ATOMIC STRUCTUREATOMIC STRUCTURE

Particle

proton

neutron

electron

Charge

+ ve charge

-ve charge

No charge

1

1

nil

Mass

ATOMIC STRUCTUREATOMIC STRUCTURE

the number of protons in an atom

the number of protons and neutrons in an atom

HeHe22

44 Atomic mass

Atomic number

number of electrons = number of protons

Complete the following table in your Complete the following table in your notesnotes

Atomic #Atomic # Mass #Mass # # of # of ProtonsProtons

# of # of NeutronsNeutrons

# of # of ElectronsElectrons

99 1010

1414 1515

4747 2222

5555 2525

IsotopesIsotopes

Atoms that have the same number of protons but Atoms that have the same number of protons but different numbers of neutronsdifferent numbers of neutrons

Different mass numbersDifferent mass numbers Chemically alike because they have identical Chemically alike because they have identical

numbers for the characteristic chemical behavior numbers for the characteristic chemical behavior of each elementof each element

Ex: Three known isotopes for HEx: Three known isotopes for H– Hydrogen (no neutrons, mass # of 1)Hydrogen (no neutrons, mass # of 1)– Deuterium (one neutron, mass # of 2)Deuterium (one neutron, mass # of 2)– Tritium (two neutrons, mass # of 3)Tritium (two neutrons, mass # of 3)

Your turn…Your turn…

Two of the isotopes for Carbon are Carbon-12 and Two of the isotopes for Carbon are Carbon-12 and Carbon-13, write the chemical symbol for bothCarbon-13, write the chemical symbol for both– 66CC1212

– 66CC1313

Three isotopes for Oxygen are oxygen-16, Three isotopes for Oxygen are oxygen-16, oxygen-17, and oxygen-18, write the chemical oxygen-17, and oxygen-18, write the chemical symbol for all threesymbol for all three– 88OO1616

– 88OO1717

– 88OO1818

Calculating Average Atomic Mass of Calculating Average Atomic Mass of IsotopesIsotopes

In nature, isotopes occur in various In nature, isotopes occur in various percentagespercentages

In order to figure out the average mass of In order to figure out the average mass of each element the percent abundance and each element the percent abundance and mass of each isotope need to be consideredmass of each isotope need to be considered

We can calculate average atomic mass in We can calculate average atomic mass in much the same way as we calculate your much the same way as we calculate your grade in this class…grade in this class…

What are the different categories What are the different categories that you are graded on in this class?that you are graded on in this class? Classwork: 79%Classwork: 79% Practice: 7%Practice: 7% Final: 14%Final: 14% What would your semester grade be if you What would your semester grade be if you

received an 80% for classwork, 50% for practice, received an 80% for classwork, 50% for practice, and 72% on your final?and 72% on your final?– 0.80 x 79 = 63.20.80 x 79 = 63.2– 0.50 x 7 = 3.50.50 x 7 = 3.5– 0.72 x 14 = 10.10.72 x 14 = 10.1– Add all answers together to get % semester grade: Add all answers together to get % semester grade:

63.2 + 3.5 + 10.1 = 76.8 % (a C)63.2 + 3.5 + 10.1 = 76.8 % (a C)

Now lets try with an element!Now lets try with an element!

Copper has two isotopes: copper-63 and Copper has two isotopes: copper-63 and copper-65. The relative abundances of copper-65. The relative abundances of these isotopes are 69.2% and 30.8% these isotopes are 69.2% and 30.8% respectively. Calculate the average atomic respectively. Calculate the average atomic mass of copper.mass of copper.0.692 x 63 = 43.600.692 x 63 = 43.60

0.308 x 65 = 20.020.308 x 65 = 20.02

43.6 + 20.02 = 63.6243.6 + 20.02 = 63.62

One more example…One more example…

Uranium has three naturally occurring Uranium has three naturally occurring isotopes with the following percent isotopes with the following percent abundances: U-234 (0.0058%), U-235 abundances: U-234 (0.0058%), U-235 (0.71%), and U-238 (99.23%). (0.71%), and U-238 (99.23%). – What do you expect the average atomic mass What do you expect the average atomic mass

to be and why?to be and why?– What is the average atomic mass?What is the average atomic mass?

237.85237.85

ATOMIC STRUCTUREATOMIC STRUCTURE

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

SUMMARYSUMMARY

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.

ATOMIC STRUCTUREATOMIC STRUCTURE

There are two ways to represent the atomic

structure of an element or compound;

1. Electronic Configuration

2. Dot & Cross Diagrams

ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION

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 shell

5 in 2nd shell

configuration = 2 , 5

2 + 5 = 7

ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION

Write the electronic configuration for the following elements;

Ca O

Cl Si

Na20

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

DOT & CROSS DIAGRAMSDOT & 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;

Nitrogen N XX X

X

XX

X

N7

14

DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMS

Draw the Dot & Cross diagrams for the following elements;

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

X

X

X

X