Which compound has the greatest lattice energy? 1. CaF2 vs. CaO 2. RbBr vs. CsBr

1. CaO (greater charges) 2. RbBr (shorter distance)

Chapter 4 Flashcards by Lexie Schoenrock

compounds are composed of atoms held together by _____ _____

chemical bonds

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Chemical bonds result from the attractions between _____ _____ (the electrons and protons) that compose atoms

charged particles

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Chemical bonds are classified into 3 types:

ionic, covalent, metallic

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ionic bonds occur between:

electrons are ____ between atoms (_____-_____)

metal and nonmetal

transferred (cation (metal) -anion (nonmetal))

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covalent bonds occur between:

electrons are ____ between atoms

nonmetal and nonmetal

shared

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metallic bonds occur between:

electrons are _____ between atoms (communal sharing)

metal and metal

“pooled”

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In a Lewis model: _____ _____ are represented as dots

valence electrons

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Lewis electron-dot structures depict the ______ formula with its valence electrons

structural

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Lewis structures focus on valence electrons because chemical bonding involves the transfer or sharing of ____ _____ between two or more atoms

valence electrons

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When atoms bond, they tend to gain, lose, or share electrons to result in a ____ ___-___ ______

noble gas-like configuration

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attractive interactions between cations and anions are called ____ ____

ionic bond

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Predict charge on the anion or cation formed for the following atoms:
Li:
F:
Ca:

Li: +1, cation
F: -1, anion
Ca: +2, cation

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Predict ionic compound formed between the following
Lithium and fluorine:
Calcium and chlorine:
Aluminum and oxygen:

LiF
CaCl2
Al2O3

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When anions and cations form, they form a structure and release energy from that formation. This structure is called a _____ _____

crystal lattice

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Ionic Compound Structures
The crystal lattice is held together by the electrostatic attraction of the ____ for all the surrounding ____
There is no ionic ______ - the chemical formula is an empirical formula, simply giving the ratio of ions based on ____ balance
The crystal lattice maximizes the _____ between cations and anions, leading to the most stable arrangement

cations, anions
molecule
charge
attraction

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the energy released when one mole of an ionic compound forms from its free ions in the gas phase

lattice energy

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lattice energy =

cation charge x anion charge / distance

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a stronger lattice energy =

greater charges

2. shorter distance

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Which compound has the greatest lattice energy?

CaF2 vs. CaO
RbBr vs. CsBr

CaO (greater charges)

2. RbBr (shorter distance)

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Rules for naming ionic compounds

the metal is named first and it keeps its elemental name
if the metal can have more than one charge, report its charge as a Roman numeral
the nonmetal is named second
Add -ide to the root of the nonmetal

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What is the chemical formula for aluminum sulfide?

Al₂S₃

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Covalently bound atoms compose a _____. Hence, they are referred to as _____ _____

molecule

molecular compounds

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Rules for naming molecular compounds

use prefix for both elements present (mono is emitted for the first name)
The first element keeps its elemental name
Add -ide to the root of the second element
Name the elements in the same order that they are written in the chemical formula

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Name prefixes for 
1
2
3
4
5
6
7
8
9
10

mono
di
tri
tetra
penta
hexa
hepta
octa
nona
deca

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Name each compound NI3 PCl5 N2O5

nitrogen triiodide phosphorous pentachloride dinitrogen pentaoxide

What is the formula for the molecule tetraphosphorus decasulfide?

P4S10

A group of atoms covalently bonded to create an ion

polyatomic ions

polyatomic ion with one or more oxygen atoms (not hydroxide and acetate)

oxoanions

give formula for potassium phosphate and magnesium cyanide

K3PO4 | Mg(CN)2

Give name for NaOH and Ca(CH3COO)2

sodium hydroxide and calcium acetate

a binary acid is a _____ combined with a _____ element | formula is followed by __

hydrogen; nonmetal element | aq

steps to naming a binary acid

1. add prefix hydro- to name of second element | 2. Replace last syllable in second element with -ic followed by acid

give the name for HBr (aq)

hydrobromic acid

Oxianions are bonded to an ____ Rules for naming oxianions if it ends in ___, it becomes ___ acid if it ends in ___, it becomes ___ acid

H+ if it ends in -ate, it becomes -ic acid if it ends in -ite, it becomes -ous acid

Gives the name of 1. H2SO4 (aq) 2. HCl (aq)

1. sulfuric acid | 2. hypochlorous acid

Lewis theory implies that some combinations should be _____, whereas others should not (these combinations result in _____) allows us to predict the _____ of molecules of covalently bonded substances predicts that covalently bonded compounds will be found as individual ______

stable; octets formulas molecules

What are the steps for drawing Lewis structures?

