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Compounds & Bonds – Unit 5
Why do atoms bond to form compounds?
How are bonds formed?
How do we represent compounds (names and formulas)?
Bonding Essentials
Bonds are formed when valence electrons are gained, lost or shared by atoms
There are 3 major types of bonds Ionic, Covalent, Metallic
Compounds are 2 or more atoms bonded together, with different properties than their elements.
Chemical Bonding
I. Compounds: Definition:
Properties of compounds:
Compounds can be decomposed (separated) only by chemical means (not physical).
Chemical Bonds
Force between 2 atoms Three bond types:
________________________
________________________
________________________
Electronegativity
Ability of an atom in a compound to attract electrons from another atom.
Difference between electronegativity of atoms is used to determine the bond type.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1H
2.1
2He
3Li
1.0
4Be1.5
5B
2.0
6C
2.5
7N
3.0
8O
3.5
9F
4.0
10Ne
11Na0.9
12Mg1.2
13Al1.5
14Si1.8
15P
2.1
16S
2.5
17Cl3.0
18Ar
19K
0.8
20Ca1.0
21Sc1.3
22Ti
1.5
23V
1.6
24Cr1.6
25Mn1.5
26Fe1.8
27Co1.9
28Ni1.9
29Cu1.9
30Zn1.6
31Ga1.6
32Ge1.8
33As2.0
34Se2.4
35Br2.8
36Kr3.0
37Rb0.8
38Sr1.0
39Y
1.2
40Zr1.4
41Nb1.6
42Mo1.8
43Tc1.9
44Ru2.2
45Rh2.2
46Pd2.2
47Ag1.9
48Cd1.7
49In
1.7
50Sn1.8
51Sb1.9
52Te2.1
53I
2.5
54Xe2.6
55Cs0.7
56Ba0.9
57La1.1
72Hf1.3
73Ta1.5
74W1.7
75Re1.9
76Os2.2
77Ir
2.2
78Pt2.2
79Au2.4
80Hg1.9
81Tl
1.8
82Pb1.9
83Bi1.9
84Po2.0
85At2.2
86Rn2.4
87Fr0.7
88Ra0.9
89Ac1.1
104Rf
105
Ha
106
Sg
107
Ns
108
Hs
109Mt
110
Uun
111Uuu
112Uub
Electronegativity Values for ElementsCircle elements with highest & lowest value & label.Show trends for EN using arrows.
Electronegativity Differences
Electronegativity Differences = ∆EN
O 3.2
Determining bond type
Determine the absolute
difference (either + or -)
Type?
O ___ - N____= _____
O ___ - O____=_____
O ___ - H____=_____
F____- Li ____=_____
Element EN
F 4.0 (4.1)
0 3.5
N 3.1
H 2.1
Li 1.0
Be 1.5
Electronegativity Learning Guide
Determine absolute differences Classify each bonding pair of elements as:
Ionic
Covalent If covalent, determine if the bond is:
non-polar (∆ 0 – 0.3) or
polar (∆0.4 – 1.7)
Ionic Bond∆EN = 1.8 – 3.2
Types of Bonds
Ionic
Covalent
Metallic
Ionic Bond
Ionic Bond: formed with
Bonds a __________ with a ____________
Valence electrons are ________________
from the ___________ to the __________.
Therefore, when the valence electron(s) are transferred to the ____-______, the NM become _______ charged (a ________).
Ionic bonds
The electronegativity difference must be equal to or greater than __________.
Ionic bonds look like:
Na Cl
Opposite charges attract= electrostatic attraction
Formula unit
Like the attraction of magnets
Ionic compounds
Ionic bonds form ionic compounds. An ionic compound is composed of positive (cations) and negative (anions) ions that are combined so that the negative and positive charges are equal.
Why do some atoms in formulas have subscripts and others do not?
Ionic Formula
Ionic formula units: The charges of the atoms in the compound must equal to zero.
Na ion (Na ) and Cl ion (Cl ) _______ + ________ = 0
Na ion (Na ) and Ca ion (Ca ) _______ + ________ = 0
Ionic compound names
Metal name + Non-metal (ide)
Prefix??
Note: will practice names & formulas after determining bonds
Opposites Attract
Find ions that can bond Write the symbol and the charge Write the new compound formed by
combining the ions. Name the compound. Write at least 15 compounds.
At least 10 should include subscripts.
Video: Discovery Ed
Ionic bonds
Covalent Bond
Non-metal and Non-metal
Sharing of electrons to form a bond
Covalent Bonds
Bonds a ___________ to a ___________.
Valence electrons are __________ between a _________ and a _________.
Electronegativity Difference
The electronegativity difference must be equal to or less than _______.
It is a polar covalent bond if the difference is between __________.
It is a non-polar covalent bond if the difference is between ___________.
Non-Polar Covalent Bond ∆EN= 0 – 0.3
The Electron pair that makes up the bond is shared evenly.
Non-Polar Covalent Bond
Polar Covalent Bond
Polar Covalent Bond∆EN = 0.4 – 1.7
The electron pair that makes up the bond is closer to the element that has the higher electronegativity.
