Question

question 18 (1 point)
as changes in energy levels of electrons increase, the frequencies of atomic line spectra they emit
o a increase.
o b remain the same.
o c cannot be determined.
o d decrease.

question 19 (1 point)
what is another name for the representative elements?
o a transition elements
o b group a elements
o c group c elements
o d group b elements

question 20 (1 point)
which of the following elements is in the same period as phosphorus?
o a magnesium
o b oxygen
o c nitrogen
o d carbon

Explanation:

• Question 18: According to the formula \(E = h

u\) (where \(E\) is energy, \(h\) is Planck's constant, and \(
u\) is frequency), when the energy change (\(\Delta E\)) of electrons increases, since \(h\) is a constant, the frequency \(
u\) of the emitted atomic line spectra increases.

• Question 19: Representative elements are also known as Group A elements. Transition elements are a different category (in the d - block in some periodic table notations), and Group B and Group C are not the standard alternative names for representative elements.
• Question 20: Phosphorus (\(P\)) is in period 3 of the periodic table. Magnesium (\(Mg\)) is also in period 3. Oxygen (\(O\)), nitrogen (\(N\)), and carbon (\(C\)) are in period 2.

Answer:

• Question 18: a. increase
• Question 19: b. Group A elements
• Question 20: a. magnesium