$$2n^2 = 2$$ \times $$3^2 = 18$

$$2 \times 1.01 + 16.00 = 18.02 g/$$mol

$$2.00 \times 6.022 \times 10$$^{23}$$ = 1.2044 \times 10$$^{24}$$ molecules

Question 1

Which of the following best describes the octet rule?

Accepted Answer

Atoms tend to gain, lose, or share electrons to achieve eight electrons in their valence shell.

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

$$2n^2 = 2$$ 	imes $$3^2 = 18$

Question 3

Which of the following ions is isoelectronic with neon ($$Ne$$)?

Accepted Answer

$$F^-$$

Question 4

A main-group element in Group 6A will typically form which ion?

Accepted Answer

$$2-$$ anion

Question 5

Which of the following is the correct formula for an ionic compound formed between magnesium and chlorine?

Accepted Answer

$$MgCl_2$$

Question 6

What is the name of the compound $$CuO$$?

Accepted Answer

Copper(II) oxide

Question 7

How many covalent bonds does a nitrogen atom typically form to complete its octet?

Accepted Answer

3

Question 8

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.

Question 9

What is the molar mass of water ($$H_2O$$)? (Atomic masses: H = 1.01 g/mol, O = 16.00 g/mol)

Accepted Answer

$$2 	imes 1.01 + 16.00 = 18.02 g/$$mol

Question 10

How many molecules are in 2.00 moles of $$CO_2$$? ($$N_A = 6.022 	imes 10$$^{23}$$ molecules/mol)

Accepted Answer

$$2.00 	imes 6.022 	imes 10$$^{23}$$ = 1.2044 	imes 10$$^{24}$$ molecules

Question 11

What is the molecular shape of ammonia ($$NH_3) $$according to VSEPR theory?

Accepted Answer

Trigonal pyramidal

Question 12

Which of the following bonds is the most polar?

Accepted Answer

$$H-F$$

Question 13

Which of the following molecules is nonpolar despite having polar bonds?

Accepted Answer

$$CO_2$$

Question 14

What is the correct name for $$N_2O_4$$?

Accepted Answer

Dinitrogen tetroxide

Question 15

Which of the following statements about polyatomic ions is correct?

Accepted Answer

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

Question 16

A sample contains $$3.01 	imes 10$$^{23}$$ molecules of O_2$. How many moles of O_2$ are present?

Accepted Answer

$$0.500$$ moles

Question 17

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

Accepted Answer

It has a bent shape and polar bonds, resulting in an uneven distribution of electrons.

Question 18

Which of the following is the correct formula for calcium phosphate?

Accepted Answer

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

Question 19

Which of the following statements about electronegativity is true?

Accepted Answer

Electronegativity increases as you move toward fluorine on the periodic table.

Question 20

How many valence electrons does an atom of sulfur ($$S) $$have?

Accepted Answer

6

Chapter 3: Compounds—How Elements Combine (GOB Chemistry Study Notes)

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