1. determine the total number of valence electrons 2. arrange symbol of elements to show how atoms are bonded together and connect them with a single bond 3. complete the octet of atoms bonded to central atom by adding lone pairs of electrons (hydrogen exception) 4. compare the number of valence electrons in Lewis structure to number determined in step 1 5. complete the octet on the central atom

What are bonding pairs?

covalent pairs are pairs of 2 shared valence electrons

single bond involves __ electrons double bond involves __ electrons triple bond involves __ electrons

2 4 6

What are lone pairs?

electron pairs that are not involved in bonds

What is the bond order?

number of bonds between two atoms

Extensions of Lewis theory suggest that there is some degree of delocalization of the electrons; the concept is called ______ delocalization of charge helps to _____ the molecule

resonance | stabilize

When there is more than one Lewis structure for a molecule that differ only in the position of the electrons, they are called _____ _____ The actual molecule is a combination of the resonance forms - a _____ ______ the molecule doesn't resonate between the two forms, though we often draw it that way

resonance structures

the blending of Lewis structure into a single composite, hybrid structure

resonance structure

resonance structures must have the same ____ only ____ positions can change they must have the same number of _____

connectivity electron electron

Lewis theory predicts that the more electrons two atoms share, the _____ the bond should be

shorter

_____ _____ is determined by measuring the distance between the nuclei of bonded atoms

bond length

In general, triple bonds are ____ than double bonds, and double bonds are ____ than single bonds

shorter, shorter

______ is required to break one mole of bonds | dependent on overall structure of the molecule

Energy

Bond energies ______ as bond length _____ (shorter bonds are _____)

increase; decreases; stronger

covalent bonding between unlike atoms results in _____ sharing of electrons. one atom pulls the electrons in the bond closer to its side, one end of the bond has larger electron density than the other The result is a ______ _____ bond

unequal | polar covalent

In a polar covalent bond, the end with the larger electron density gets a partial ______ charge, and the end that is electron-deficient gets a partial _____ charge

negative | positive

The ability of an atom to attract bonding electrons to itself is called _______

electronegativity

The larger the difference in electronegativity, the more ____ the bond _____ end toward more electronegative atom

polar | negative

Bond type of a molecule with a small electronegative difference (0-0.4)

covalent

Bond type of a molecule with an intermediate electronegative difference (0.5-2.0)

polar covalent

Bond type of a molecule with a large electronegativity difference (2.0+)

ionic (not a molecule)

How do you find formal charge?

hard: (# of valence electrons) - [(# of nonbonding electrons) + (1/2 x # of bonding electrons)] easy: valence electrons - dots - dashes

Concept of formal charge 1. The sum of all formal charges in a neutral molecule must be ____ 2. The sum of all formal charges in an ion must equal the ____ of the ion 3. ____ (or zero) formal charges on individual atoms are better than ____ ones 4. When formal charge cannot be avoided, negative formal charge should reside on the most _______ atom

1. zero 2. charge 3. small; large 4. electronegative

a molecule with an unpaired electron (this happens to molecules with an odd number of valence electrons)

radical species

radical species tend to be very ____ | Example:

reactive | nitric oxide

Octet rule states that electron sharing continues until __ electrons fill the outer shell

when the central atom is able to accommodate 10, 12, or even more electrons in the d orbitals

expanded valence shell

an expanded valence shell can arise in several ways: more _____ attach to a central atom more _____ bonds adding _____ _____ to the central atom

atoms double lone pairs

Only _-block atoms in period __ or later can expand valence shells Most common examples:

p-block; period 3 | S, P, Cl, Br, I, and Xe

Hydrogen forms a ____ (incomplete octet)

duet

______ and ______ form incomplete octets with three bonds and 6 total electrons

boron; aluminum

Chapter 4 Flashcards

(67 cards)