Question 1

Which of the following is the correct electron configuration for a neutral atom of phosphorus (atomic number 15)?

Accepted Answer

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

Question 2

Which element has the abbreviated electron configuration $$[Ar]\ 4s^2$\ 3d^7$?

Accepted Answer

Cobalt (Co)

Question 3

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

Accepted Answer

4

Question 4

Which of the following statements correctly describes the trend in atomic size for representative elements?

Accepted Answer

Atomic size increases down a group and decreases across a period from left to right.

Question 5

Which element would have the highest ionization energy among the following: Na, Mg, Al, or Cl?

Accepted Answer

Cl

Question 6

A patient is exposed to a new element with the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^4. $$Which group does this element belong to?

Accepted Answer

Group 6A (16)

Question 7

Which of the following elements has the greatest metallic character?

Accepted Answer

Potassium (K)

Question 8

Which of the following is the correct Lewis symbol for nitrogen (N)?

Accepted Answer

$$\cdot\!N\!\cdot ($$with three single dots around the symbol)

Question 9

Which of the following electron configurations represents an atom with a completely filled p sublevel in its outermost energy level?

Accepted Answer

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

Question 10

Which of the following best explains why ionization energy decreases as you move down a group in the periodic table?

Accepted Answer

Valence electrons are farther from the nucleus and are less strongly attracted.

Question 11

Which of the following is the correct electron configuration for a neutral atom of selenium (Se)?

Accepted Answer

$$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^2$$\ $$3d^{10}$$\ $$4p^4$$

Question 12

Which of the following elements is most likely to form a $$+1$$ ion based on its electron configuration and position in the periodic table?

Accepted Answer

Sodium (Na)

Question 13

Which of the following is an exception to the expected order of sublevel filling due to increased stability of a half-filled or filled d subshell?

Accepted Answer

Chromium (Cr)

Question 14

A certain element has the electron configuration $$[Ne]\ 3s^2$\ 3p^5$. Which element is this?

Accepted Answer

Chlorine (Cl)

Question 15

Which of the following statements about metallic character is correct?

Accepted Answer

Metallic character increases down a group and decreases across a period from left to right.

Question 16

Which of the following elements has the greatest number of unpaired electrons in its ground state electron configuration?

Accepted Answer

Nitrogen (N)

Question 17

Which of the following best describes the relationship between group number and valence electrons for representative elements?

Accepted Answer

The group number equals the number of valence electrons.

Question 18

Which of the following is the correct order of sublevel filling for the first 20 elements?

Accepted Answer

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

Question 19

A medical researcher is studying an unknown element with the electron configuration $$1s^2$$\ $$2s^2$$\ $$2p^6$$\ $$3s^2$$\ $$3p^6$$\ $$4s^1. $$Which element is this, and what is its most likely chemical property?

Accepted Answer

Potassium (K); it is highly reactive and forms $$+1$$ ions.

Electron Configurations and Periodic Trends: Study Notes for GOB Chemistry

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