Polar Covalent Bond
Covalent Bonds Covalent bonds form covalent compounds,
also called molecular compounds or molecules.Water Hydrogen
Polarity: unequal distribution of chargesOne side: more negative, The other side: more positive
Video: Discovery Ed – covalent bonds
Elements of chemistry: Compounds & Reactions
Metallic Bond
Metal to Metal
Electrons flow freely
Metallic Bonds
Bonds a _________ to a ____________. The valence electrons ________ ______
and are not bonded to one atom.
The valence electrons from a ______ of
________.
Metallic bond: Sea of electrons
The freedom of movement of the electrons in network of metals gives characteristic metallic properties:
-
-
-
Bond type
Compound(names & formulas)
Properties(physical and chemical)
Review
Metals __________ electrons because they have ________ electronegativity (EN)
Non-metals ________ electrons and have
________ electronegativity.
Warm-up: What type of bonds are created with:
Ionic, Covalent (non-polar or polar)
Use the PT (but not the electronegativity chart) Cr and Fe Rb and Br Cl and Cl H and F Ba and I S and S
Covalent Bonds – Strength
What is the Relationship between:- Bond energy & Bond length- Bond energy & Number of bonds
Intermolecular forces
What holds the separate covalent bonds together?
http://www.northland.cc.mn.us/favicon.ico
Lewis structures:A different way
Practice Lewis structures (electron dot) Structural formula (shows bonds with lines) Introduce shape of compounds
VSEPR Determine polarity Identify diatomic molecules (7)
Electronic cereal:
Start with diatomic molecules 2 atoms of the same element (7)
Rules to follow: Make every compound
1. Use different colors for each atom
2. Show how each atom contributes electrons to the bond and the lone pairs
3. Determine shape & polarity 1. Polarity is?
Electronic Cereal: F₂
Working with Moles
Peer Tutoring: Working in pairs
Mole Flow Chart
Mole
Mole Conversions (Factor Label Method)
Moles ↔ GramsMolar mass: 1 mole of = ? Grams
Moles ↔ Particles (atoms, molecules, compounds, etc.)
1 mole = atoms
Review scientific notation
Moles ↔ Volume of Gas (at STP)1 mole of a gas = Liters
What I know: Show work
What I need to know:
Formula for conversion Answer with correct units:
Analyze the problem:
What I know: Show work
What I need to know:
Formula for conversion Answer with correct units:
1. How many moles are in 100 Liters of Rn?
What I know: Show work
What I need to know:
Formula for conversion Answer with correct units:
#4 How many atoms are in 3.5 moles of Xe?
What I know: Show work
What I need to know:
Formula for conversion Answer with correct units:
#6 How many grams are in 3.75 moles of Kr?
Bond types determines properties of the compounds
Graphic organizer
Properties of Ionic Compounds
Structure: Crystalline solids (always)
Hardness Hard (like rocks)
Melting point: High
Boiling Point: High
Electrical Conductivity:
No : if solidYes: if melted or dissolved
Solubility in water:
Generally soluble
Properties of Covalent Compounds (molecules)
Structure Gas, Liquid or “soft” solid
Hardness Low Melting point Low to mediumBoiling Point Low to mediumElectrical conductivity NoSoluble in water Only if polar covalent
compound
Properties of Metallic Solids
Structure Solid
Hardness Medium (malleable, ductile)
Melting point Medium to high
Boiling point Medium to high
Electrical conductivity Yes
Soluble in water No
Ionic Bond
Ionic Compounds- Formulas
Opposites Attract
Find ions that can bond Write the symbol and the charge Write the new compound formed by
combining the ions. Name the compound. Write at least 15 compounds.
Ten should include subscripts.
Ionic CompoundsNames and Formulas
Binary
With Transition metals
With Polyatomic ions (Tertiary)
Transition metals can have more than one charge
Covalent CompoundsNames and Formulas
Review: Binary
Names & Formulas
Diatomic molecules
Acids
Bond type
Compound(names & formulas)
Properties(physical and chemical)
Foldable – Front cover Covalent Bonds
form Molecules
(Covalent compounds)
Ionic Bonds
form Ionic Compounds
Metallic Bonds
form Metallic Solids
Page 1
Covalent bond Picture
Ionic bond Picture
Metallic bond Picture
Type of atoms Electrons are: EN difference
Type of atoms Electrons are: EN difference
Type of atoms Electrons are:
Page 2
Molecules (covalent compounds) Lewis structure of water
Ionic Compounds (salts) Picture
Metallic solid
Properties of molecules
Properties of Ionic compounds
Properties of metallic solids
Page 3
Common examples of molecules
Common examples of ionic compounds
Common examples of metallic solids
Names & formulas- Binary molecules
- Binary ionic compounds
- Brass- Pewter- Sterling silver- Stainless steel
Page 4 – names & formulas
Molecules Diatomic molecules Acids
Ionic Compounds Transition metals Polyatomic ions
Metallic solids Bronze Gold
Lewis Diagrams Count and add the valence electrons for each atom. Put C as the central atom (or element with with
lowest electronegativity). Hydrogen is never the central atom
Place 2 electrons for each bond between 2 atoms. Arrange the other electrons evenly around the atoms
to satisfy the octet rule. Duet rule for H. If there are not enough electrons, make double or triple
bonds.
Lewis Diagrams
Valence Shell
Electron Pair Repulsion
VSEPR
This means:
Ionic Bond
