Why Atoms Bond: Valence Electrons and the Octet Rule

Question 1

During formation of NaCl, a sodium atom loses one valence electron and a chlorine atom gains it. What is the main result for the particles formed?

Accepted Answer

Na+ and Cl- have full outer shells like noble gases.

Answer

Both atoms change into argon atoms.

Answer

Each nucleus gains the electron instead of the outer shell.

Answer

Both particles become neutral atoms with half-filled shells.

Question 2

Why are valence electrons central to chemical bonding?

Accepted Answer

They are the outer electrons that are gained, lost, or shared to lower energy.

Answer

They are the protons that move between nuclei during reactions.

Answer

They are inner electrons that never affect an atom's charge.

Answer

They are neutrons that determine whether a bond is ionic.

Question 3

Magnesium reacts with oxygen to form MgO. Magnesium has two valence electrons, and oxygen has six. What electron change best explains the attraction in MgO?

Accepted Answer

Mg transfers two electrons to O, forming Mg2+ and O2-.

Answer

Mg and O each donate protons so both nuclei become oxygen.

Answer

O transfers six electrons to Mg so both atoms have empty outer shells.

Answer

Mg and O share every electron equally in one nonpolar molecule.

Question 4

Two chlorine atoms form Cl2. Which description matches the bond between them?

Accepted Answer

The atoms share a pair of valence electrons in a covalent bond.

Answer

One chlorine atom completely transfers an electron to the other.

Answer

Chlorine nuclei exchange protons to become different elements.

Answer

Positive metal ions are held together by delocalized electrons.

Question 5

A fluorine atom has seven valence electrons. Which change gives it an outer shell like neon?

Accepted Answer

gain one electron

Answer

lose seven electrons

Answer

gain seven protons

Answer

lose one neutron

Question 6

Nitrogen atoms form N2 with a triple bond. What does the triple bond mean about valence electrons?

Accepted Answer

The two atoms share three pairs of electrons.

Answer

One atom transfers three protons to the other.

Answer

Each atom loses all five valence electrons to the air.

Answer

The bond contains three neutrons between the nuclei.

Question 7

A neon atom rarely forms chemical bonds under normal classroom conditions. Which electron arrangement best explains this behavior?

Accepted Answer

Its valence shell is already filled with eight electrons.

Answer

Its nucleus has no protons to attract electrons.

Answer

It has one unpaired valence electron that is easy to share.

Answer

Its electrons are all lost before reactions begin.

Question 8

In H2O, oxygen forms two O-H bonds and has two lone pairs in a Lewis structure. What octet idea does this show for oxygen?

Accepted Answer

Two bonding pairs and two lone pairs place eight electrons around oxygen.

Answer

Oxygen becomes stable by having eight protons around its nucleus.

Answer

Oxygen needs no valence electrons once it bonds to hydrogen.

Answer

Two O-H bonds make oxygen's outer shell contain only two electrons.

Question 9

Potassium and bromine form KBr. Which statement distinguishes this bond from the bond in Br2?

Accepted Answer

KBr forms by electron transfer; Br2 forms by electron sharing.

Answer

KBr forms by sharing; Br2 forms by proton transfer.

Answer

Both bonds require bromine atoms to lose their nuclei.

Answer

Both bonds form because neutrons move between atoms.

Question 10

Carbon has four valence electrons. In methane, CH4, why does carbon form four single bonds?

Accepted Answer

Four shared pairs give carbon eight electrons in its valence shell.

Answer

Four hydrogen nuclei fill carbon's neutron shell.

Answer

Carbon loses four protons to become helium-like.

Answer

Each C-H bond removes a valence electron from carbon.

Question 11

What is the stability goal described by the octet rule for many main-group atoms?

Accepted Answer

to have eight electrons in the valence shell

Answer

to have eight protons in the nucleus

Answer

to have eight neutrons in every isotope

Answer

to have eight total atoms in each compound

Question 12

Hydrogen and chlorine form HCl. Chlorine is more electronegative than hydrogen. How are the bonding electrons used in this bond?

Accepted Answer

unequal sharing in a polar covalent bond

Answer

complete transfer that makes H+ and Cl-

Answer

proton sharing that changes chlorine into argon

Answer

delocalized electrons moving through a metal lattice

Question 13

An oxygen atom has six valence electrons. In many neutral covalent compounds, how many additional electrons must be counted around oxygen to satisfy the octet rule?

Accepted Answer

2

Answer

1

Answer

6

Answer

8

Question 14

When calcium forms Ca2+, it loses the two electrons in its fourth shell. Why is that ion more stable in many ionic compounds?

Accepted Answer

The next lower shell becomes the filled outer shell.

Answer

The calcium nucleus loses two protons at the same time.

Answer

The ion has no electrons left to repel each other.

Answer

The fourth shell stays half full and becomes less reactive.

Question 15

Two nonmetal atoms have similar electronegativities, and neither atom completely removes an electron from the other. Which bonding description fits?

Accepted Answer

They share valence electrons.

Answer

One atom forms a cation by giving away all protons.

Answer

Electrons are transferred completely from one atom to the other.

Answer

The atoms bond only by exchanging neutrons.

Question 16

Why does a Lewis structure focus on dots around an element symbol rather than on the nucleus?

Accepted Answer

The dots show valence electrons, which are the electrons involved in bonding.

Answer

The dots show neutrons, which decide the compound's formula.

Answer

The dots show protons moving from one atom to another.

Answer

The dots show atomic mass, which is the main cause of bonding.

Question 17

When magnesium forms MgCl2, what happens to magnesium's two valence electrons?

Accepted Answer

They are transferred to chlorine atoms.

Answer

They are converted into two protons.

Answer

They are shared equally by all atoms as lone pairs only.

Answer

They disappear, so mass is lost from the compound.

Question 18

Why do atoms generally release energy when a stable chemical bond forms?

Accepted Answer

Attractions between nuclei and valence electrons create a lower-energy arrangement.

Answer

Bonds form by destroying electrons, which removes their mass.

Answer

Bonding always forces every atom to gain protons.

Answer

Stable bonds require atoms to keep high potential energy.

Question 19

Why does the number eight keep appearing in Lewis structures for second-period atoms such as C, N, O, and F?

Accepted Answer

Their valence shell is full when it has two s electrons and six p electrons.

Answer

Their nuclei are stable only when they contain exactly eight protons.

Answer

Every stable atom must have eight total electrons, including inner electrons.

Answer

Eight atoms must join before any compound can exist.

Question 20

A sulfur atom has six valence electrons. In forming S2-, what electron arrangement is achieved?

Accepted Answer

an octet in the valence shell

Answer

two protons added to the nucleus

Answer

six electrons removed from the valence shell

Answer

a half-filled outer shell with four electrons

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Why Atoms Bond: Valence Electrons and the Octet Rule

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Why Atoms Bond: Valence Electrons and the Octet Rule

Ways to Play

Device Games: Students play on their phones

Blast Go

Zombie Escape

Avalanche

Maze Blast

Cave Climb

Blast Out

Mystery Auction

Tour Guide

Food Truck Rush

Tug of War

Alien Blast

Glacier Rush

Board Games: Teacher-led, projected to the class

Like what you see?

More like this

Bug Blast

BlastRace

BlastQuiz

BlastBoard

Seek & Destroy

Mystery Blast

Checkers

Texas Hold 'Em

Da Bomb

Castle Siege

Hot Potato

Market Mayhem

King of the Hill

Bank Heist

Top Corner