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How many electrons, protons, and neutrons does Uranium have?

LecturePLUS Timberlake


Atomic Theory

Atoms are building blocks of elements

Similar atoms in each element

Different from atoms of other elements

Two or more different atoms bond in

simple ratios to form compoundsLecturePLUS Timberlake

Subatomic Particles

Particle Symbol Charge Relative

Mass

Electron e- 1- 0

Proton p+ + 1

Neutron n 0 1LecturePLUS Timberlake

Location of Subatomic Particles

10-13 cm

electrons

protons

neutrons

10-8 cmLecturePLUS Timberlake

nucleus

Atomic Number

Counts the number

of

protons

in an atom


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


Periodic Table

1 2 3 4 5 6 7 8


11 Na

Atomic Number on the Periodic Table

11

NaLecturePLUS Timberlake

Atomic Number

Symbol

All atoms of an element have the same number of

protons

11

NaLecturePLUS Timberlake

11 protons

Sodium

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


C. Barium



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 LecturePLUS Timberlake

Number of Electrons

An atom is neutral

The net charge is zero

Number of protons = Number of electrons

Atomic number = Number of electrons


Mass Number

Counts the number

of

protons and neutrons

in an atom


Atomic Symbols

Show the mass number and atomic

number

Give the symbol of the element

mass number

23 Na sodium-23

atomic number 11 LecturePLUS Timberlake

More Atomic Symbols

16 31 65

O P Zn

8 15 30

8 p+ 15 p+ 30 p+

8 n 16 n 35 n

8 e- 15 e- 30 e-


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 - 37LecturePLUS Timberlake

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 _______ _______ _______ LecturePLUS Timberlake

Solution AT 2

12C 13C 14C 6 6 6

#P __6___ _ 6___ ___6___

#N __6___ _ _7___ ___8___

#E __6___ _ 6___ ___6___


Learning Check AT 3An 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) 67LecturePLUS Timberlake

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) 67LecturePLUS Timberlake

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- ___________


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


Learning Check AT 5An atom has 14 protons and 20 neutrons.

A. Its atomic number is

1) 14 2) 16 3) 34

B. Its mass number is

1) 14 2) 16 3) 34

C. The element is

1) Si 2) Ca 3) Se

D. Another isotope of this element is

1) 34X 2) 34X 3) 36X

16 14 14


Solution AT 5An atom has 14 protons and 20 neutrons.

A. It has atomic number

1) 14

B. It has a mass number of

3) 34

C. The element is

1) Si

D. Another isotope of this element would be

3) 36X

14 LecturePLUS Timberlake

Do Now

Complete Do Now Worksheet and please include the question below on to your worksheet.

What is an Isotope?


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.


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

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 __________


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__


Calculating Atomic Mass

Percent(%) abundance of isotopes

Mass of each isotope of that element

Weighted average =

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

…

100 100


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

Learning Check AT7

Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the atomic mass of gallium?


AT 7Isotope Mas

s% Convert

PercentageMultiply

Mass with %

Mass by %

Gallium - 69

68.9

60.2%

60.2/100= .602

68.9 x .602=

41.5 amu

Gallium - 71

70.9

39.8%

39.8/100= .398

70.9 x .398=

28.2 amu


Now we add the masses of both isotopes to get the Average Atomic Mass.

41.5 amu + 28.2 amu = 69.7 amu

Average Atomic Mass of Ga = 69.7 amu

Let’s Practice

Look at Question 1 on your practice handout.


Finding An Isotopic Mass

A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope?


Assign X and Y values:

X = 10B =10 amu Y = 11B =11 amu

Determine Y in terms of X

X + Y = 100% or 1.0

In this case we will use 1.0 to represent 100%

X + Y = 1.0

Subtract X in order to solve for Y

Y = 1.0 - XLecturePLUS Timberlake

Now we will solve for X:

X + Y = 10.8 Average atomic mass of Boron

Insert the mass for X and Y

(10)X + (11) (1.0 – X) = 10.8

10X + 11 – 11X = 10.8

10X - 11X = 10.8 – 11

-1X = - .20 Multiply by -1 to get rid of the negative

X = .20

Multiply by 100% to get percentage

X = .20 x 100% = 20%LecturePLUS Timberlake

So if X = 20%

Then Y = 80%

How:

X + Y = 100%

Y = 100% - X

Y= 100% - 20%

Y = 80%

So Boron–10 = 20% and Boron-11= 80% LecturePLUS Timberlake

Learning Check AT8

Copper has two isotopes 63Cu (62.9 amu) and 65Cu (64.9 amu). What is the % abundance of each isotope? (Hint: Check periodic table for atomic mass)


Solution AT8

Copper–63= 70%

Copper–65= 30%


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