Question 1

Which of the following represents the correct condensed electron configuration for potassium (K, atomic number 19)?

Accepted Answer

$$[Ar] 4s^1$

Question 2

According to Hund's Rule, which orbital diagram correctly represents the ground state configuration for nitrogen (N, atomic number 7)?

Accepted Answer

Three electrons in the 2p orbitals, each occupying a separate orbital with parallel spins.

Question 3

Which element has the electron configuration $$1s^2$$ $$2s^2$$ $$2p^6$$ $$3s^2$$ $$3p^4$$?

Accepted Answer

Sulfur (S)

Question 4

What is the total number of valence electrons in a neutral atom of silicon (Si, atomic number 14)?

Accepted Answer

4

Question 5

Which of the following statements about core electrons is correct?

Accepted Answer

Core electrons are those in completely filled inner shells, including filled d or f sublevels.

Question 6

A transition metal has the condensed electron configuration $$[Ar] 4s^2$ 3d^6$. What is the element?

Accepted Answer

Iron (Fe)

Question 7

Which of the following elements is characterized by a $$ns^2$$ $$np^2$$ electron configuration in its outermost shell?

Accepted Answer

Carbon (C)

Question 8

How do the 1s and 2s electrons in boron differ from each other?

Accepted Answer

1s electrons are lower in energy, closer to the nucleus, and the 2s orbital has one node while 1s has none.

Question 9

Which of the following is the correct balanced chemical equation for the reaction of solid boron with fluorine gas to form boron trifluoride?

Accepted Answer

$$2B(s) + 3F_2(g) \rightarrow 2BF_3(g)$$

Question 10

Which of the following elements has a ground state electron configuration ending in $$4p^5$$?

Accepted Answer

Bromine (Br)

Question 11

What is the maximum number of electrons that can occupy the d orbitals in a given energy level?

Accepted Answer

10

Question 12

Which of the following is true about the electron configuration of chromium (Cr)?

Accepted Answer

It is $$[Ar] 4s^1$ 3d^5$ due to stability from half-filled d orbitals.

Question 13

Which block of the periodic table corresponds to elements filling the f orbitals?

Accepted Answer

Inner transition elements (lanthanides and actinides)

Question 14

How many unpaired electrons are present in the ground state electron configuration of oxygen (O, atomic number 8)?

Accepted Answer

2

Question 15

Which of the following elements has a condensed electron configuration of $$[Ne] 3s^2$ 3p^5$?

Accepted Answer

Chlorine (Cl)

Question 16

What is the order in which orbitals are filled according to the Aufbau principle?

Accepted Answer

$$1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d \rightarrow 4p$$

Question 17

Which of the following is a correct statement about isotopes of boron, $$^{10}B$$ and $$^{11}B$$?

Accepted Answer

They have the same electron configuration but different numbers of neutrons.

Question 18

Which of the following elements has a $$[Xe] 6s^2$ 4f$$^{14}$$ 5d$$^{10}$$ 6p^2$ electron configuration?

Accepted Answer

Lead (Pb)

Question 19

If an atom has a $$ns^2$$ $$np^6$$ electron configuration in its outermost shell, what is true about this atom?

Accepted Answer

It is a noble gas and chemically inert.

Electron Configurations and Atomic Structure: Study Notes

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