The electron has a negative charge of approximately −1.6 × 10⁻¹⁹ coulombs, as determined by experiments like Millikan’s oil drop experiment.

The proton’s mass is approximately 1.67 × 10⁻²⁷ kg, about 1836 times heavier than an electron.

The nucleus contains protons (positive charge) and neutrons (neutral), while electrons orbit outside.

Carbon-12 has an atomic number of 6, meaning it has 6 protons.

Isotopes have the same number of protons but different numbers of neutrons, affecting mass number.

The L shell (n=2) can hold a maximum of 2n² = 2(2²) = 8 electrons.

The p-subshell (ℓ=1) has 2ℓ+1 = 2(1)+1 = 3 orbitals (px, py, pz).

Orbitals are defined by principal (n), azimuthal (ℓ), and magnetic (m) quantum numbers. Spin (s) describes electron spin, not the orbital.

The azimuthal quantum number (ℓ) defines orbital shape: ℓ=2 corresponds to d orbitals.

Radial nodes = n − ℓ − 1. For 3s, n=3, ℓ=0, so nodes = 3 − 0 − 1 = 2.

Bohr’s model works for hydrogen-like atoms but fails for multi-electron atoms like helium due to electron interactions.

In Bohr’s model, electron velocity in the first orbit (n=1) of hydrogen is approximately 2.2 × 10⁶ m/s.

Photon energy is E = hf (or E = hν), where h is Planck’s constant and f (or ν) is frequency.

Heisenberg’s principle states that position and momentum cannot be measured simultaneously with arbitrary precision.

Orbital angular momentum is quantized as √(ℓ(ℓ+1))ℏ, where ℓ is the azimuthal quantum number and ℏ is reduced Planck’s constant.

The Aufbau principle states that electrons fill orbitals in order of increasing energy (e.g., 1s, 2s, 2p, etc.).

Oxygen (atomic number 8) has 8 electrons: 1s² 2s² 2p⁴ in its ground state.

s orbitals (ℓ=0) are spherical, while p, d, and f orbitals have directional shapes.

The magnetic quantum number (m) specifies the orientation of an orbital in space (e.g., px, py, pz for p orbitals).

The spin quantum number (s) for an electron is either +½ or −½, representing two possible spin states.