$1.204 \times 10^{24}$ molecules

Question 1

Which of the following statements best explains why elements form compounds?

Accepted Answer

Elements form compounds to achieve a more stable electron arrangement.

Question 2

What is the maximum number of electrons that can be found in the third energy level ($n = 3$) of an atom?

Accepted Answer

$18$

Question 3

Which group on the periodic table contains elements that are generally unreactive due to having a full valence shell?

Accepted Answer

Group 8A (noble gases)

Question 4

How many valence electrons does a phosphorus (P) atom have?

Accepted Answer

$5$

Question 5

A sodium atom ($Na$) loses one electron to form a sodium ion. What is the charge and electron configuration of the resulting ion?

Accepted Answer

Charge: $+1$, electron configuration same as neon

Question 6

Which of the following ions is isoelectronic with argon ($Ar$)?

Accepted Answer

$Cl^-$

Question 7

What is the correct formula for the ionic compound formed between magnesium and hydroxide?

Accepted Answer

$Mg(OH)_2$

Question 8

Which of the following compounds is named correctly?

Accepted Answer

$Na_2SO_4$: sodium sulfate

Question 9

Which of the following is a covalent compound?

Accepted Answer

$CO_2$

Question 10

How many moles are present in $24$ grams of carbon ($C$)? (Atomic mass of $C = 12$ g/mol)

Accepted Answer

$2$ moles

Question 11

What is the molar mass of $MgSO_4$? (Atomic masses: $Mg = 24.3$, $S = 32.1$, $O = 16.0$)

Accepted Answer

$120.3$ g/mol

Question 12

Which molecular shape does methane ($CH_4$) have according to VSEPR theory?

Accepted Answer

Tetrahedral

Question 13

What is the correct Lewis structure for water ($H_2O$)?

Accepted Answer

Oxygen atom with two single bonds to hydrogen and two lone pairs

Question 14

Which of the following molecules is nonpolar?

Accepted Answer

$CO_2$

Question 15

What is the electronegativity difference required for a bond to be considered ionic?

Accepted Answer

Greater than $1.8$

Question 16

Which of the following bonds is considered nonpolar?

Accepted Answer

$C-H$

Question 17

A molecule has a central atom with two bonding pairs and two lone pairs. What is its molecular shape?

Accepted Answer

Bent

Question 18

Which of the following is the correct name for $N_2O_5$?

Accepted Answer

Dinitrogen pentoxide

Question 19

How many molecules are present in $2$ moles of $CO_2$? (Avogadro's number $= 6.02 	imes 10^{23}$)

Accepted Answer

$1.204 	imes 10^{24}$ molecules

Question 20

Which of the following statements about polyatomic ions is correct?

Accepted Answer

Polyatomic ions consist of a group of nonmetals that form an ion with a charge for the entire group.

Electron Arrangements and the Octet Rule

Study Guide - Practice Questions