Chapter 8

Question 1

In nature only what exists as single atoms?

These are ?

Answer 1

• In nature, only the noble gases exist as single atoms
• They are monatomic
• Helium (He)
• Neon (Ne)
• Argon (Ar)
• Etc

Question 2

Mono =

Answer 2

One

Question 3

But not all elements are _________, instead they exist as groups of atoms or ________

Answer 3

• not all elements are monoatomic, instead they exist as groups of atoms or molecules

Question 4

A ___________ is a _________ group of atoms joined together by ___________ _______

Answer 4

• A molecule is a neutral group of atoms joined together by covalent bonds

Question 5

What’s a covalent bong and what’s happening in a covalent bon?
Example of a covalent bond?

Answer 5

Covalent Bonds
• atoms are held together by sharing electrons
• There is a “tug of war” for electrons
• Examples: H20 and CO2

Question 6

What’s a diatomic molecule?
At room temperature, what are most diatomic molecules?
Diatomic molecules are either __________ or __________

Answer 6

Diatomic Molecule
• molecule that contains two atoms
• At room temperature most diatomic molecules are gases
• Diatomic molecules are either homonuclear or heteronuclear

Question 7

BrINClHOF

Answer 7

bromine, iodine, nitrogen, chlorine, hydrogen, oxygen, fluorine

Question 8

Define a molecular compound

Answer 8

a molecular compound is formed when two or more atoms join together chemically through covalent bonds
• H2O - these molecules always represent water

Question 9

Define a molecular formula?
What’s a molecular formula show?
What’s H20 represent?
What does molecular formula not tell you?

Answer 9

a molecular formulas is the chemical formula of a molecular compound
• A molecular formula shows how many atoms of each element a substance contains
• H2O represents 2 hydrogen atoms to 1 oxygen atom
• It does not tell you the structure or arrangement of the atoms in space

Question 10

What are molecular diagrams and models used for?

What’s molecular structure?

Answer 10

Molecular Diagrams and models
• used to show the arrangement of atoms in a molecule
• The arrangement of the atoms within a molecule is called its molecular structure
• The following are space filling molecular models

Question 11

Define Ionic compound?
What holds ions together in Ionic compounds?
Ionic compounds are electrically _____?
Example of an Ionic compound?

Answer 11

Ionic bonds
• Ionic compound is a compound composed of cations and anions
• Electrostatic forces hold ions together in Ionic compounds
• The Ionic compounds are electrically neutral
• NaCl and MgSO4

Question 12

A molecular compound is a ___________ unit?
Molecular compounds have higher or lower melting points?
Molecular compounds have lower or higher boiling points?
Molecular compounds are what at room temperature?
Molecular compounds are metals or nonmetals?
Are molecular compounds flammable?
Molecular compounds do or don’t conduct electricity?

Answer 12

Molecular compounds 
• representative unit: molecule
• Lower melting points 
• Lower boiling points 
• Gases or liquids at room temp 
• Nonmetals 
• Flammable 
• Don’t conduct electricity

Question 13

An Ionic compound is a __________ unit?
Ionic compounds are what at room temperature?
Are Ionic compounds metals or non metals?
Ionic compounds can conduct electricity in _________ _________

Answer 13

Ionic compounds 
• representative unit: formula unit 
•  Crystalline structures at room temp 
• Combinations of metals and nonmetals 
• Can conduct when dissolved in water

Question 14

Chemical formulas sometimes also Calle __________. formulas are the ________. Way of what?
Elmer symbols indicate what?
What are subscripts used for?

Answer 14

Molecular formula
• chemical formulas sometimes also called molecular formulas are the simplest way of representing molecules
• Elemental symbols from the periodic table indicate which elements are present
• Subscripts are used to indicate how many atoms of each molecule

Question 15

Is there a single NaCl unit?
What is NaCl made up of? What are these atoms joined as?
One piece of NaCl is referred to as a ______ unit, not a ________

Answer 15

Formula unit
• there is no such thing as a single NaCl unit
• NaCl is actually made up of multiple sodium and chloride ions joined together in a large crystal lattice
• One piece of NaCl is referred to as a formula unit, not a molecule
• The smallest whole number ratio of ions

Question 16

in a covalent bonds, electrons sharing occurs so that atoms attain?
Which groups on the periodic table are likely to form covalent bonds?

Answer 16

The octet rule in covalent bonding
• in a covalent bonds, electrons sharing occurs so that atoms attain the electron configuration of a noble gas
• combinations of atoms of the nonmetals and metalloids in groups 4A, 5A, 6A, and 7A of the periodic table are likely to form covalent bonds
• The combined atoms usually acquire a total of eight electrons or an octet

Question 17

Define single covalent bonds

Answer 17

Single covalent bonds

• two atoms held together by shading one pair of electrons are joined by a Single covalent bond

Question 18

Define structural formula

Answer 18

structural formula represents the covalent bonds as dashes and shows the arrangement of covalently bonded atoms

Question 19

Define molecular formula

Answer 19

• A molecular formula of hydrogen, H2, indicates only the number of hydrogen atoms in each molecule

Question 20

What does electron dot structure represent

Answer 20

Electron dot structure

• represents the shared pair of electrons of the covalent bond by two dots

Question 21

Electron dot structure for diatomic atoms

Answer 21

Electron dots structure of a diatomic atoms
• each fluorine atom contributes one electron to complete the octet
• The fluorine atoms share only one pair of valence electrons

Question 22

Double and triple covalent bonds

Answer 22

Double and triple covalent bonds
Atoms for, double and triple covalent bonds if they can attain a noble gas structure by sharing two or three pairs of electrons

Question 23

What element doesn’t follow the octet rule

Answer 23

Oxygen

Question 24

Define a polyatomic ion

Answer 24

Polyatomic ions
• a polyatomic ion, such as NH4+, is a tight bond group of atoms that has a positive or negative charge and behaves as a unit

Question 25

Define coordinate covalent bond

Answer 25

Covalent bond in which one atom contributes both bonding electrons.

