$$1.204 \times 10$$^{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

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