2-ch2(atom and element).ppt

8/22/2019 2-Ch2(atom and element).ppt

1/46

1

CHAPTER 2

Read Chapter 2.

Study all examples and complete allexercises.


2/46

2

Chapter 2 Outline

Discovery of the three atomic particles

Isotopes

Periodic Table

Groups and Periods


3/46

ATOMS AND ELEMENTS

3


4/46

4

Origins of the Atomic Theory

John Dalton-1803

Law of Conservation of Matter

Law of Definite Proportions

Water is always H2O not HO

Law of Multiple Proportions

SO2and SO3


5/46

5

Daltons Atomic Theory1. All matter

is composed of atoms.

2. Atoms of an element are alike, atomsof different elements are different.

3. Atoms cannot be created, destroyed,

subdivided, or converted into atoms ofanother element.

4. A compound is formed when differentatoms combine in fixed, simple, whole-

number ratio.5. A chemical change is a rearrangement

of atoms.


6/46

6

Radioactivity One of the pieces of evidence for the

fact that atoms are made of smaller

particles came from the work of

Marie Curie(1876-1934).

She discovered radioactivity, thespontaneous disintegration of some

elements into smaller pieces.

Alpha, a, mass 4 amu, charge +2Beta, b, mass 1/1500 amu, charge -1Gamma, g, no mass, no charge


7/46

7

ATOMIC COMPOSITION

Protons ( p, p+

) + electrical charge

mass = 1.672623 x 10-24 g

relative mass = 1.007 atomic

mass units (amu) Electrons ( e, e-)

negative electrical charge

relative mass = 0.0005 amu

Neutrons ( n, n0)

no electrical charge

mass = 1.009 amu


8/46

8

ATOMCOMPOSITION

Protons and neutrons arein the nucleus.

The number of electronsis equal to the num ber of protons.

Electrons in space around the nucleus.

Atoms are extremely small.One teaspoon of water has 3 timesas many atoms as the AtlanticOcean has teaspoons of water.

The atom is mostly

empty space.


9/46

9

Deflection of a Cathode Ray


10/46

10

Thomsons Charge-to-Mass

Experiment


11/46

11

Millikans Oil DropExperiment


12/46

12

Themodern view of the atom wasdeveloped byErnest Rutherford

(1871-1937).


13/46

13

The RutherfordExperiment


14/46

14

How Large is an Atom?

Circle consists of48 iron atoms.

Radius of circle is

71 Angstrom

units where

1 A = 1 x 10-8 cm.

STM image of quantum corral of ironatoms


15/46

15

Atomic Number, Z

All atoms of the same elementhave the same number of

protons in the nucleus, Z

13

Al

26.9815

atomic number (Z)

symbol

atomic weight


16/46

16

Mass Number, A

C atom with 6 protons and 6 neutrons is themass standard

= 12 atomic mass units, amu

Mass Number = # protons + # neutrons

A Boron atom can have

A = 5 p + 5 n = 10

B105A

Z


17/46

17

Isotopes Atoms of the same element (same Z)

but different mass number (A).

Boron-10 (

10

B) has 5 p and 5 n Boron-11 (11B) has 5 p and 6 n

10B

11B


18/46

18

Check Problems

Determine the mass number of amercury atom with 122 neutrons andgive its complete atomic symbol.

Determine the number of protons,

neutrons, and electrons in a Fe-55 atom.

Hg202

80

26 p+, 26 e-, 29 n


19/46

19

Mass Spectrometer


20/46

20

Isotopes

Because of the existence of isotopes, themass of a collection of atoms has an averagevalue.

Average mass = ATOMIC WEIGHT

Boron is 19.91% 10B and 80.09% 11B. That is,11

B is 80.09 percent abundant on earth. For boron atomic weight (mass)

= 0.1991 (10.01 amu) + 0.8009 (11.01 amu) =10.811 amu

10B

11B

21


21/46

21

Solution

1) abundance atomic mass6Li 7.42% 6.015 amu7Li 92.58% 7.016 amu

What is the atomic weight of Li?(.0742)(6.015 amu) + (.9258)(7.016 amu)

.446313 amu + 6.4954 amu

6.941 amu

22


22/46

22

Practice Problem

Calculate the % abundance for thetwo isotopes of gallium, given Gaatomic weight is 69.723 amu, and:

Ga-69, 68.926 amu;Ga-71, 70.925 amu

23


23/46

23

Solution

2) Calculate the % abundance for the twoisotopes of gallium.