It shares an entire pair of electrons

Question 26

Exceptions to the octet rule

Answer 26

the octet rule cannot be satisfied in molecules whose total number of valence electrons is an odd number
• - NO2
• - ClO2
• - NO
• Boron; the atom acquire less than an octet of 8 electrons
• Sulfur, phosphorus, expand the octet to 10 or 12

Question 27

Define bond dissociation energies

Answer 27

a large quantity of heat is released when hydrogen atoms combine to form hydrogen molecules
• The release of heat suggests that the product is more stable than the reactant
• The energy required to break the bond between two covalently bonded atoms is the bond dissociation energy
• Units are given in Kj/mol
• A large bond dissociation energy corresponds to a strong covalent bond
• Compounds with high dissociation energy tend to be quite unreactive
• C - C
• C - H
• H- H

Question 28

Define resonance

Answer 28

when there are two different electron dot structures they can convert from one structure to the next
• Resonance structures are structures that occur when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for s molecule of ion

Question 29

What is an atomic orbital

Answer 29

What is an atomic orbital
• a region of space where an electron is most likely to be found
• S1 orbitals is spherical

Question 30

What is a molecular orbital

Answer 30

What is a molecular orbital
• When two atoms get close enough, their orbitals merge to include both nuclei this is a molecular orbital
• Orbitals that apply to the entire molecule

Question 31

Similarities of atomic orbits vs. molecular orbits

Answer 31

• Each atomic orbital is filled with two electrons
• Each molecule orbit is filled with two electrons
• Just as an atomic orbital to a particular atom, a molecular orbital belongs to a molecule as a whole

Question 32

Define bonding orbitals

Answer 32

Bonding orbitals

• a molecular orbital that can be occupied by two electrons of a covalent bond

Question 33

What’s a sigma bond

Answer 33

when two atomic orbitals combine 
• To become a molecular orbital 
• And they form a symmetric orbital around the axis connecting the two atomic nuclei 
• A sigma bond is formed 
  * sigma = symmetrical

Question 34

Sigma =

Answer 34

Symmetrical

Question 35

What’s happening in a sigma bond

Answer 35

What’s happening in a sigma bond?
• the nuclei and the electrons attract each other
• The nuclei repel each other
• The electrons repel each other
• In hydrogen the binding of the nuclei and electrons is stronger than the repulsion of the electrons or of the nuclei to each other
• There for this results in a stable diatomic molecule of H2

Question 36

Sigma bonds with p orbitals

Answer 36

• fluorine atoms have a half filled 2p orbital when two fluorine molecules come together they produce s molecular orbit
• There is a high probability of finding two electrons between the positively charged nuclei
• Th nuclei are attracted to the electron pairs two atomic orbitals overall to form a sigma bonding molecule

Question 37

Define a pi bond

Answer 37

Pi bonds
• in some orbitals the orbitals can overlap side by side
• These are called pi orbitals
• Pi orbitals overlap less than sigma bonds and therefore tend to be weaker

Question 38

Define the VSEPR Theory

Answer 38

VSEPR Theory
• in order to explain the 3-dimensional shape of molecules, scientists use valence shell electron pair repulsion theory
• States that the repulsion between electron pairs causes molecular shapes to adjust so that the valence electron pairs stay as far apart as possible

Question 39

Linear model

Answer 39

Linear Model
• AB2
• H - Be - H
• CO2
• 180 degrees 
• Sp hybridization

Question 40

Un paired electrons are held closer to ?

Unpaired electrons strongly repel what?

Answer 40

Unpaired electrons
• unpaired electrons are held closer to the central atom
• Unpaired electrons strongly repel the bonding pairs, pushing them together

Question 41

To unshared electrons

Answer 41

water
• oxygen forms a single covalent bond with two hydrogen atoms and two unshared electrons
• They form a tetrahedral arrangement around the central oxygen
• A water molecule is bent

Question 42

Water molecule

Answer 42

• Water has two bonding pairs and two unshared pairs of electrons to form a tetrahedral arrangement around oxygen
• the two unshared pairs repel the bonding pairs creating a bent shape
• The hydrogen atoms are only 105 degrees apart

Question 43

Trigonal Planar

Answer 43

Trigonal Planar 
• boron trifluoride 
• BF3 
• Angles 120 degrees 
• Sp^2 hybridization

Question 44

Tetrahedral angle

Answer 44

Tetrahedral Angle
• methane (CH4) has 4 hydrogen that are at the four corners of a geometrical solid called a regular tetrahedron
• All of the C-H angles are 109.5 degrees (the tetrahedral angle)

Question 45

Un paired electrons

Electron dot structure fails to reflect what?

Answer 45

electron dot structure fails to reflect the 3-dimensional shapes of the molecules illustrated
• The unpaired electrons are held closer to the nitrogen atom than are the bonded hydrogen
• The unpaired strongly repels the bonding pairs pushing them together