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chem 142
| Question | Answer |
|---|---|
| what is electromagnetic radiation | Energy that travels through space as waves with electric and magnetic fields. |
| What is wavelength (λ)? | distance between two peaks of a wave |
| What is frequency (ν)? | number of waves that pass a point each second |
| what is speed of light | 3.00 × 10⁸ m/s. |
| how is wavelength and frequency related | As one increases, the other decreases. |
| what is placks constant(h)? | 6.626 × 10⁻³⁴ J·s. |
| what does it mean that eneryg is quantized | energy comes in fixed packets, not continuous amounts. |
| what is a quantum | A single packet of energy. |
| what is photon | A particle (packet) of light. |
| equation for energy of photon | E = hν = hc/λ |
| what is photoelectric effect | When light knocks electrons off a metal surface. |
| why is threshold frequency important | It’s the minimum energy needed to remove an electron. |
| what is shortest waveltgh to longest | 1: Gamma rays 2: X-rays 3: Infrared radiation 4: Microwaves 5: Radio waves |
| In visible light, frequency decreases from violet to red: in what order | 1: Violet 2: Blue 3: Green 4: Orange 5: Red |
| how to measure mass | kg |
| length | meter |
| time | seconds |
| tempature | kelvin |
| amount | mole(mol) |
| electric current | ampere A |
| light intensity | candela cd |
| peta- P | 10^15 |
| tera- T | 10^12 |
| giga- G | 10^9 |
| mega- M | 10^6 |
| kilo- k | 10^3 |
| ×103 deci- d ×101 centi- c ×10-2 milli- m ×10-3 micro- μ ×10-6 nano- n ×10-9 pico- p ×10-12 femto- f ×10-15 | |
| what causes hydrogen emission spectrum | Excited hydrogen atoms emitting light as electrons fall to lower energy levels. |
| what is a line spectum | A spectrum consisting of discrete lines at specific wavelengths. |
| hat does hydrogen line spectrum prove | Electron energy levels are quantized. |
| what does quantized energy mean | Electrons can only have specific, discrete energy values. |
| who proposed bohr model | Niels Bohr. |
| main idea if bohr model | Electrons move in specific allowed orbits with fixed energies. |
| why did classical physic fail for atoms | It predicted electrons should spiral into the nucleus. |
| what is the bohr energy equation | E=−2.178×10−18(n2Z2 |
| what does a more negative energy mean | the electron is more tightly bound to the nucleus. |
| what happens when electron falls to lower level | A photon is emitted. |
| What does a negative ΔE indicate? | energy is released |
| What does a positive ΔE indicate? | energy absorbed |
| Why use |ΔE| in wavelength calculations? | wavelength cant be negative |
| What type of light excites hydrogen from n = 1 to n = 2? | ultraviolet light |
| what species does bohr model work for | One-electron species (H, He⁺, Li²⁺, etc.). |
Created by:
sahra_abdinoor