1

The Atom

Atomic Number and Mass,

Isotopes

2

Elements

Pure substances that cannot be separated into different substances by ordinary processes

Are the building blocks of matter

112 elements known todayExamples: carbon

goldcalcium

3

Symbols of Elements

Use 1 or 2 letter abbreviations Capitalize the first letter only

Examples:

C carbon Co cobalt

N nitrogen Ca calcium

F fluorine Br bromine O oxygen Mg

magnesium

4

Symbols from Latin Names

Element Symbol Latin name

Copper Cu cuprum

Gold Au aurum

Lead Pb plumbum

Mercury Hg hydrargyrum

Potassium K kalium

Silver Ag argentum

Sodium Na natrium

Tin Sn stannum

5

% Major Elements in the Body

O 65.0 % K 0.34

C 18.0 S 0.26

H 10.0 Na 0.14

N 3.0 Cl 0.14

Ca 1.4 Fe 0.004

P 1.0 Zn 0.003

Mg 0.50

Trace Elements

As, Cr, Co, Cu, F, I, Mn, Mo, Ni, Se, Si, V

6

Learning Check

Select the correct symbol for each:

A. Calcium

1) C 2) Ca 3) CA

B. Sulfur

1) S 2) Sl 3) Su

C. Iron

1) Ir 2) FE 3) Fe

7

Solution

Select the correct symbol for each:

A. Calcium

2) Ca

B. Sulfur

1) S

C. Iron

3) Fe

8

Learning Check

Select the correct name for each:

A. N

1) neon 2) nitrogen 3) nickelB. P

1) potassium 2) phogiston3) phosphorus

C. Ag

1) silver 2) agean 3) gold

9

Solution

Select the correct name for each:

A. N

2) nitrogen B. P

3) phosphorus

C. Ag

1) silver

10

Periodic Table

Represents physical and chemical

behavior of elements

Arranges elements by increasing atomic

number

Repeats similar properties in columns

known as chemical families or groups

11

Subatomic Particles

Particle Symbol Charge RelativeMass

Electron e- 1- 0

Proton p+ + 1

Neutron n 0 1

12

Location of Subatomic Particles

10-13 cm

electrons

protons

neutrons

10-8 cm

nucleus

13

Atomic Number

Counts the number

of

protons

in an atom

14

Periodic Table

1 2 3 4 5 6 7 8

11 Na

15

Atomic Number on the Periodic Table

11

Na

Atomic Number

Symbol

16

All atoms of an element have the same number of protons

11

Na

11 protons

Sodium

17

Learning Check AT 1

State the number of protons for atoms of each of the following:

A. Nitrogen

1) 5 protons 2) 7 protons 3) 14 protons

B. Sulfur

1) 32 protons 2) 16 protons 3) 6 protons

C. Barium

1) 137 protons 2) 81 protons 3) 56 protons

18

Solution AT 1

State the number of protons for atoms of each of the following:

A. Nitrogen

2) 7 protons

B. Sulfur

2) 16 protons

C. Barium

3) 56 protons

19

Number of Electrons

An atom is neutral The net charge is zeroNumber of protons = Number of electronsAtomic number = Number of electrons

20

Mass Number

Counts the number

of

protons and neutrons

in an atom

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Atomic Symbols

Show the mass number and atomic number

Give the symbol of the element

mass number

23 Na sodium-23

atomic number 11

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More Atomic Symbols

16 31 65

O P Zn

8 15 30

8 p+ 15 p+ 30 p+

8 n 16 n 35 n8 e- 15 e- 30 e-

23

Isotopes

Atoms with the same number of protons,

but different numbers of neutrons.

Atoms of the same element (same atomic

number) with different mass numbers

Isotopes of chlorine

35Cl 37Cl17 17

chlorine - 35 chlorine - 37

24

Learning Check AT 2

Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.

12C 13C 14C 6 6 6

#P _______ _______ _______

#N _______ _______ _______

#E _______ _______ _______

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Solution AT 2

12C 13C 14C 6 6 6

#P __6___ _ 6___ ___6___

#N __6___ _ _7___ ___8___

#E __6___ _ 6___ ___6___

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Learning Check AT 3

An atom of zinc has a mass number of 65.

A. Number of protons in the zinc atom

1) 30 2) 35 3) 65

B. Number of neutrons in the zinc atom

1) 30 2) 35 3) 65

C. What is the mass number of a zinc isotope

with 37 neutrons?

1) 37 2) 65 3) 67

27

Solution AT 3

An atom of zinc has a mass number of 65.

A. Number of protons in the zinc atom

1) 30

B. Number of neutrons in the zinc atom

2) 35

C. What is the mass number of a zinc isotope

with 37 neutrons?

3) 67

28

Learning Check AT 4

Write the atomic symbols for atoms with the following:

A. 8 p+, 8 n, 8 e- ___________

B. 17p+, 20n, 17e- ___________

C. 47p+, 60 n, 47 e- ___________

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Solution AT 4

16OA. 8 p+, 8 n, 8 e- 8

B. 17p+, 20n, 17e- 37Cl 17

C. 47p+, 60 n, 47 e- 107Ag 47

30

Learning Check AT 5

An atom has 14 protons and 20 neutrons.A. Its atomic number is

1) 14 2) 16 3) 34

B. Its mass number is1) 14 2) 16 3) 34

C. The element is1) Si 2) Ca 3) Se

D. Another isotope of this element is

1) 34X 2) 34X 3) 36X 16 14 14

31

Solution AT 5

An atom has 14 protons and 20 neutrons.A. It has atomic number

1) 14

B. It has a mass number of3) 34

C. The element is1) Si

D. Another isotope of this element would be

3) 36X 14

32

Masses of Atoms

A scale designed for atoms gives their small

atomic masses in atomic mass units (amu)

An atom of 12C was assigned an exact mass of

12.00 amu

Relative masses of all other atoms was

determined by comparing each to the mass of 12C

An atom twice as heavy has a mass of 24.00

amu. An atom half as heavy is 6.00 amu.

33

Atomic Mass

Listed on the periodic table

Gives the mass of “average” atom of each

element compared to 12C

Average atom based on all the isotopes and their

abundance %

Atomic mass is not a whole number

Na22.99

34

Learning Check AT6

Using the periodic table, specify the atomic mass of each element (round to the tenths place):

A. calcium __________

B. aluminum __________

C. lead __________

D. barium __________

E. iron __________

35

Solution AT6

Using the periodic table, specify the atomic mass of each element (round to the tenths place):

A. calcium _40.1 amu _

B. aluminum _27.0 amu _

C. lead _207.2 amu_

D. barium _137.3 amu_

E. iron _55.8 amu__

36

Calculating Atomic Mass

Percent(%) abundance of isotopes

Mass of each isotope of that element

Weighted average =

mass isotope1(%) + mass isotope2(%) + …

100 100

37

Atomic Mass of Magnesium

Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70%

25Mg = 25.0 amu 10.13%

26Mg = 26.0 amu 11.17%

Atomic mass (average mass) Mg = 24.3 amu

Mg24.3