ChmPhyPP Ch. 6

7/29/2019 ChmPhyPP Ch. 6

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Objectives

Explain why atoms form bonds

Define chemical bond & name three types of

chemical bonds

Compare and contrast the advantages and

disadvantages of varying molecular models


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Bonding Atoms

Why do atoms bond?

- each atom wants a full outermost energy level

- gain, lose, and share valence electrons to achievethe duet or octet rule aka: being happy

- gives each atom an electron configuration similar

to that of a noble gas

ex. Group 18: He, Ne, Ar


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Chemical Bonds

Chemical Bonds

- attractive force that holds atoms or ions

together- 3 types

ionic, covalent, metallic

- determines the structure of compound- structure affects properties

- melting/boiling pts, conductivity etc.


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Chemical Structure/Models

Chemical Structure/Molecular Models

- arrangement of bonded atoms or ions

- bond length: the average distance between thenuclei of two bonded atoms

- bond angles: the angle formed by two

bonds to the same atom


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Molecular Models of Compounds

Ball and stick

- atoms are represented by balls

- bonds are represented by sticks

* good for seeing angles

Structural- chemical symbols represents atoms

- lines are used to represent bonds

* good for seeing angles H H

O


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Molecular Models Cont.

Space filling

- colored circles represent atoms, and the space theytake up

- no bonds, no bond angles

Electron Dot/Lewis Structure

- chemical symbol represent atom

- dots represent valence electrons

- 2 center dots represent a bond

- no bond angles, no bond length


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Objectives

Describe how an ionic, covalent and metallic bonds

forms

Relate the properties of ionic compounds to the

structure of crystal lattices

Compare polar and non polar bonds, and

demonstrate how polar bonds affect polarity of a

molecule

Describe the structure and strength of bonds in

metals & relate their properties to their structure


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Ionic Bonds / Ionic Compounds

Definition

- bond formed by the attraction between oppositelycharged ions

cation: positive: lost e-sanion: negative: gained e-s

- oppositely charged ions attract each other and form

an ionic bondex. Na+ + Cl- = NaCl

- electrons are transferred from one atom to another

- negative ions attract more positive ions, and soon a


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Ionic Bonds Cont.


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Networks / Crystal Lattices

Networks

- repeating pattern of multiple ions

ex. NaCl

- every Na ion is next to 6 Cl ions

- strong attraction between ions creates a rigidframework, or lattice structure: aka: crystals

ex, cubes, hexagons, tetragons


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Properties of Ionic Compounds

Structure affects properties- strong attractions between ions: strong bonds

- high melting/boiling pt

- shatter when struck (think of it as one unit)- conductivity

solid: ions are so close together, fixed

positions, (cant move)NO conductivity

liquid: ions are freely moving due to abroken lattice structure

Good conductivit


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Covalent Bonds Definition

- chemical bond in which two atoms share a pair ofvalence electrons

- can be a single, double, or triple bond

single, 2e-s (-); double, 4e-s (=); triple, 6e-s( )

- always formed between nonmetals

- mostly low melting/boiling points

2 types of bonds

- polar

- non polar


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Covalent Bond Cont.

Non Polar

- bonded atoms that share e-s equally

- same atoms bonded

ex. ClCl: Cl2

Polar

- bonded atoms that do not share e-

s equally- different atoms bonded

H

ex. HNH: NH3


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Covalent Bonds Cont.


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Metallic Bonds

Definition

- a bond formed by the attraction between positivelycharged metal ion (cation) and the shared electrons

that surround it (sea of electrons)ex. Cu

Properties

- Conductivity: Good: electrons can move freely

- Malleable: lattice structure is flexible


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Metallic Bonds Cont.


