ATOMS

• they are indivisible particles which cannot be created nor destroyed in chemical reactions

• All matter is composed of atoms

• Different chemicals have different masses and sizes. Similar chemicals have similar characteristics

• In chemical reactions, atoms can only be rearranged

MODELS OF THE ATOM

Democritus

• introduced the concept of atoms

Dalton’s model

• also known as the “billiard ball” model

• John Dalton proposed:

  1) Atoms are tiny sphere-shaped particles that can neither be created nor destroyed
  2) Atoms of an element are identical in mass and other properties

  3) Atoms can combine or rearrange during a chemical reaction

  

  
  

  Thomson’s Model

• also known as the “plum pudding” model

• In 1897, he studied the passage of an electric current through a gas chamber. He discovers the electron

• He discovers the negatively charged electron.

• 

  
  

  Rutherford’s Model

• also known as the “nuclear” or “atomic” model

• Gold Foil Experiment

  Result 1:
  Most particles passed undeflected. The atom is mostly empty space

  Result 2:
  Some particles were deflected at an angle. The particles traveled near a positive entity.

  Result 3:

  Few particles bounced back. The particles hit a positive entity head-on

• 

  
  

• Nucleus: middle, protons are concentrated near the nucleus. Around the nucleus are the electrons.

• Protons are positively charged.

  Bohr’s Model

• also known as the “planetary” or model

• The Danish scientist proposed that the electrons occupy fixed orbits around the nucleus. Each orbit corresponds to a specific amount of energy which increases as the orbit gets farther from the nucleus.

• Electron excitation-Moves from a low-energy orbit to a high-energy orbit. It absorbs energy

• Electron de-excitation-Moves from a high-energy to a low-energy orbit. It releases energy

  

  
  

  Quantum Mechanical Model

• also known as the “electron field” or “orbital” model

• They follow these principles:

  • Duality of Matter

    Louis De Broglie

    All forms of matter have dual nature. A particle and a wave.

    Uncertainty Principle

    Werner Heisenberg

    If electrons have wave properties, their momentum and exact position cannot be determined simultaneously

• 

  
  

• These were used by Austrian physicist Erwin Schrodinger

Quantum Numbers

• A set of numbers that were derived from the mathematical Solutions of Schrodinger’s equation.

Principal Quantum Number

Symbol: n

designates the main energy level. It signifies the distance of electrons from the nucleus

Values: 1, 2, 3, 4…

Angular Momentum

Symbol: l

describes the orbital shape. Values 1, 2, 3 correspond to s, p, d, f types of orbital

Values: 1, 2 , 3(n-1)

Magnetic

Symbol: m_l

describes orbital orientation in space.

-1 to +1

Spin
Symbol: ms

Electron spin direction can either be clockwise or counter-clockwise

½ or - ½

Each orbital can only hold 2 electrons
s: 1 (2 electrons)

p: 3 (6 electrons)

d: 5 (10 electrons)

f: 7 (14 electrons)

CHEMICAL BONDING

• A chemical bond is a lasting attraction between atoms or ions that enables the formation of molecules, crystals, and other structures.

Valence Electrons

• American Chemist Gilbert Newton Lewis

• used to represent the electrons in the outermost energy level/shell of an atom. These electrons are called valence electrons

LEDS or Lewis Electron dot structure

• represents the valence electrons as dots around the chemical symbol

• Gilbert Newton Lewis

How to determine the LED of an Element?

Flerovium is located in group 4A. Therefore, it has 4 electrons. It is represented as:

Group | Dots

1A | 1

2A | 2

3A | 3

4A |4

5A | 5

6A | 6

7A | 7

8A | 8

How to determine the valence configuration of an element?

Example:

Flerovium’s electron is 114

1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 5f¹⁴ 6s² 6p⁶ 6d¹⁰ 7s² 7p²

2+2+6+2+6+10+2+6+10+14+2+6+10+14+2+6+10+2+2 = 114

To find the valence configuration, you must find the highest number. The highest numbers there are 7s² 7p²

The electrons are 2 and 2 so you must add them. Therefore, the valence configuration is 4.

It has 4 valence electrons and 4 dots in the LEDS.

Chemical Bonds

• Atoms share, lose, and gain valence electrons to achieve a noble gas electron configuration with eight electrons in the outer shell. This is called an octet.

Ionic Bonding

• a metal and nonmetal atom form an ionic bond. The atoms become electrically charged particles

• The metal loses electrons and becomes a positive ion called a cation

• the nonmetal accepts the electrons and becomes a negative ion and becomes an anion. A pair of cation and anion is called a formula unit.

Covalent Bonding

• 2 nonmetal atoms can share valence electrons and form a covalent bond. Covalently bonded atoms are called molecules

• Covalent bonds can be single, double, or triple.

One pair of electrons forms a single bond, two pairs form a double, and three pairs form a triple bond.

Polar Covalent Bonds

• 2 different nonmetal atoms form a polar bond

• This creates an uneven electron distribution in the bond.

• Electronegativity 0.5-1.7

Nonpolar Covalent Bonds

• 2 identical nonmetal atoms form a nonpolar bond

• The atoms equally share the electrons

• Electron density is the probable volume of space occupied by electrons

• the charged ends make up a dipole.

