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Unit 1 Matter and Bonding. CHEMISTRY. Why do I have to study chemistry?. Atomic Theory. All elements are composed of atoms Each element contains similar atoms Atoms of one element are different from ones from another Two or more different atoms bond together to form a compound.

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Unit 1 matter and bonding

Unit 1Matter and Bonding



Why do I have to study chemistry?

Atomic theory
Atomic Theory

  • All elements are composed of atoms

  • Each element contains similar atoms

  • Atoms of one element are different from ones from another

  • Two or more different atoms bond together to form a compound

Subatomic particles
Subatomic Particles

Particle Symbol Charge Relative

Mass (u)

Electron e- -1 ~0

Proton p+ +1 1

Neutron n 0 1

Location of subatomic particles
Location of Subatomic Particles

10-15 m




10-10 m


Characteristics of electrons
Characteristics of Electrons

  • Extremely small mass

  • Located outside the nucleus

  • Moving at extremely high speeds in defined areas around the nucleus called orbitals

  • Have specific energy levels

  • In a neutral atom the # of electrons equals the # of protons


  • Are pure substances that cannot be separated into different substances by ordinary processes

  • Are the building blocks of matter

  • All atoms of an element have the same number of protons

  • 118 elements known today

    Examples: carbon



Liquid nitrogen.

Name the element found in each
Name the element found in each!

1. Carbon 2. Sodium 3. Aluminum

  • 2.

4. Copper 5. Sulfur 6. Iodine

Symbols of elements
Symbols of Elements

  • Use 1 or 2 letter abbreviations

  • Capitalize the first letter only


    C carbon Co cobalt

    P Phosphorus Ca calcium

    Ba Barium Mg magnesium

Symbols from latin names
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

Diatomic elements

Some elements are composed of two atoms bonded together

Whenever you write the symbol for these elements a subscript must be written

Oxygen O2

Nitrogen N2

Chlorine Cl2

Iodine I2

Diatomic elements

The periodic table
The 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

Groups of elements
Groups of Elements

  • Vertical columns on the periodic table

  • Similar physical properties

  • Similar chemical properties

Representative groups
Representative Groups

  • Group 1 Alkali Metals

  • Group 2 Alkaline Earth Metals

  • Group 17 Halogens

  • Group 18 Noble Gases

Periods on the periodic table
Periods on the Periodic Table

  • Horizontal rows from Group 1 to Group 18.

  • Numbered 1, 2, 3, ….

Metals general properties
Metals- General properties

  • Located on the left hand side

  • Usually solids

  • Lustrous, ductile, malleable

  • Good conductors of heat and electricity

  • Group 1 and 2 metals react with oxygen to form metal oxides which can react with water to from bases (alkaline)

  • Transition metals vary in reactivity, typically hard, high melting points, good conductors of electricity, form ions of variable charge

Non metals general properties
Non-metals: General properties

  • Located on the right hand side

  • Can be solid (S, P,C) liquid (Br2 at room temperature) or gaseous (O2, F2)

  • Dull and brittle solids

  • Poor conductors, good insulators

  • Halogens are extremely reactive

  • Nobel gases extremely unreactive, but Xe, Kr, Rn will react reluctantly with F


  • Do not fit the standard definition of metals or nonmetals

  • Include: Boron, Silicon, Antimony, Germanium, Arsenic, Tellurium

  • Located on the “staircase” of the periodic table

Metals and nonmetals
Metals and Nonmetals

Transition Metals




Atomic notation
Atomic Notation

  • Atomic number: The number of protons in the nucleus of an element (smaller number)

  • Mass number: The average atomic mass of an element (larger number)

Atomic symbols
Atomic Symbols

  • Show the mass number and atomic number

  • Give the symbol of the element

    mass number

    23 Nasodium-23

    atomic number11

More atomic symbols
More Atomic Symbols

16 31 65

O P Zn

8 15 30

__p+ __p+ __p+

__n __ n __n

__e- __e- ___ e-

Energy of electrons
Energy of Electrons

  • Electrons in atoms are arranged in levels.

  • An electron absorbs energy to “jump” to a higher energy level.

  • When an electron falls to a lower energy level, energy is released.

Energy levels are like using a stick shift in a car. The faster you travel the higher gear you use.

The bohr model
The Bohr Model

  • First model made to illustrate electron structure

  • Provides levels where an electron would most likely to be found

A Bohr model of Nitrogen.

Electron levels shells
Electron Levels (Shells)

  • Contain electrons that are similar in energy and distance from nucleus

  • Low energy electrons are closest to the nucleus

  • Higher energy electrons are farther away from the nucleus

  • The first shell (1) is lowest in energy, 2nd level next and so on 1<2<3<4

  • Many shells also have sublevels

Number of electrons per shell
Number of Electrons per shell

  • Use the formula 2n2, where n is equal to the energy level

    n =1 2(1)2 = 2

    n =2 2(2)2 = 8

    n =3 2(3)2 = 18

Periodic law
Periodic Law

All the elements in a group have the same electron configuration in their outermost shells

Example: Group 2

Be 2, 2

Mg 2, 8, 2

Ca 2, 2, 8, 2

Bohr and lewis review

Bohr and Lewis Review

Valence Electrons:

Electrons with the greatest energy

Electrons that will react to form compounds

Draw the Bohr Diagram for Al

Draw the Lewis Diagram for O

Draw the Lewis Diagram for the compound formed between Al and O. Name it.


  • 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 37Cl


    chlorine 35 chlorine 37


  • An isotope of an element that is capable of spontaneously emitting radiation in the form of particles and/or gamma rays

  • Occur naturally or can be produced artificially

  • Ex: Tritium 31H

  • Half Life: The time it takes for one 1/2 the nuclei in a radioactive sample to decay

  • Uses: Nuclear power, cancer treatment carbon -14 dating

Masses of atoms
Masses of Atoms

  • A measuring unit designed for atoms gives their atomic masses in atomic mass units (u)

  • An atom of 12C was assigned an exact mass of 12.00 u

  • The relative masses of all other atoms was determined by comparing each to the mass of 12C

  • An atom twice as heavy as 12C has a mass of 24.00 u. An atom half as heavy is 6.00 u.

Atomic mass
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

Calculating atomic mass
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
Atomic Mass of Magnesium

Isotopes Mass of Isotope Abundance

24Mg = 24.0 u 78.70%

25Mg = 25.0 u 10.13%

26Mg = 26.0 u 11.17%

Atomic mass (average mass) Mg = 24.3 u



Learning check
Learning Check!

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 u) atoms and 39.8% of gallium-71 (70.9 u) atoms. What is the atomic mass of gallium?

Finding an isotopic mass
Finding An Isotopic Mass

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