Honors Chemistry I: Unit 2 - Quiz 3

Atom

Smallest particle of matter; from Greek atomos, "indivisible"

Democritus

Ancient Greek thinker (about 400 BCE) who first proposed that matter is made of indivisible atoms

Antoine Lavoisier

Scientist (mid-1700s) who stated the Law of Conservation of Mass by weighing reactants and products

Law of Conservation of Mass

Mass can neither be created nor destroyed

Nucleus

Small, dense, positively charged center of the atom; holds protons and neutrons and about 99.9% of the atom's mass

Electron

Negatively charged subatomic particle found outside the nucleus

Nuclear (planetary) model

Early 1900s model with a dense positive nucleus and electrons outside it; most of the atom's volume is empty space

Emission spectrum

Characteristic set of light frequencies an element gives off when it gains energy (electricity or heat)

Why isn't a full rainbow formed in an emission spectrum?

Only certain frequencies of light are emitted, each matching a specific energy amount

Electromagnetic spectrum

The full range of electromagnetic radiation; visible light is only a small part

Order of the electromagnetic spectrum (long to short wavelength)

Radio, microwaves, infrared, visible, ultraviolet, X-rays, gamma rays

Visible light range

About 400 nm (violet) to 700 nm (red)

Wavelength (λ)

Distance between identical points on a wave, measured in m or nm

Frequency (ν)

Number of times a wave passes a point per unit time, measured in Hz (s⁻¹)

Amplitude

Height of a wave; related to intensity/brightness

Hertz (Hz)

Unit of frequency; equal to s⁻¹

Speed of light (c)

3.0 × 10⁸ m/s

c = λν

Relates wavelength and frequency; they are inversely related

E = hν

Relates energy and frequency; they are directly related

Planck's constant (h)

6.63 × 10⁻³⁴ J/Hz

Long wavelength light

Low frequency and low energy

Short wavelength light

High frequency and high energy

Bohr model of the atom

Model in which electrons exist only at fixed energy levels (n) around the nucleus

Energy level (n)

A fixed energy state an electron can occupy in Bohr's model

Quantum leap

Electron movement between energy levels; electrons cannot exist between levels

Quantum / photon

The specific amount of energy needed to move an electron between levels

Absorption (Bohr model)

Atom absorbs a specific amount of energy and the electron jumps to a higher level

Emission (Bohr model)

Electron falls back to a lower level and the atom releases that specific energy as EMR

EMR

Electromagnetic radiation; if in the visible range, we can see it

ΔE

Energy difference between two levels; equals the energy of the emitted photon

Ionization (Bohr diagram)

Top of the energy diagram (n = ∞), where the electron is removed from the atom

Steps to find the color of light emitted in a Bohr transition

Find ΔE, use E = hν to get ν, use c = λν to get λ, then match λ to the spectrum

2 Meanings of ΔE

1. How much energy is needed to jump UP the electron or 2. how much energy the electron releases when it FALLS

Per second or /s is otherwise known as...

Hertz (Hz)