CHEM 121

Chapter 2

Winter 2015

1

Elements and Symbols• Elements:• •

• Chemical symbols• •

• Ex. cobalt =

nitrogen =

2

Elements• Ordered by atomic number• “Periodic” trends• Periodic table by Mendeleev (1871)

1A 2A

3B 4B 5B 6B 7B 8B 1B 2B

3A 4A 5A 6A 7A

8A

3

Some unusual element symbols

• Au

• Ag

• Fe

• Pb

• Cu

4

• Sn

• K

• Na

Reading the Periodic Table

Period: Group:

Alkali metals:

Alkaline earth metals:

Halogens:

5

Noble Gases:

Metals, Nonmetals, and Metalloids

• Metals:• • •

• Nonmetals:• • •

• Metalloids:• B, Si, Ge, As, Sb, Te, At

6

CarbonThree elemental formsInteresting bonding with many elements

7

Diamond Graphite Buckyball

Element Song• Meet the elements: http://www.youtube.com/watch?v=Uy0m7jnyv6U&feature=related

• All of the elements: http://www.youtube.com/watch?v=zGM-wSKFBpo&feature=related

8

Elements of Life

9

C N O H

Other life elements

Fluids:

Na

K

Cl

10

Major minerals (macronutrients)

Proteins:

Mg

S

Teeth & Bone:

Ca

P

Trace elements (micronutrients)

Fe Zn I F Se

Molecules

Molecules:Compounds:

Chemical formula:

How many atoms? •NaCl

•H2O

•CsCl2•H2O2

•Ca(OH)211

How many of each type of atom is in one molecule of ammonium phosphate?

12

3-minute practice

Atoms and Subatomic Particles

Proton Neutron Electron

Diameter of one atom: 0.1 – 0.5 nm

13amu: atomic mass unit (1/12 C atom mass)

Charge

Mass (g)

Mass (amu)

Location

Atomic Number and Mass Number

• Atomic Number (Z)

14

• Atoms are electrically neutral

• Mass Number (A)

How many protons, electrons, and neutrons are in each of the following:

•Z = 14 A= 29

•An atom with a nucleus with 4 protons and 5 neutrons?

•A potassium atom with a mass number of 39?

15

3-minute practice

IsotopesIsotopes:

16

Mg

12

24

Atomic Symbol

Isotopes of Carbon12C : 6 protons + 6 neutrons13C : 6 protons + 7 neutrons14C : 6 protons + 8 neutrons

17

98.89 %1.11 %

<0.01 %

All have nearly identical chemical behavior

How many protons, neutrons and electrons does each of the following have?

• 35Cl

• 37Cl

• C-14

18

3-minute practice

Atomic Mass

weighted average of masses of all the naturally occurring isotopes of that element

19

Example: chlorine

35Cl

37Cl

Mass (amu)

x Abundance (%)

Contribution to

average Cl atom

=

x

x

100

78.75

100

22.24

=

=

Relative Masses of Atoms

Atoms are too small to measure actual mass

Compare masses of atoms using relative mass

20

An average Zn atom is ~ 3x more massive than an average Na atom

Medical Use of Isotopes

I-131

21

Reading the Periodic TablePeriod: horizontal row Group: vertical column

Elements in the same group have similar chemical propertiesbecause they have the same number of outer shell e-

22

Each e- in an atom “sits” at an energy level (n)• •

•

• •

Energy States• Ground state:

• n = 1

• Excited states: • n = 2, 3, 4,…

• Photon emitted:

• Photon absorbed:

23

Energy Sublevels

• Each level consists of sublevels• # of sublevels in each level = level

number

• n = 1

• n = 2

• n = 3

• n = 4

24

Increasing energy of sublevels within an energy level:

Disneyland Analogy

25

Orbitals

• Regions with the highest probability of finding an electron

• Each type of orbital has a given shape:

26

s orbital

p orbitals

Orbitals

27

d orbitals

Each orbital can hold _____ electrons• s orbitals:

• p orbitals:

• d orbitals:

Orbitalsf orbitals

http://int.ch.liv.ac.uk/Lanthanide/Ln_Chemistry_folder/Miscellaneous%20folder/Miscellaneous.html#f_orbitals 28

• How many sublevels are in the n = 3 energy level?

• What are these sublevels? How many of each type are there?

• How many electrons can be held in the n = 3 energy levels?

29

5-minute practice

Orbital Energy Levels• Pauli Exclusion Principle:

•

• Electrons want to sit in lowest energy level

• For a given n value: Order of sublevel energy: s < p < d < f

• Orbital Diagrams

30

1s

Orbital Diagram:

Electron Configurations

31

tell us which orbitals electrons are in for a given atom

Example: Hydrogen Atomic Number: (How many electrons?)

Electron Configuration:

1s

Orbital Diagram:

Electron Configurations

32

Example: Helium Atomic Number: (How many e-?)

Electron Configuration:

1s

Orbital Diagram:

Example: Lithium Atomic Number: (How many e-?)

Electron Configuration:

2s

1s

Orbital Diagram:

Electron Configurations

33

Example: Boron Atomic Number: (How many electrons?)

Electron Configuration:

2s

2p

1s

Orbital Diagram:

Electron Configurations

34

Example: Oxygen Atomic Number: (How many electrons?)

Electron Configuration:

2s

2p

Abbreviated Configuration:

Electron Configurations relate to the Periodic Table!

• s block elements: end with s orbital

Na:

• p block elements: end with p orbitals

P:

• d block elements: end with d orbitals

Ni:

Note: 4s orbital comes before 3d orbital

35

Sublevel Order

36

Write the abbreviated electron configuration for the following:

• K• S• Br• Ar• Cs

37

5-minute review

Periodic Trends

Valence electrons: • • •

38

Boron (B): How many valence electrons?

Chlorine (Cl):

Periodic Trends

39

Aluminium (Al):

How many valence electrons?

How many valence electrons?

Electron Dot Symbols

40

Lithium Valence electrons?

Carbon Valence electrons?

Fluorine Valence electrons?

Draw electron dot symbols for the following:

•Sulfur

•Potassium

•Beryllium

•Silicon

41

5-minute review

Elements• Elements ordered by atomic number• “Periodic” trends• Periodic table by Mendeleev (1871)

1A 2A

3B 4B 5B 6B 7B 8B 1B 2B

3A 4A 5A 6A 7A

8A

42

Atomic radius:

•

•

Atomic Size

43

Ionization:

Ionization Energy

44