Physical Science BHHS 2010/Melmore 1

Learning Objectives

Learning ObjectivesApply an understanding of the structure of the atom. Be able to interpret numbers of subatomic particles making up each atom.

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Atomic ModelsThis model of the

atom may look familiar to you. This is the Bohr model. In this model, the nucleus is orbited by electrons, which are in different energy levels. A model uses familiar ideas

to explain unfamiliar facts observed in nature. A model can be changed as

new information is collected.

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ATOMIC STRUCTUREATOMIC STRUCTURE

Particle

proton

neutron

electron

Charge

+ ve charge

-ve charge

No charge

1

1

nil

Mass

Atoms are the smallest particles of an element that retains the chemical properties of that elementParts:

Nucleus – small region in the center of the atom. (+ charged protons, = charged neutrons)

Electron Cloud – large region, compared to nucleus, where electrons are found.

Size of nucleus vs. electron cloudIf an atom was the size of a sports stadium, the

nucleus would be the size of a marble!Subatomic Particles:Protons : + charge, relative mass = 1.007 atomic

mass units (amu); round to 1Neutrons: = charge, relative mass = 1.009

atomic mass units (amu); round to 1Electrons: - charge, relative mass = 0.0005

atomic mass units (amu); round to 0 (not factored in when figuring total mass of an atom)

IsotopesAtoms with the same number of protons &

electrons but a different number of neutrons.They are the same element, but have

different masses.All isotopes are used to calculate atomic

mass (reason why weight is a decimal).

Most elements consist of a mixture of isotopes.

Atomic NumberNumber of protons in the nucleus (also the

number of electrons)Typically the number on top of the symbol on

the Periodic Table.

AlAl

13

26.981

Atomic Number

Mass NumberNumber of protons + number of neutrons in

an atom.When solving for number of neutrons: round

mass number properly, subtract atomic number from mass number.

Mass number is the number of protons and neutrons in the nucleus of an isotope: Mass # = p+ + n0

NuclideNuclide pp++ nn00 ee-- Mass #Mass #

Oxygen Oxygen - - 1010

- - 3333 4242

- - 3131 1515

8 8 1818

Arsenic 75 33 75

Phosphorus 15 3116

Complete SymbolsContain the symbol of the element,

the mass number and the atomic number.

X Massnumber

Atomicnumber

Subscript →

Superscript →

ATOMIC STRUCTUREATOMIC STRUCTURE

the number of protons in an atom

the number of protons and neutrons in an atom

HeHe22

44 Atomic mass

Atomic number

number of electrons = number of protons

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ATOMIC STRUCTUREATOMIC STRUCTURE

Electrons are arranged in Energy Levels

or Shells around the nucleus of an atom.

• first shell a maximum of 2 electrons

• second shell a maximum of 8

electrons

• third shell a maximum of 8

electrons

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Shells

s p d f g Total

1 2 2

2 2 6 8

3 2 6 10 18

4 2 6 10 14 32

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DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMS

With Dot & Cross diagrams elements and

compounds are represented by Dots or Crosses to

show electrons, and circles to show the shells. For

example;

Nitrogen N XX X

X

XX

X

N7

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ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION

With electronic configuration elements are

represented numerically by the number of

electrons in their shells and number of shells. For

example;

N

Nitrogen

7

14

2 in 1st shell

5 in 2nd shell

configuration = 2 , 5

2 + 5 = 7

DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMS

With Dot & Cross diagrams elements and

compounds are represented by Dots or Crosses to

show electrons, and circles to show the shells. For

example;

Nitrogen N XX X

X

XX

X

N7

14

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DOT & CROSS DIAGRAMSDOT & CROSS DIAGRAMS

Draw the Dot & Cross diagrams for the following elements;

O Cl8 17

16 35a) b)

O

X

XX

X

X

X

X

X

Cl

X

X

X

X X

X

XX

X

X

X

X

X

XX

X

X

X

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1. How many protons does Helium have

2. How many electrons does Zinc have

3. Silver has ____electrons

4. Magnesium____electrons

5. Uranium____electrons

6. Kryption ______protons

7. Aluminium____electrons

8. Bromine ____mass

9. Calcium ____electrons

10. Sodium has ______protons

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1. What is meant when an atom is said to be in its ground state?

3. The subatomic particle(s) found in the nucleus of an atom are

5. What is the maximum number of electrons that can occupy an atomic orbital?

8. In which way do isotopes of an element differ?

9. Calcium's atomic number is 20. What does that that tell us about a calcium atom?

10. What is ALWAYS true regarding atoms of two different elements?

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1. What is meant when an atom is said to be in its ground state?CORRECT: The state an atom is found naturally. 3. The subatomic particle(s) found in the nucleus of an atom are

CORRECT: protons and neutrons. 5. What is the maximum number of electrons that can occupy an atomic orbital?

CORRECT: 2, 6, 10, 148. In which way do isotopes of an element differ?

CORRECT: number of neutrons in the atom 9. Calcium's atomic number is 20. What does that that tell us about a calcium atom?

CORRECT: It has 20 protons. 10. What is ALWAYS true regarding atoms of two different elements?

CORRECT: They have different numbers of protons.

ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATION

Write the electronic configuration for the following elements;

Ca O

Cl Si

Na20

40

11

23

8

17

16

35

14

28B

11

5

a) b) c)

d) e) f)

2,8,8,2 2,8,1

2,8,7 2,8,4 2,3

2,6

ELECTRONIC CONFIGURATIONELECTRONIC CONFIGURATIONWrite the name, electronic configuration and diagram for the following elements;

Mg Be

C Si

Ca12

24

20

40

4

6

8

12

14

28

Ge72

32

1) 2) 3)

4) 5) 6)

2,8,2 2,8,8,2

2,4 2,8,4 2,8,18,4

2,2

Ga Al26

B10

7) 8) 9)

2,8,18,3 2,8,3

F Cl18

34

Br79

10)

11) 12)

2,7 2,8,7

69

31 13 5

35179

2,8,18,7

2,3

DO YOU REMEMBER ?DO YOU REMEMBER ?1. The Atomic Number of an

atom is the............

2. The Atomic Mass of an atom is

3. Protons in the nucleus equals the.....

3. The number of Electrons =

4. Electrons orbit the nucleus in _______

= number of protons in the nucleus.

= number of Protons + Neutrons in the nucleus.

= Number of Electrons.

Number of Protons

shells.

Structure of Subatomic ParticlesSubatomic particles composed of fast moving

points of energy called quarksQuark Calculations

(for protons and neutrons)Each proton is 2 up quarks and 1 down quark

2(2/3) – 1(1/3) = 4/3 – 1/3 = 3/3 or +1Each neutron is 2 down quarks and 1 up quark

2(-1/3) + 2/3 = 0Each electron is composed of 2 down quarks

3(-1/3) = -1