1971-07-27 — Page 17

CIBRARY

UL1971

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CITY HALL

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育教僑華

小學畢業同學

(76)

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Tisk

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LEMEF 中學同學暑期進修專欄堅道英文書院主碥

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(2) 18.70M

(2) Uyu25.

(22)

CHAPTER ONE'.

test 107 hu (20)

574

(26)

物理

(27)

(--)

NUMBERS AND FIGURES

-(28).

ATOMIC PHYSICS

USEFUL NUMBERS

halish

Arabic

129):

4.602 007

130)

English

·Zero

Seventee

Atoms are the smallest particles into which sube

can be disintegrated by mechanical or

Chemica

dense

by orbial neg

Anatom consists of a small.. tively-charged nucleus surrounded

velv-charged electrons,

Bonr Model of Atom:

Each electron orbits round its nucleus in a definite path, and the paths of the electron-

shells around the· are arranged in successive nucleus Taking the four lightest elements for example they have their negatively-charged orbit aj electrons round the positively-charged nucleus

Structure of Atoms)

electro

eut ron

Be

000

One

Three

Four

Lighteen.

#ne teen

Twenty. Thirty

20

40

Forty.

kufry

Sevent.

Winery

Une hundred One thousand

Ten thousand

One hundred

2000 1000

The

thousano

Kunareg, and

fourteen

One million Ten milion

100,000

10,000,000,

(wo hundred and eighty-three,

nunarea apo rry-seven. Three thousan

283

456 1952

ind the

•Hydrogen

thousaño

σπεί

Thirty-four thousane ans hundreth, an

Hellum

Five muhared 480 51a Thousano vei got hundred and: ryenty-one

Fout hundred and

housand

Dinine hundred and thirteen (10) Simion seven hundred and fir

eight thousand six hundred and dinë” one

:(8) 500, 827

(9) €57.913

6.758.

in figures the

Twenty-nine

(2)

Fourty-Lour

(3)

Two hundred and The Li

•·(4) four hundred seventy (5) fight nunar eu and eleven (6) One Cousand and caphteen

(5) (6)

Three mousand t-o nunɑrzu anu

seven thousand nine hunor

and seventy-fiv€

Fifty thousano: Lour

siity thousano three

o punored thous

eignty-nine Five Hundres Banoréo 100

fine mungrua tho

the

SOLUTIONS

chek,

The

Find the sum of 3- SOLUTION The

The requir

C

Shell

The "snells or rings closest to the of an atom can accommodatë a. maximumSON two electrons. Succeeding shells can accommo- dare an increased number of electrons in accor idance with the formulá

2

zn” where ʼn us the number of snells coun! lng from the nucleus

snel containing an electrons is said to be completed or filled. This formula

long With two other simple rules makes it possible to predict the electron, distribution of any ele-

The two rules are

(1) Thengximum number

cectrons in the

outermost shett of an arom can never more than eight

The maximum number of electrons in the next -to-the-outermost shell can never be more than "eighteen

The five atoms as shown in the diagram are all from one group. They are inert gases Their atoms are saturated with electrons that 19. their shells are completed Other stoms nave outer snells which are not completed and these combine esly with orner "uncomp je led*); atoms because two atoms with incomplete obter shells car share the same electrons

Filled Electron Shells

Elements that normally nave eight electrons in their outer shell do not enter into any chemical activity and are said to be inert Thus the condition of eight electrons in the outer shell is a condition

extreme 51004

"If an atom does no have eight electrons in its outermost shell it will try to obrein. this stable condition by entering into some form of chemical combination: Lit possesses eight electrons in

"ils outermost snel.

Thus the chemical activity and properties: of an element are determined by the number of electrons in its outer shell the valence sherl and the electrons are the valence electrons,

Take gold, silver, and copper for instance Gold (Au)

60

BLL) 18(M) 32(N),

Fimited by the rule

18103

未完轉入第張第二頁

nucleons were far apart from each other. This

is because work has been done on the nucleans?

to separate them from each othe, The

difference in poterit sa energy of the nucleons). and the which they would have if separated far apart is camed the binding energy Particles in an atom.

Particles Symbols

Proton

Masse 5

67

24

Charge s

10

coulombs

24

Neutron

67

aum

6 x

coul

1/1840

Helium 2(B)

Neon

2(K) + 8(L)

2(1):

+8(M)

Krypton

Xenon

8(L) 3 B(M)

2(K) + 8(L).

18(N) + 8(0)

18(M)

river (Ag)

18(M) + 19(N)

limited by the rules again) 2(K) • B(L) + 18(M).

•1(0)

CoDder (Cu) 29 = 2(1) = 8(L) ▼ 18{M} » ̄1{NY

All these three elements have only one \ valence electron......... They have che same

lectrical properties and their valency number).

Nucleus

The nucleus consists of some elementary particles the nucleons The nucteons are ne protons and neutrons The nucleons are neld together against the electrostatic repulsion between the protons, neutrons, or between protons and neutrons by a strong nuclear force The potential energy of the nucleons is less than it would be if the

anatomic mass uni

A 7 10

Some terms used with reference to atoms, of]

Mass number (A) -- the number of protons.

and neutron in the nucleus

Atomic number (2)- the number or protons

(3) Isotopes.

in the nucleus.

Nwhere N is the number of

neutrons'

Atoms with their nuclei having. the same number of protons but vito a different number of neutrons

Deuter