How the model of the atom changed
Grade 10 Science Worksheet - Challenge Me
Circle the best answer, or write your answer on the line.
A hydrogen electron drops from n = 3 to n = 2 (rules on the sheet note). What wavelength does its photon have, to the nearest nm, Ari?
A hydrogen electron drops from n = 4 to n = 1 (rules on the sheet note). What wavelength does its photon have, to the nearest nm, Bo?
The 1926 quantum model fits helium, which Bohr's model could not. What did it keep from Bohr and what did it drop, Jun?
- Kept: nothing, since a new model must start over from entirely new evidence each time
- Kept: set energy levels. Dropped: fixed circular paths, now clouds of likely positions
- Kept: fixed circular paths. Dropped: set energy levels, since electrons can have any energy
Read this first
Hydrogen's energy levels in Bohr's model (from E = −13.6 ÷ n²)
level n energy (eV) 1 −13.60 2 −3.40 3 −1.51 4 −0.85 A hydrogen atom in level 1 meets photons of 10.2 eV and 11.0 eV (levels on the card). Which does Bohr's model absorb, Kira?
- Both, since each photon carries at least the 10.2 eV that the jump needs
- Neither, since lifting an electron up always needs the full 13.6 eV of ionization
- Only the 10.2 eV photon, which lifts the electron exactly from n = 1 to n = 2
A 14.0 eV photon hits hydrogen in level 1 (−13.60 eV on the card). What happens, Luz?
- The electron is freed and carries off the extra 0.4 eV as motion
- Nothing happens, since 14.0 eV does not match the gap to any level
- The electron jumps to level 2 and keeps 3.8 eV as extra energy
A student writes: Rutherford proved electrons orbit the nucleus like planets. Using the gold-foil results, what is the best verdict, Milo?
- Supported: a nucleus at the center means electrons must circle it like planets
- Supported: the large turns were caused by orbiting electrons pulling on the particles
- Not supported: foil results locate the positive charge but not how electrons move
Only 1 in 8,000 particles bounced back. In a short test of 800 particles, none did. Pia says that refutes the rate. What is the best reply?
- Yes: the rate predicts about 1 bounce in 800, and none appeared in the test
- No: at 1 in 8,000, 800 particles give about 0.1 bounces, so none is expected
- Yes: only a test of 8,000 or more particles can ever check a rate like this
A gold atom is about 3 × 10⁻¹⁰ m wide and its nucleus about 1.4 × 10⁻¹⁴ m (rounded). If the nucleus were a 1.4 cm marble, how wide would the atom be, Ren?
- About 30 m
- About 300 m
- About 3,000 m
Which model explains which observation (summary of the sheet)
observation Dalton Thomson Rutherford Bohr compounds form in whole-number ratios yes yes yes yes electrons come out of atoms no yes yes yes particles bounce back from foil no no yes yes hydrogen gives only a few colors no no no yes helium gives its own pattern of colors no no no no Tala reads the table. Which statement does it support?
- Each model explained every row its predecessor did; none explains helium's colors
- Bohr's model explains every row in the table, including the helium row
- Thomson's model explains why alpha particles bounce back from the gold foil
Card
Thomson's model (example numbers). Each atom bends an alpha particle by at most 0.01 degrees, in a random direction. Random bends add like the square root of their count. The foil is 1,000 atoms thick.
Using the card, which argument shows Thomson's model cannot give a 90 degree turn, Zee?
- Random bends cancel completely, so the total would be exactly zero, not 90 degrees
- Even with all 1,000 bends in line, the total is 10 degrees; random ones give 0.3
- 1,000 bends of 0.01 degrees easily add to 100 degrees, enough for a 90 degree turn