chemical bonding they call it bonding…chemical bonding

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CHEMICAL BONDING THEY CALL IT BONDING…CHEMICAL BONDING

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CHEMICAL BONDING

THEY CALL IT BONDING…CHEMICAL BONDING

Bonding Atoms

Why do atoms bond?

- each atom wants a full outermost energy level

- gain, lose, and share valence electrons to achieve the 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

Chemical Structure/Models

Chemical Structure/Molecular Models

- arrangement of bonded atoms or ions

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

- bond angles: the angle formed by two bonds to the same atom

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

Molecular Models Cont.

Space filling

- colored circles represent atoms, and the space they take 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

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.

Predicting Bond Type

Ionic Bonds / Ionic Compounds

Definition

- bond formed by the attraction between oppositely charged ions

cation: positive: lost e-’s

anion: negative: gained e-’s

- oppositely charged ions attract each other and form an ionic bond

ex. Na+ + Cl- = NaCl

- electrons are transferred from one atom to another

- negative ions attract more positive ions, and soon a network is formed

Properties of Ionic CompoundsStructure 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, (can’t move)

NO conductivity

liquid: ions are freely moving due to a broken lattice structure

Good conductivity

Covalent BondsDefinition

- chemical bond in which two atoms share a pair of valence 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

Covalent Bond Cont.

Non Polar

- bonded atoms that share e-’s equally

- same atoms bonded

ex. Cl – Cl: Cl2

Polar

- bonded atoms that do not share e-’s equally

- different atoms bonded

H

ex. H – N – H: NH3

Metallic Bonds

Definition

- a bond formed by the attraction between positively charged 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

Naming Ions Monoatomic Ions

- cation

-name of element with ion

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

- anion

- name of element with the suffix –ide

ex. (Br) Bromine (Br-) Bromide

Ions with multiple cations

- transition metals

- most form 2+, 3+ and 4+

ex. Cu+, Cu2+

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+

Polyatomic Ions

Definition

- an ion made of one or more atoms that are covalently 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 like

any other ion (as a unit)

ex. NH4NO3 1:1 ratio

(NH4)2SO4 2:1 ratio

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 atoms are present

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

Polyatomic Ions Cont.- often several oxyanions differ only in

the number of oxygen atoms present

ex. Sulfur

- ion with more oxygen takes the –ate ending

ex. SO4

- ion with less takes the –ite ending

ex. SO3

Common Oxyanions

* Make sure you know these: memorize

Polyatomic Ions Cont.

Common Polyatomic Ions

Naming Ionic Compounds

Naming ionic compounds (binary)

Formula to Name

- name of cation followed by the name of the anion

ex. NaCl: Sodium Chloride

ZnO: Zinc (II) Oxide

CuCl2: Copper (II) Chloride

- formulas must indicate the relative number of cations and ions if transitional

Naming Ionic Compounds

Practice Problems

MgBr2

Magnesium Bromide

KI

Potassium Iodide

CuCl2

Copper (II) Chloride

Fe2S3

Iron (III) Sulfide

Formulas of Ionic Compounds

Writing formulas for ionic compounds

Name to Formula

- balance the cation charge and anion charge, leaving NO net charge

- use subscripts to denote the number of atoms in the formula

ex. NaCl: Na+ Cl- : NaCl

CaCl: Ca2+ Cl- : CaCl2

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

**Criss-Cross charges into subscripts**

Practice Problems

Write the formula for the following atoms

a. lithium oxide Li2O

b. beryllium chloride BeCl2

c. titanium (III) nitride

TiN

d. cobalt (III) hydroxide

Co(OH)3

Naming Covalent Compounds Prefix System

# of atoms prefix

1 mono

2 di

3 tri

4 tetra

5 penta

6 hexa

7 hepta

8 octa

9 nona

10 deca

Naming Covalent Compounds Cont.

Rules for the prefix system

1. less electronegative element is given first. It is given a prefix only if it contributes more than one atom to a molecule of the compound

2. The second element is named by combining (a) a prefix indicating the number of atoms contributed by the atom (b) the root of the name of the second element, and (c) the ending –ide

3. The o or a at the end of a prefix is usually dropped when the word following the prefix begins with another vowel

ex. Monoxide or pentoxide

Naming Covalent Compounds Cont.

Naming covalent compounds from formula

1. SiO2

Silicon dioxide

2. PBr3

Phosphorus tribromide

3. CI4

Carbon tetraiodide

4. N2O3

Dinitrogen trioxide

Writing Formulas for Covalent Compunds

Writing formulas from names

1. Carbon DioxideCO2

2. Dinitrogen Pentoxide

N2O5

3. Triphosphorus monosulfide

P3S

4. Sulfur Monobromide

SBr