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Definition:

Atom of same element with same proton number

but different nucleon numbers.

@ atom of an element with different number ofneutrons (text book).

Eg: questions 2 in page 21

Characteristic:

Isotope of an element have same chemical properties

but different physical prop (eg: densities & melting point).

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Isotope Proton

number

Nucleon

number

Number

of

protons

Number

of

neutrons

16

Oxygen-16 O8

8 16 8 8

17

Oxygen-16 O8

8 17 8 9

18

Oxygen-16 O8

8 18 8 10

35

Chlorine-35 Cl17

17 35 17 18

37

Chlorine-35 Cl17

17 37 17 20

Element

Oxygen

Chlorine

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Isotope Proton

number

Nucleon

number

Number

of

protons

Number

of

neutrons

1

Hydrogen-1 H1

1 1 1 0

2

Hydrogen-2 H1

1 2 1 1

3

Hydrogen-3 H1

1 3 1 2

80

Bromine-80 Br35

35 80 35 45

81

Bromine-81 Br35

35 81 35 46

Element

Hydrogen

Bromine

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Isotope Proton

number

Nucleon

number

Number

of

protons

Number

of

neutrons

12

Carbon-12 C6

6 12 6 6

13

Carbon-13 C6

6 13 6 7

14

Carbon-14 C6

6 14 6 8

Element

Carbon

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Field Isotope applications

Medical gamma rays of cobalt-60 used to kill cancer cells

without surgery the patient.

steril the medical instrument.

Radioactive like iodine-131 used to detect malfunction

of thyroid gland.

Archeology Radioisotope carbon-14 used to study age of ancientartifacts (bhn2 purba)

Agricultural carbon-14 is used to study passage of carbon in

photosynthesis.

Industrial sodium-24 used to detect leakage (kebocoran) of

underground pipe

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Atoms made up of :

nucleus that contain protons & neutrons

electrons that move in shells around

nucleus

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Shells of an atom is numbered starting from shells that closest to nucleus.

Shells closest to nucleus numbered with one.

Next shells is numbered with two & so on..

Each shells can only consists of a certain number of electrons.

The ways electrons distributed @ arranged in shells of an atom is called electronarrangement @ electron configuration.

First shell

Second shell

Third shell

Max no. of e for elements with proton number 1-20

Nucleus

8

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1. Fill electrons to the shells that closet to nucleus first which is 1st shell

with max number of electrons that 1st

shells can hold.

2. The next shells is filled up (diisi) if there are remaining of electrons.

Eg: Calcium, Ca has 20 electrons (20 protons)

electron arrangement of calcium is 2.8.8.2

CaCa

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Valence electrons:

are electrons in the outermost shell of an atom

eg: electron arrangement of calcium is 2.8.8.2

Thus, it has two valence electrons.

element with same number of valence electrons

have same chemical properties.

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1. What mean by isotope?

Atom of same element with same proton number but different

nucleon numbers.

@ atom of an element with different number of neutrons

32 31

2. P and P are two isotopes of phosphorus. State the number of subatomic15 15

particles for each isotopes.

Isotope Proton

number

Nucleon

number

Number of

protons

Number of

neutrons

32

P15

15 32 15 17

31

P15

15 31 15 16

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3. Write the electron arrangement for the atoms below.

35

a) Cl17

19

b) F9

4. Determine the number of valence electrons for elements with this proton number:a) 7

b) 9

c) 16