁻), p (6e⁻), d (10e⁻), f (14e⁻), each containing orbitals where electrons reside.

How many orbitals and electrons can an s subshell hold?

1 orbital, 2 electrons (spinning opposite directions).

How many orbitals and electrons can a p subshell hold?

3 orbitals, 6 electrons max.

How many orbitals and electrons can a d subshell hold?

5 orbitals, 10 electrons max.

How many orbitals and electrons can an f subshell hold?

7 orbitals, 14 electrons max.

Why do electrons spin in opposite directions in an orbital?

To satisfy the Pauli Exclusion Principle: each orbital holds max 2 electrons with opposite spins.

What is the rule for writing electron configurations?

Start from lowest energy (1s), fill subshells in order, account for overlap, and stop at the element’s atomic number.

How do you write configuration notation?

Use n (shell number), subshell letter (s,p,d,f), and superscript for electron count, adjusting n for d (n-1) and f (n-2).

What is a noble gas shortcut in configurations?

Use the preceding noble gas in brackets to represent inner electrons, then add remaining electrons.

Example: Fluorine configuration?

1s² 2s² 2p⁵; 2 electrons in first shell, 7 in outer, showing valence electrons.

Why do energy level overlaps affect transition metals?

Higher energy shells branch, causing s and d orbitals to overlap, changing filling order.

What do orbital diagrams show?

Each orbital as a line, electrons as arrows (opposite spins pair up), showing electron distribution in subshells.

How does Hund’s Rule apply to orbital diagrams?

Electrons fill degenerate orbitals singly before pairing to minimize repulsion.

How does Pauli Exclusion Principle apply?

Each orbital holds max 2 electrons with opposite spins.

How does the Aufbau Principle guide filling?

Electrons occupy lowest energy orbitals first (1s → 2s → 2p …).

Nitrogen orbital diagram significance?

1s² 2s² 2p³; each 2p orbital has 1 electron first (Hund’s Rule) before pairing.

What are valence electrons?

Outermost electrons in the highest energy shell; determine chemical bonding and reactivity.

How do alkali metals demonstrate valence patterns?

Each has 1 valence electron in outermost shell; configuration ends in s¹.

How do halogens demonstrate valence patterns?

Each has 7 valence electrons; highly reactive due to needing 1 more for full shell.

How are Lewis dot diagrams constructed?

Place dots representing valence electrons around the element symbol, pair as needed, showing bonding/lone pairs.

Why are electrons spaced apart in Lewis diagrams?

Electron repulsion requires spacing; paired electrons spin oppositely for stability.

What is ground state of an atom?

Lowest energy arrangement of electrons; standard electron configuration.

What is excited state?

Electrons temporarily occupy higher energy orbitals after absorbing energy.

What is a quantum leap?

Electron jumps between energy levels, absorbing or emitting energy.

How do fireworks demonstrate electron transitions?

Electrons absorb energy, jump levels, then release energy as colored light when returning to ground state.

How is electromagnetic radiation related to electron transitions?

Energy released during transitions emits light; wavelength and energy vary across spectrum (gamma → radio).

Bohr model explanation of energy absorption/release?

Electrons absorb energy → excited → unstable → return to ground state → emit light (conserving energy).

Lyman Series: which transition & radiation?

To level 1, emits ultraviolet light (purple), observed in hydrogen spectrum.

Balmer Series: which transition & radiation?

To level 2, emits visible light (blue/red).

Paschen Series: which transition & radiation?

To level 3, emits infrared light (red).

How do electron transitions explain spectral lines?

Each series corresponds to electrons dropping to a specific energy level, emitting photons of specific wavelength.

Fundamental wave equation for light?

c = λν; speed of light = wavelength × frequency.

How is wavelength related to energy?

Shorter wavelength → higher energy; longer wavelength → lower energy.

How is the periodic table organized by electron structure?

Into s, p, d, f blocks corresponding to subshell types; reflects electron configurations and properties.

Which groups correspond to s-block?

Groups 1-2; outer electrons in s subshell.

Which groups correspond to p-block?

Groups 13-18; outer electrons in p subshell.

Which groups correspond to d-block?

Transition metals; outer electrons fill d subshells.

Which groups correspond to f-block?

Lanthanides and actinides; electrons fill f subshells.