Ga-69, 68.926 amu;

Ga-71, 70.925 amux(68.926 amu) + (1-x)(70.925 amu) = 69.723 amu

68.926 x amu 69.723 amu

-70.925 x amu -70.925 amu-1.999 x amu = -1.202 amu

x = .6013

60.13 %

39.87 %

24


24/46

24

Periodic Table

The periodictable arrangeselementsaccording tosimilar

properties

Dimitri Mendeleev 1868 (1834 - 1907)

(1830 1895)Lothar

Meyer

1869

25


25/46

25

Mendeleevs 1872 PeriodicTable

26


26/46

26

Periods in the Periodic Table

1-7

27


27/46

27

Groups in the Periodic Table

1-18

28


28/46

28

Group 1: Alkali Metals

Cutting sodium metal

Reaction of

potassium and waterK + H2O

29


29/46

29

Group 2: Alkaline Earth Metals

Magnesium

Magnesium

oxide

30


30/46

30

Group 13: B, Al, Ga, In, Tl

Aluminum Boron halides,

BF3& BI3

31


31/46

31

Group 14: C, Si, Ge, Sn, Pb

Quartz, SiO2

Diamond

32


32/46

32

from http://cnst.rice.edu/images

33


33/46

33

Allotropes of Carbon

Graphite

Diamond

Buckyballs

34


34/46

34

Group 15: N, P, As, Sb, Bi

White and redPhosphorus

Ammonia,NH3

35


35/46

35

Group 16: O, S, Se, Te, Po

Shuttle main enginesuse H2 and O2

Sulfur

36


36/46

36

Group 17: F, Cl, Br, I, At

37


37/46

37

Group 18:

He, Ne, Ar, Kr, Xe, Rn

Lighter than airballoons

Neon signs

XeOF4

38


38/46

38

Transition Elements

Inner transition elements

lanthanides and actinides Iron in air gives

iron(III) oxide

Transitionelements

39

P ti P bl


39/46

39

Practice Problems The formula for aluminum sulfide

is Al2S3. What is the formula forgallium sulfide?

Ga2S3

What is the symbol and name ofthe element in period three andgroup fifteen?

P phosphorus

What is the group and period foriodine?

Period 5 and Group 17

40


40/46

0

Summary of the Periodic

Table Features1. Name, Symbol, Atomic Number,Atomic Mass.

2. Solid, liquid, gas

41Summary of the Periodic


41/46

Summary of the PeriodicTable Features

3. Divisions: metals vs. nonmetals

groups(families) vs. periods(series)

1 alkali metals transition metals

2 alkaline earth metals inner transition metal(rare earth series)

17 halogens

18 noble gases

(inert or rare gas)

Main Group Elements (Representative Elements)

42

P ti P bl


42/46

Practice Problems

1. Draw atoms of O-16 and O-17.Determine A and Z for each.

2. An atom has 14 p+, 14 e-, and 17 n.

Identify the element and write thecomplete symbol for this atom.

43

P ti P bl A


43/46

Practice Problems Answers

1. O-16 Z = 8, A = 16

O-17 Z = 8, A = 17Protons and neutrons in the nucleus.

Electrons outside the nucleus.

2. 31Si

14

3. a) In, Sr, Na, Ni b) P, At, S, Arc) Ar d) Na e) At f) Ni g) none

h) In, Sr, P, At, S, Na, Ar

44

P ti P bl


44/46

Practice Problems

4. Calculate the atomic weight of Mg

from the following information:

mass % abundance

Mg-24 23.9850 amu 78.99%

Mg-25 24.9858 amu 10.00%

Mg-26 25.9825 amu 11.01%

45

P ti P bl


45/46

Practice Problems5. Thallium metal, whose atomic mass is

204.384 amu, consists of two isotopes, Tl-203 and Tl-205. The isotopic mass of Tl-

203 is 202.972 amu. and the isotopic mass

of Tl-205 is 204.975 amu.

a) Determine the number of protons,

neutrons, and electrons in each isotope.

b) What is the % abundance of eachisotope?

46


46/46

4. 24.31 amu

5. a) Tl-203 81 p, 81 e, 122 nTl-205 81 p, 81 e, 124 n

b) Tl-203 29.5%

Tl-205 70.5%

Practice Problems Answers

2-ch2(atom and element).ppt

Documents