Chapter 3- Crysttal Binding

7/28/2019 Chapter 3- Crysttal Binding

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Chapter -3-Crystal

Binding

Atom the smallest unit of

matter indivisible

Helium

atom

electron shellsa) Atomic number = number of Electrons

b) Electrons vary in the amount of energy

they possess, and they occur at certain

energy levels orelectron shells.

c) Electron shells determine how an atom

behaves when it encounters other atoms

Electrons are placed in shells according torules:

1) The 1st shell can hold up to two electrons,

and each shell thereafter can hold up to 8

electrons.

Octet Rule = atoms tend to gain, lose or share electrons so

as to have 8 electrons

C would like to

N would like to

O would like to

Gain 4 electrons

Gain 3 electronsGain 2 electrons

Why are electrons important?

1) Elements have different electron

configurations

different electron configurations mean

different levels of bonding


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Electron Dot Structures

Symbols of atoms with dots to represent thevalence-shell electrons

1 2 13 14 15 16 17 18

H He:

Li Be B C N O : F :Ne :

Na Mg Al Si P S :Cl :Ar:

valence e-s

symbol represents

nucleus & core e-s

Each side = orbital (s orp)

dot = valence e- (8 max)

dont pair up until they

have to (Hunds rule) X(s)

(px)

(pz)

(py)

Electron Dot diagram for

Nitrogen

Nitrogen has 5 valence e-write symbol

Nput first 2 e- on rt side

Add remaining e-s CCW

The Octet Rule Noble gases unreactive

Octet Rule: noble gas configuration

8 outer level (stable)

noble gas has 8 e-s in outer level

(He has 2)

Metals lose e-s to attain a noble gas

configuration (NGC).

They make + ions (cations)

Na 1s22s22p63s1 1 valence e-

Na1+ 1s22s22p6 (NGC w/ 8 valence e-

s)


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Metals have few valence e-s (usually 3or less); calcium has only 2 valence e-s

Ca

Metals few valence e-s Metals lose

Ca

Form + ions

Ca

2+

NO DOTSshown for cation

This is named the

calcium ioncalcium ion..

Scandium (21)

e- configuration is:

1s22s22p63s23p64s23d1

lose 2e

-

(2+), or lose 3e

-

(3+)Sc = Sc2+

Scandium (II) ion Scandium (III) ion

Sc = Sc3+Sc

Silver (47)

Predictedconfiguration is:1s22s22p63s23p64s23d104p65s24d9

Actualconfiguration is:1s22s22p63s23p64s23d104p65s14d10

Ag = Ag1+ (cant lose any more,charges of 3+ or greater are uncommon)

Silver did the best job it could,

but it did not achieve true NGC

pseudo-noble gas

configuration


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Nonmetals gain e-s to attain NGC - ions (anions)

S = 1s22s22p63s23p4 = 6 valence e-

S2- = 1s22s22p63s23p6 = NGC

Halide ions - ions from halogens thatgain e-s

Nonmetals have many valence e-s

(usually 5+)

gain e-s

P3-

(called phosphide ion, and

should showdots)

All atoms react to achieve NGC

Noble gases s2p6

8 valence e-s (stable)

octet rule

ArElectron dot activity

Practice problems

1. Write the name and symbol of the ion

formed when

A. A sulfur atom gains two electrons

B. An aluminum atom loses three electrons

Practice problems

2. how many electrons are lost or gained

in forming each ion?

A. Ba2+ B. As3- C. Cu2+

OBJECTIVES:

Explain the

electrical charge of

an ionic compound.


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Learning Check

A. X would be the electron dot formula for

1) Na 2) K 3) Al

B. X would be the electron dot formula

1) B 2) N 3) P

Learning Check

A. Number of valence electrons in aluminum

1) 1 e-2) 2 e-3) 3 e-

B. Change in electrons for octet

1) lose 3e-2) gain 3 e-3) gain 5e-

C.Ionic charge of aluminum

1) 3-2) 5-3) 3+

Solution

A. Number of valence electrons in aluminum

3) 3 e-

B. Change in electrons for octet

1) lose 3e-

C. Ionic charge of aluminum

3) 3+

Learning Check

Give the ionic charge for each of the

following:

A. 12 p+ and 10 e-

1) 0 2) 2+ 3) 2-

B. 50p+ and 46 e-

1) 2+ 2) 4+ 3) 4-

C. 15 p+ and 18e-

2) 3+ 2) 3- 3) 5-

Chemical bonds: an attemptto fill electron shells

1. Ionic bonds

2. Covalent bonds

3. Metallic bonds

1- IONIC BONDbond formed between

two ions by the

transferof electrons


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Formation of Ions from Metals

Ionic compounds result when metals react withnonmetals

Metals lose electrons to match the number of

valence electrons of their nearest noble gas

Positive ions form when the number of

electrons are less than the number of protons

Group 1 metals ion 1+



Formation of Sodium Ion

Sodium atom Sodium ionNa e Na +

2-8-1 2-8 ( = Ne)

