Question

question 29 (1 point)
the 3d subshell has a lower energy than the 4s subshell
true
false
question 30 (1 point)
pb, element 82, has 78 core electrons and 4 valence electrons
true
false
question 31 (1 point)
pb, element 82, can only form the +4 ion
true
false

Explanation:

• For Question 29: According to the Aufbau principle, the 4s subshell has a lower energy than the 3d subshell initially, so the statement is false.
• For Question 30: Lead (Pb) has an atomic number of 82. Its electron - configuration shows 78 core electrons and 4 valence electrons, so the statement is true.
• For Question 31: Lead (Pb) can form +2 and +4 ions due to the stability of its electron - configurations in these oxidation states, so the statement is false.

Answer:

Question 29: False
Question 30: True
Question 31: False