Question 1

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

Accepted Answer

Atoms form compounds to achieve a stable arrangement of eight electrons in their valence shell, known as the octet rule.

Question 2

How many electrons can be held in the third energy level ($$n = 3) of an $$atom?

Accepted Answer

$$18$$

Question 3

Which of the following elements has five valence electrons and will typically form three covalent bonds to complete its octet?

Accepted Answer

Nitrogen

Question 4

A sodium atom ($$Na) $$reacts with a chlorine atom ($$Cl) to $$form sodium chloride ($$NaCl). $$Which of the following best describes the process?

Accepted Answer

Sodium loses one electron to become a cation, and chlorine gains one electron to become an anion, forming an ionic bond.

Question 5

Which of the following is the correct name for the compound $$FeCl_3$$?

Accepted Answer

Iron(III) chloride

Question 6

What is the correct formula for calcium phosphate, given that the calcium ion is $$Ca^{2+}$$ and the phosphate ion is $$PO_4$$^{3-}$$?

Accepted Answer

$$Ca_3$$($$PO_4)_2$

Question 7

Which of the following molecules is nonpolar, despite containing polar bonds?

Accepted Answer

Carbon dioxide ($$CO_2)$$

Question 8

How many moles of $$H_2O$$ molecules are present in $$1.204 	imes 10$$^{24}$$ molecules of water?

Accepted Answer

$$2.00$$ moles

Question 9

Which of the following best describes the shape of a methane ($$CH_4) $$molecule according to VSEPR theory?

Accepted Answer

Tetrahedral

Question 10

What is the molar mass of glucose ($$C_6H_{12}O_6$)? (Atomic masses: C = 12.0$, H = 1.0$, O = 16.0$)

Accepted Answer

$$180.0 g/$$mol

Question 11

Which of the following statements about polyatomic ions is correct?

Accepted Answer

Most polyatomic ions end in –ate, while –ite is used for related ions with one fewer oxygen atom.

Question 12

Which of the following compounds contains a polar covalent bond?

Accepted Answer

HCl

Question 13

What is the correct name for the compound $$N_2O_5$$?

Accepted Answer

Dinitrogen pentoxide

Question 14

Which of the following best describes the difference between ionic and covalent bonds?

Accepted Answer

Ionic bonds involve the transfer of electrons from one atom to another, while covalent bonds involve the sharing of electrons.

Question 15

A molecule of ammonia ($$NH_3) $$has which molecular geometry?

Accepted Answer

Trigonal pyramidal

Question 16

Which of the following elements is the most electronegative?

Accepted Answer

Fluorine

Question 17

How many total electrons are present in a $$Ca^{2+}$$ ion?

Accepted Answer

$$18$$

Question 18

Which of the following best explains why water ($$H_2O) is a $$polar molecule?

Accepted Answer

Water has a bent shape and polar bonds, resulting in an uneven distribution of charge.

Question 19

Which of the following is the correct Lewis structure for methane ($$CH_4$$)?

Accepted Answer

A central carbon atom with four single bonds to four hydrogen atoms, no lone pairs on carbon.

Question 20

If a compound contains only nonmetals and its formula is $$PCl_5$$, what type of compound is it and how should it be named?

Accepted Answer

Covalent compound; phosphorus pentachloride

Compounds: How Elements Combine – Study Notes

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