• Electronegativity 0-0.4

The polarity of Molecules

• defines the polarity(or nonpolarity) of the molecule.

Electronegativity

• measure of the ability of an atom in a chemical bond to attract electrons to itself. The more electronegative an atom is, the greater its ability to attract electrons in a bond.

EN = electronegativity

(You can see the electronegativity in the periodic table)

(round up ex: 0.79 - 8)

Example of Ionic

Na-Cl

3-0.9=2.1

Therefore EN>1.8

K-I

2.5-0.8=1.7

Therefore 0.4<EN<1.8

Example of Polar

C-O

3.5-2.5=1

Therefore 0.4<EN<1.8

Example of Nonpolar

H-H

2.1-2.1=0

Therefore EN<0.4

Ionic compounds

• compounds formed during ionic bonding

Covalent compounds

• compounds formed during ionic bonding

Metallic Bonding

-it only happens between metals. It occurs when metal atoms share their pooled valence electrons.

Properties of Metallic Bonds

Lusterous - shiny

Heat conductive

Ductile - can be stretched, broken, and reformed

Malleable - compressed into thin sheets

Strong

Electrical Conductivity

London Dispersion Force

• a temporary attractive force occurs when 2 adjacent atoms form temporary dipoles as a result of the positions occupied by their electrons

Dipole-Dipole Interaction

• attractive forces between the positive end of one polar molecule and the negative end of another polar molecule

Hydrogen Bonding

• strong dipole-dipole interaction between a hydrogen atom bonded to a high electronegative atom

ORGANIC COMPOUNDS

Compounds

• 2 or more elements combined

Carbon

• all organic compounds contain carbon but not every compound contains carbon

• has the ability to join with several chemicals at the same time.

Examples of Organic Compounds

carbon

hydrogen

nitrogen

oxygen

phosphorous

sulfur

Hydrocarbons

• compounds containing carbon and hydrogen only

Aliphatic

• present in food

• Dark choco- phenethylamine

• Milk choco- butyric acid

• White choco-palmitic acid

Aromatic

• smell(ex. TNT or Trinitoluene)

• used in plastic and petrochemical industries

• present in chlorophyll

Root Words for Hydrocarbon Nomenclature

Nomenclature

• chemical nomenclature and the names that we use for chemicals

Examples:

Systematic Common

H20 Water

Single Bond -

Double Bond =

Triple Bond 3-

C5H2(5)+2 - equation

C5H12 - molecular Formula

Classification of Hydrocarbon

• Saturated Hydrocarbons

• Unsaturated Hydrocarbons

• Aromatic Hydrocarbon

Structural Formula:

These are Saturated Hydrocarbons

Saturated Hydrocarbon

• can contain only carbon-carbon single bonds

• they are saturated because they have the maximum number of bonded hydrogen

Unsaturated Hydrocarbon

• contains carbon-carbon double/triple bond

Alkenes

-contain at least one carbon-carbon double bond

Ex. Ethene

Alkynes

• contain at least one carbon-carbon triple bond

Ex. Ethylene

Aromatic Hydrocarbon

• contains at least one special type of hexagonal ring of carbon atoms with three double bond in the alternate positions.

Ex.

Toluene

• the aromatic compounds may also contain more than one benzene rings.

Ex. Naphthalene

Hydrocarbon Types

1) Saturated(Alkanes)

2) Unsaturated(Alkynes, Alkenes)

3) Aromatic

Characteristics

1) Single Bond

2) double and triple bond

3) Benzene ring

Example

1)CH3CH2CH3 - Propane

2)CH3-C-CH - Propyne

3) Methyl Benzene

Aufbao Principle

• electrons fill lower-energy atomic orbitals before filling higher-energy ones.

• was initially proposed by Niels Bohr

Alkanes

• saturated hydrocarbon containing only a carbon-carbon single bond in their molecule. They are also called Paraffins

• Undergoes reactions at high temperatures and pressure

They may be divided as:

Open Chain or acylic alkanes (CnH2n+2)

Cycloalkanes or cyclic alkanes(C2H2n)

Example of Open Chain:

C1h4 (Molecular formula)

Expanded structural formula:

Name: Methane

Nomenclature of Alkanes

• implies assigning a proper name

1. Longest chain rule

   • Select the longest continuous chain or parent chain of carbon atoms

2. Position of the substituent

   • The substituent is the branch of carbon atoms

   • For substituents, you change the bond(ex. ane, ene, etc.) into yl.

     Ex.

     Butane (remove ane)

     Butyl (replace with yl)

   • carbon atoms of the parent chain are numbered to identify the parent alkane

Ex.

3. Lowest set of locants

   • Locants refer to the position of the substituents

   • Depending on the location of the substituent, the numbering of the parent chain differs.

4. Presence of more than one substituent

   Number to number (,)

   Number to letter (-)

   

   • If the substituents are similar:

   • Number, number-prefix/substituent/parent chain

   Example:

   Number:2, 4

   Prefix: di

   Substituent: Methyl

   Parent Chain: Pentane

   The name is: 2,4-dimethylpentane

   • If the substituents are not similar:

   • Alphabetical order

   
   Number: 3, 6

   Substituents: Ethyl and methyl

   Parent Chain: Octane

   Alphabetical Order: Ethyl first before methyl

   The name is: 3-ethyl-6-methyloctane