Answer
Chemical formula or Chemical Abstracts Service
Explanation:
A CAS (Chemical Abstracts Service) Registry Number is a unique identifier that tells you, for example, that acetone and dimethyl ketone are actually the same substance.
Ca, V, Cu, Kr
Remember a period is a the horizontal rows in the Periodic Table.
The earth moves faster than the planets that have farther from the sun
Answer:
1.26 × 10¹⁵ s⁻¹
Explanation:
Work function is the minimum energy required to remove an electron from the surface of metal
energy of the electron = hf - Φ
Φ = work function = hf₀ where f₀ = threshold frequency
f₀ = Φ / h where h ( Planck constant = 6.626 × 10⁻³⁴ Js)
Φ = 5.22eV = 5.22 × 1 eV where 1 eV = 1.60217662 × 10⁻¹⁹ J
Φ = 5.22 × 1.60217662 × 10⁻19 J = 8.363362 × 10⁻¹⁹ J
f₀ = (8.363362 ×10⁻¹⁹ J) / (6.626× 10⁻³⁴ Js) = 1.26 × 10¹⁵ s⁻¹
The frequency must be greater than the 1.26 × 10¹⁵ s⁻¹ to observe the emission