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Predicting Bond Type


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Objectives

Recognize monoatomic ions, metals with multiple

ions and polyatomic ions

Name and determine chemical formulas for

monoatomic ions, metals with multiple ion and

polyatomic ions


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Naming Ions Monoatomic Ions

- cation

-name of element with ion

ex. (Na) Sodium (Na+) Sodium ion

- anion

- name of element with the suffixide

ex. (Br) Bromine (Br-) Bromide

Ions with multiple cations

- transition metals

- most form 2+, 3+ and 4+

ex. Cu+ Cu2+


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Naming Metals with Multiple Ions

Transition Metals

- form multiple ions

- in order to name the ion use a roman numeral to

indicate the charge

ex. Cu2+: Copper (II), Titanium (III): Ti3+

Practice Problems:Fe3+: Iron (III) Mercury (III): Hg3+

Pb4+: Lead (IV) Chromium (II): Cr2+


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Polyatomic Ions

Definition

- an ion made of one or more atoms that arecovalently bonded and that act as a unit

(atoms that have lost or gained electrons)ex. CO3

2- , NH4

+

- behave the same as other ions

- polyatomic ions can combined likeany other ion (as a unit)

ex. NH4NO3 1:1 ratio

(NH4)2SO4 2:1 ratio


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Polyatomic Ions

Naming polyatomic ions

- not logical

- rules for some compounds

-ite & -ate endings

- indicates the presence of oxygen

- called oxyanions

- if (-) does not specify how many oxygen atomsare present

ex. Sulfate:4, Nitrate:3, Acetate:2


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Polyatomic Ions Cont.

- often several oxyanions differ only inthe number of oxygen atoms present

ex. Sulfur

- ion with more oxygen takes theateending

ex. SO4

- ion with less takes theite endingex. SO3

Common Oxyanions

* Make sure you know these: memorize


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Polyatomic Ions Cont.

Common Polyatomic Ions


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Objectives

Name ionic compounds from formulas

Determine the chemical formulas for ionic

compounds from compound name


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Naming Ionic Compounds

Naming ionic compounds (binary)Formula to Name

- name of cation followed by the name of the

anionex. NaCl: Sodium Chloride

ZnO: Zinc (II) Oxide

CuCl2: Copper (II) Chloride

- formulas must indicate the relative number of

cations and ions if transitional


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Naming Ionic Compounds

Practice Problems

MgBr2

Magnesium Bromide

KI

Potassium Iodide

CuCl2Copper (II) Chloride

Fe2S3

Iron (III) Sulfide


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Formulas of Ionic Compounds

Writing formulas for ionic compoundsName to Formula

- balance the cation charge and anion charge,

leaving NO net charge- use subscripts to denote the number of atoms in theformula

ex. NaCl: Na+

Cl-

: NaClCaCl: Ca2+ Cl- : CaCl2

**1 to 1 ratios do not designate charge**

**Criss-Cross char es into subscri ts**


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Practice Problems

Write the formula for the following atoms

a. lithium oxide

Li2

O

b. beryllium chloride

BeCl2

c. titanium (III) nitrideTiN

d. cobalt (III) hydroxide

Co(OH)3


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Objectives

Name Covalent compounds from formulas

Determine the chemical formulas for covalent

compounds from compound name


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Naming Covalent Compounds Prefix System

# of atoms prefix1 mono

2 di

3 tri4 tetra

5 penta

6 hexa

7 hepta

8 octa

9 nona

10 deca


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Naming Covalent Compounds Cont.

Rules for the prefix system

1. less electronegative element is given first. It isgiven a prefix only if it contributes more than one

atom to a molecule of the compound2. The second element is named by combining (a) aprefix indicating the number of atoms contributed bythe atom (b) the root of the name of the second

element, and (c) the endingide3. The o or a at the end of a prefix is usuallydropped when the word following the prefix beginswith another vowel

ex. Monoxide or pentoxide


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Naming Covalent Compounds Cont.

Naming covalent compounds from formula

1. SiO2

Silicon dioxide

2. PBr3

Phosphorus tribromide

3. CI4Carbon tetraiodide

4. N2O3

Dinitrogen trioxide

W iti F l f C l t


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Writing Formulas for Covalent

Compunds

Writing formulas from names

1. Carbon Dioxide

CO2

2. Dinitrogen Pentoxide

N2O5

3. Triphosphorus monosulfideP3S

4. Sulfur Monobromide

SB

ChmPhyPP Ch. 6

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