Question 1

Which of the following statements best explains why elements in the same group of the periodic table have similar chemical properties?

Accepted Answer

They have the same number of valence electrons.

Question 2

What is the electron configuration for chlorine (Cl), atomic number 17, using the noble gas shorthand notation?

Accepted Answer

$$[\mathrm{Ne}]\ 3s^2$\ 3p^5$

Question 3

How many valence electrons does silicon (Si) have, and in which principal energy level are they found?

Accepted Answer

Four valence electrons in the third principal energy level

Question 4

Which block of the periodic table contains the alkali metals?

Accepted Answer

s block

Question 5

What is the maximum number of electrons that can occupy the p block of a single period in the periodic table?

Accepted Answer

6

Question 6

Which of the following elements has a completely filled s subshell in its ground-state electron configuration?

Accepted Answer

Neon (Ne)

Question 7

A main group element is in group 5A and period 3. What is its outer electron configuration?

Accepted Answer

$$3s^2$$\ $$3p^3$$

Question 8

Which of the following best describes the difference between valence electrons and core electrons?

Accepted Answer

Valence electrons are in the outermost principal energy level, while core electrons are in all lower energy levels.

Question 9

Which element has the following electron configuration: $$[\mathrm{Ar}]\ 4s^2$\ 3d$$^{10}$$\ 4p^2$?

Accepted Answer

Germanium (Ge)

Question 10

Why is helium (He) placed in group 8A (or 18) even though its electron configuration is $$1s^2$$?

Accepted Answer

Because it has a completely filled outer shell, similar to other noble gases

Question 11

Which of the following is the correct order for filling orbitals as you move across the periodic table?

Accepted Answer

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

Question 12

Which of the following elements is a transition metal and why?

Accepted Answer

Iron (Fe), because its d subshell is being filled

Question 13

How many electrons are in the f block of the periodic table for a single period?

Accepted Answer

14

Question 14

Which of the following is the correct electron configuration for a neutral sodium (Na) atom?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^1$$

Question 15

Which of the following statements about the periodic table is FALSE?

Accepted Answer

The d block contains fourteen columns because the d subshell can hold fourteen electrons.

Question 16

Which element has the following outer electron configuration: $$4s^2$$\ $$4p^5$$?

Accepted Answer

Bromine (Br)

Question 17

A student claims that magnesium (Mg) has six valence electrons because it is in period 3. What is wrong with this reasoning?

Accepted Answer

The number of valence electrons is determined by the group number, not the period number.

Question 18

Which of the following elements has only one valence electron?

Accepted Answer

Potassium (K)

Question 19

Which of the following is a correct statement about the filling order of the 4s and 3d orbitals?

Accepted Answer

The 4s orbital fills before the 3d orbital.

Question 20

Which of the following is the correct electron configuration for a transition metal in the first row of the d block (e.g., Scandium, Sc)?

Accepted Answer

$$[\mathrm{Ar}]\ 4s^2$\ 3d^1$

Electron Configurations, Valence Electrons, and the Periodic Table

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