11 p+ 11 p+

11 e- 10 e-

0 1+

Formation of Magnesium Ion

Magnesium atom Magnesium ion

Mg 2e Mg2+

2-8-2 2-8 (=Ne)

12 p+ 12 p+

12 e- 10 e-

0 2+

Some Typical Ions with

Positive Charges (Cations)

Group 1 Group 2 Group 3

H+ Mg2+ Al3+

Li+ Ca2+

Na+

Sr2+

K+ Ba2+

Fluoride Ionunpaired electron octet

1 -

: F + e : F :

2-7 2-8 (= Ne)

9 p+ 9 p+

9 e- 10 e-

0 1 -

ionic charge

Ionic BondBetween atoms of metals and

nonmetals with very different

electronegativity

Bond formed by transfer of electrons

Produce charged ions all states.

Conductors and have high melting

point.

Examples; NaCl, CaCl2, K2O


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1). Ionic bond electron from Na is transferred to Cl,this causes a charge imbalance in each atom. The Na

becomes (Na+) and the Cl becomes (Cl-), charged

particles or ions.

Ionic Bonds

Ionic Bonds Ionic Bonding

RNave, Georgia State Univ at hyperphysics.phy-astr.gsu.edu/hbase/molecule


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,must be accounted fors-eAll

each atom has NGC (stable)

Ca P

combining calcium and phosphorus:

Ca P

Ca2+ P

Ionic Bonding

Ca2+ P

Ca

Ionic Bonding

Ca2+ P3-

Ca

Ionic Bonding

Ca2+ P3-

Ca P


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Ionic Bonding

Ca2+ P3-

Ca2+ P

Ionic Bonding

Ca2+ P3-

Ca2+ P

Ca

Ionic Bonding

Ca2+ P3-

Ca2+ P3-

Ca2+

Ionic Bonding

= Ca3P2 Formula Unitchemical formula - shows kinds andnumbers of atoms in smallest representative

particle of substance.

Formula Unit -smallest representative

particle in ionic cmpd

Ionic bonds 6:28

- Page 198

Coordination Numbers:

Both the sodium

and chlorine have 6

Maximizes contact

btwn opp charges

Both the cesium

and chlorine have 8

Each titanium has

6, and each oxygen

has 3

NaCl

CsCl

TiO2

OBJECTIVES:

Describe three

properties of ionic

compounds.


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2. Covalent bonds-Two atoms share one or more pairs of outer-shell

electrons.Oxygen AtomOxygen Atom Oxygen AtomOxygen Atom

Oxygen Molecule (OOxygen Molecule (O22))

COVALENT BONDbond formed by the sharingof

electrons Between nonmetallic elements of similar

electronegativity.

Formed by sharing electron pairs

Stable non-ionizing particles, they are not

conductors at any state

Examples; O2, CO2, C2H6, H2O, SiC

Covalent Bonding A covalent bond forms when two non-metal atoms share a

pair of electrons the electrons involved are in the highest

occupied energy levels (outer shells) of the atoms

An atom that shares one or more of its electrons will

complete its highest occupied energy level

Covalent bonds are strong a lot of energy is needed tobreak them

Substances with covalent bonds often form molecules with

low melting and boiling points, such as hydrogen and water

Bonds in all the polyatomicions and diatomics are allcovalent bonds

Covalent Bonds Covalent Bonds

The positive nucleus of one atom

attracts the negative electrons of the

other atom.


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Covalent Bonds

The atoms move closer.

Covalent Bonds

If they get too close, the positive

nuclei repel each other.

Covalent Bonds

There is a balance point where theattraction and the repulsion cancel

out.

Covalent Bonds

Atoms will stay at this balance point.

They have a stable bond.

They are a molecule.

Covalent BondsAtoms in a covalent bond dont

give away electrons or take them

from other atoms.

In a covalent bond, atoms share

electrons.

F F

Both atoms want one more electron.

Covalent Bonds


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F F

They can share these two.

Covalent Bonds

F F

Now both atoms are happy.

Covalent Bonds

F F

This atom has eight outer electrons.

Covalent Bonds

F F

So does this one.

Covalent Bonds

F F

A dot diagram for a molecule is

called a Lewis structure

Covalent Bonds

F-F

The pair of shared electrons

can be drawn as a line.

Covalent Bonds


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O O

Oxygen wants two more electrons.

Covalent Bonds

O O

Theyll share this pair...

Covalent Bonds

O O

and this pair.

Covalent Bonds

O O

Oxygen atoms share two pairs

of electrons.

Covalent Bonds

O O

Again, both atoms seem like they

have eight outer electrons.

Covalent Bonds

O O

Again, both atoms seem like they

have eight outer electrons.

Covalent Bonds


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O=O

They have a double bond, which can

be drawn as two lines.

Covalent Bonds

N N

Nitrogen wants three more electrons.

Covalent Bonds

N N

Nitrogen wants three more electrons.

