Atomic Structure 2 (1)

8/3/2019 Atomic Structure 2 (1)

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Bohrs Atom

electrons in orbits

nucleus


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HELIUM ATOM

+N

N+

--

proton

electron neutron

Shell

What do these particles consist of?


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ATOMIC STRUCTUREEQ: What are the basic properties of elements?

Particle

proton

neutron

electron

Charge

+ ve charge

-ve charge

No charge

1

1

nil

Mass


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the number of protons inan atom

the number ofprotons and

neutrons in anatom

He

2

4 Atomic mass

Atomic number

number of electrons = number of protons


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Electrons are arranged in Energy Levels or

Shells around the nucleus of an atom.

first shell a maximum of 2 electrons

second shell a maximum of 8 electrons

third shell a maximum of 8 electrons


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There are two ways to represent the atomic

structure of an element or compound;

1. Electronic Configuration

2. Dot & Cross Diagrams


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ELECTRONIC CONFIGURATIONEQ: What are the basic properties of elements?

With electronic configuration elements are represented

numerically by the number of electrons in their shells

and number of shells. For example;

N

Nitrogen

7

14

2 in 1st

shell5 in 2nd shell

configuration = 2 , 5

2 + 5 = 7


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ELECTRONIC CONFIGURATION

Write the electronic configuration for the followingelements;

Ca O

Cl Si

Na

20

40

11

23

8

17

16

35

14

28B 11

5

a) b) c)

d) e) f)

2,8,8,2 2,8,1

2,8,7 2,8,4 2,3

2,6


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DOT & CROSS DIAGRAMS

With Dot & Cross diagrams elements and compounds

are represented by Dots or Crosses to show electrons,

and circles to show the shells. For example;

NitrogenN

XX X

X

XX

X

N7

14


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DOT & CROSS DIAGRAMS

Draw the Dot & Cross diagrams for the followingelements;

O Cl8 17

16 35a) b)

O

X

XX

X

X

X

X

X

Cl

X

X

X

X X

X

XX

X

X

X

X

X

XX

X

X

X


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SUMMARY

1. The Atomic Number of an atom = number of

protons in the nucleus.

2. The Atomic Mass of an atom = number of

Protons + Neutrons in the nucleus.

3. The number of Protons = Number of Electrons.

4. Electrons orbit the nucleus in shells.

5. Each shell can only carry a set number of electrons.


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Types of BondsEQ: What are the basic properties of elements?

What is the difference between acompound and a molecule?A compound - two or more different

elements bonded together

A molecule - two or more elements

bonded together by a covalent bond

Identify the following as a compound,

molecule, or both


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Na+Cl-

H2O

CO2


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Na+Cl- compound

H2O

CO2


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Na+Cl- compound

H2O both

CO2


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Na+Cl- compound

H2O both

CO2 both


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Types of bondsEQ: What are the basic properties of elements?

Ionic- bonding that results in thetransfer of electrons from one elementto another

Covalent bond- bonding that results inthe sharing of electrons; each bondequals two electrons

Hydrogen bonding- occurs betweenpolar compounds and H; this is an

attraction


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2.2 Properties of Water


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EQ: What are the important characteristics that make essential for life?

The water molecule is a polarmolecule: The opposite ends haveopposite charges

Polarity allows water molecules to

form hydrogen bonds with eachother


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2.2 Properties of Water


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Four of waters properties that

facilitate an environment for life

are:

Cohesive behavior

High specific heat

Expansion upon freezing

Versatility as a solvent

C h i


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Cohesion

-the attraction of water molecules to eachother

-occurs due to H-bonding

Adhesion-an attraction between differentsubstances, for example, between

water and plant cell wallsWhat organisms benefit from these

properties?Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Fig. 3-3


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g

Water-conductingcells

Adhesion

Cohesion150 m

Directionof water

movement


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is a measure of how hard it is tobreak the surface of a liquid

Surface tension is related tocohesion

What kind of organisms benefit fromthis property?

Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Surface TensionEQ: What are the important characteristics that makeessential for life?

Fig. 3-4


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g


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Acids and BasesEQ: What are the important characteristics that make essential for life?

An acid is any substance thatincreases the H+ concentration of a

solution

A base is any substance thatreduces the H+ concentration of a

solution



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The pH ScaleEQ: What are the important characteristics that make essential for life?

In any aqueous solution at 25C the productof H+ and OH is constant and can be writtenas

[H+][OH] = 1014

The pH of a solution is defined by thenegative logarithm of H+ concentration,written as

pH =log [H+]

What is the [H+] of a neutral solution?[H+] is 107 = (7) = 7



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What is the pH of a solution thathas a [H+] of 10(-6)

pH= 6

What is the pOH of the samesolution?

pOH= 8


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Acidic solutions have pH values lessthan 7

Basic solutions have pH values greater

than 7 Most biological fluids have pH values in

the range of 6 to 8

Which solution has more [H+], asolution with a pH of 6 or pH of 8. How

many?


Fig. 3-UN5

0


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Bases donate OH

or accept H+ inaqueous solutions

Acids donate H+

inaqueous solutionsAcidic[H+] > [OH]

Neutral[H+] = [OH]

Basic[H+] < [OH]

14

7

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Atomic Structure 2 (1)

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