Covalent Bonds

N N

A nitrogen molecule has a

triple bond.

Covalent Bonds

NN

A nitrogen molecule has a

triple bond.

Covalent Bonds

H

Hydrogen often forms covalent

bonds with other elements.

Covalent Bonds


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H O H



Covalent Bonds

H O H



Covalent Bonds

H-O-H



Covalent Bonds Covalent Bonds

Covalent BondingSYM ASYM

spatial spin

ASYM SYM

spatial spin

space-symmetric tend to be closer

when electrons are sharedequally

NONPOLARCOVALENT BONDS

H2 or Cl2


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when electrons are sharedbut shared unequally

POLAR COVALENT

BONDS

H2O - water is a polar moleculebecause oxygen is moreelectronegative than hydrogen, and therefore electronsare pulled closer to oxygen.

Draw the Lewis structure for the molecule

PH3

You try some!


H-P-H

H

You try some!


H2S

You try some!Draw the Lewis structure for the molecule

H-S-H

You try some!


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HCl

You try some!


H-Cl

You try some!


CCl4

You try some!


Cl

Cl-C-ClCl

You try some!


SiH4

You try some!Draw the Lewis structure for the molecule

H

H-Si-H

H

You try some!


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Hydrogen Chloride

After bonding, the chlorine atom is now in contact

with eight electrons in its highest energy level causingit to become stable

The hydrogen atom is now in contact with two

electrons in its highest energy level resulting in the

hydrogen also being stable

Bonds

Atoms may form multiple covalent bonds that is, share notjust one pair of electrons but two or more pairs

Atoms of different elements will form either one, two, three or

four covalent bonds with other atoms there is a quick way to

work out how many covalent bonds an element will form

The number of covalent bonds is equal to eight minus thegroup number

Group 4 Group 5 Group 6 Group 7

Example Carbon Nitrogen Oxygen Chlorine

Number of

bonds8 4 = 4 8 5 = 3 8 6 = 2 8 7 = 1

Models

Element FormulaChemical

Structure

Ball & Stick

Model

Hydrogen H2

Water H2O

Ammonia NH3

Methane CH4

Double & Triple Bonds Molecules can have a double covalent bonds, meaning they

have two shared pairs of electrons (shown by a double line)

Molecules can also have triple covalent bonds, meaning they

have three shared pairs of electrons (shown by a triple line)

A molecule of oxygen (O2) consists of two oxygen atoms

held together by a double bond

A molecule of nitrogen (N2) has two nitrogen atoms held

together by a triple bond

O O

N N

Elements & Compounds Draw dot and cross diagrams for the following: -

Hydrogen (H2)

Oxygen (O2)

Chlorine (Cl2)

Water (H2O)

Ammonia (NH3)

Hydrogen chloride (HCl)

Methane (CH4)

Elements

Hydrogen atoms can

each form one

covalent bond

One pair of electrons

is shared in a

hydrogen molecule

(H2)

Chlorine atoms can

each form one

covalent bond

One pair of electrons

is shared in a chlorine

molecule (Cl2)

Oxygen atoms can

each form two

covalent bonds

Two pairs of

electrons are shared

in an oxygen

molecule (O2) a

double bond


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Compounds

Hydrogen atoms can

each form one

covalent bond, while

oxygen atoms can

each form two

covalent bonds

Two pairs of


in a water molecule

(H2O)

Hydrogen atoms

and chlorine atoms

can each form one

covalent bond

One pair of

electrons is shared

in a hydrogen

chloride molecule

(HCl)

Hydrogen atoms can

each form one

covalent bond, while

and nitrogen atoms

can each form three

covalent bonds

Three pairs of


in an ammonia

molecule (NH3)

Compounds

Hydrogen atoms can each

form one covalent bond,

while carbon atoms can

each form four covalent

bonds

Four pairs of electrons are

shared in a methane

molecule (CH4)

Quiz 3-METALLIC BONDbond found in metals; holds

metal atoms together very

strongly Formed between atoms of metallic elements

Electron cloud around atoms Good conductors at all states, lustrous, very

high melting points

Examples; Na, Fe, Al, Au, Co

Metals Form AlloysMetals do not combine with metals. They

form Alloys which is a solution of a metal

in a metal.

Examples are steel, brass, bronze and

pewter.

Formula Weights

Formula weight is the sum of the atomic

masses.

Example- CO2

Mass, C + O + O

12.011 + 15.994 + 15.994

43.999


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Practice

Compute the mass of the following compoundsround to nearest tenth & state type of bond:

NaCl;

23 + 35 = 58; Ionic Bond

C2H6;

24 + 6 = 30; Covalent Bond

Na(CO3)2;

23 + 2(12 + 3x16) = 123; Ionic & Covalent

1. Crystalline solids - regular repeating

arrangement of ions in the solid:

2. Ions strongly bonded

Rigid structure

2. High melting points

Coordination number- # of ions of

opposite charge surrounding it

Chapter 3- Crysttal Binding

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