4.1 Atomic Theory & Bonding ATOM: smallest particle of an element, has a neutral charge. PEN = proton(s) + electron(s) + neutron(s) ELEMENT: made up of 1 type of atom (eg.oxygen O) IONS: atoms with charges (eg. oxygen is O2-) MOLECULES: groups of covalently bonded atoms (eg. oxygen molecules are O2) COMPOUNDS: are made up of at least 2 atoms bonded together.  Hydrogen and oxygen are atoms/elements  H2O is a compound

Numbers to Remember : Protons = Atomic Number Neutrons = Mass number – Atomic number (Mass # - proton #). Electrons in an atom = atomic number (also proton #) Electrons in an ion = atomic number – ion charge

Structure of an Atom:

Name

Symbol

Charg e

Location

Atomic Mass

Proton

p

1+

nucleus

1 AMU

Neutron

n

0

nucleus

1 AMU

Electron

e

1–

area surrounding the nucleus

1/1836 (0)

Families of the Periodic Table:  Columns of elements are called groups, or families  All elements in a family have…  similar properties  bond with other elements in similar ways  have the same number of valence electrons  Family names (on the periodic table!):  Group 1 = alkali metals (1+, highly reactive)  Group 2 = alkaline earth metals (2+, reactive)  Group 17 = the halogens (1-, very reactive)  Group 18 = noble gases (0, unreactive)  Periods are horizontal rows on the periodic table.

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Periodic Table of the Elements

Periodic Table & Ion Formation: Where are the following?

INCREASING REACTIVITY

• Atomic Number • Period • Group/Family • Metals • Non-metals • Transition metals • Metalloids • Alkali metals • Alkaline earth metals • Halogens

 Ions: Atoms that gain and lose electrons to become stable (full valence shells).  1. Cations: metals that lose electrons & form positive ions (Na+)  Multivalent: Some metals can have more than one charge (Fe2+ or Fe3+).  2. Anions: Non-metals gain electrons & form negative ions (O-2)

• Noble gases

Bohr Diagrams:

Bohr Diagrams

 Bohr diagrams show how many electrons appear in each electron shell around an atom. (2, 8, 8, 18, 18)  Valence electrons: electrons in the outermost shell ONLY.  If the valence shell is full = stable  If the valence shell is not full = reactive

What element is this? •It has 2 + 8 + 8 = 18 electrons, and therefore 18 protons

18 p 22 n

•It has 8 electrons in the outer (valence) shell Argon!

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Covalent Bonds:

Ionic Bonds:  Formed between cations (metal or NH4+) & anions (non-metal or polyatomic ions).  Valence electrons are transferred to create the cation and anion.  Eg. Li2O

 Formed between two or more non-metals  Valence electrons are shared between atoms (so NO CHARGES are formed)  Eg. HF

+

Lithium

+

Oxygen

Electrons are transferred from the cations to the anion

Li+

O2Li+ Lithium oxide, Li2O

Lewis Diagrams:

Lewis Diagrams for Ions:

Ex. Nitrogen ion

 Remove or add electron dots to make full valence shells.  Square brackets and the charge are placed around each ion

 Dots representing valence electrons are placed around the element symbols (on 4 sides, imagine a box around the symbol)

Ex: Nitrogen atom

Electrons are shared

Fluorine

Hydrogen

 Only valence electrons are shown

 Electron dots are placed singularly, then they are paired.

Hydrogen fluoride

•• • • • ••

Be

••

•• • •

Cl

• •

••

Each beryllium has two electrons to transfer away, and each chlorine wants one more electron

• •

Cl ••

••

•• • •

•

• Be • • ••

• •

Cl

• •

• •

Since Be2+ wants to donate 2 electrons and each Cl– wants to accept only one, two Cl– ions are necessary

• •

•• – • • ••

Cl

2+ •• • • • • ••

Be

• •

–

•• •

Cl • ••

The ionic compound Beryllium chloride is formed

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Lewis Diagrams For Covalent Compounds:

Lewis Diagrams for Ionic Compounds:

•• • • • ••

Be

••

•• • •

Cl

• •

••

Each beryllium has two electrons to transfer away, and each chlorine wants one more electron

• •

Cl ••

•

Be • • ••

•• –

••

•• • •

•

• •

Cl

• •

• •

Since Be2+ wants to donate 2 electrons and each Cl– wants to accept only one, two Cl– ions are necessary

• •

Cl •• ••

2+ •• • • • • ••

Be

• •

–

••

Cl

• •

••

The ionic compound Beryllium chloride is formed

4.2 – Ionic and Covalent Compound Naming Ionic Compounds: - are made up of positive and negative ions arranged in a crystal structure. Salt, NaCl

Covalent Molecules: - are made up of atoms sharing electrons.

 valence electrons are drawn to show sharing of electrons.  Remember: All atoms “like” to have a full valence shell  The shared pairs (“bonding pairs”) of electrons are usually drawn as a straight line  “lone pairs” are the electrons not shared

Naming Ionic Compounds:  name of an ionic compound = cation anion-ide  Ex.1: magnesium and oxygen  cation anion-ide  Magnesium ox + ide  Magnesium oxide Magnesium  Ex.2: what is the name of Ca3N2? oxide is used as a drying agent.  Ca = calcium; N = nitrogen  Drop the end of the anion and add –ide  Calcium nitride

 Ex.3: What is the name of BaCl2?  Barium chloride

Water, H2O

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Writing formulas for Ionic Compounds Remember: positive charges must = negative charges Ex.1: What is the formula for magnesium phosphide?  Magnesium is Mg2+ Phosphorous is P3–  Lowest common multiple of 2 and 3 is 6  3 Mg2+ ions & 2 P3– ions (6 +ve’s & 6 –ve’s)  Magnesium phosphide = Mg3P2 Ex.2: What is the formula for calcium oxide? Calcium is Ca2+ Oxygen is O2– 2+ 1 Ca ion & 1 O2– ion Calcium oxide = CaO

Ionic Compound with a Multivalent Metal  Multivalent: some transition metals have more than one charge.  Roman numerals are used after the metal name to indicate which ion was used Ex. 1 What is the formula manganese(III) sulphide?  This manganese is Mn3+ Sulphur is S2–  Lowest common multiple of 3 and 2 is 6  2 Mn3+ ions and 3 S2– ions  Mn2S3

Drawing Formula Diagrams  Examples:  Lithium nitride

 Barium sulphide

You try! What is the name for TiF4?  Titanium can be Ti4+ or Ti3+ Fluorine is F–  From the ratio in the formula you can find out it is Ti4+  1 Ti4+ ion and 4 F– ions  Titanium (IV) fluoride

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Polyatomic Ions  are made up of several atoms joined together by covalent bonds  The whole group has a + or – charge, not individual atoms.  Ex.1 What is the formula of sodium sulphate?

Ex.2: What is the name of the compound KClO? ClO– = hypochlorite K+ = potassium Potassium hypochlorite Ex.3: What is the formula for Calcium nitrate? and NO3Ca2+ Ca(NO3)2

Na+ and SO42– Na2SO4

Naming Simple Covalent Compounds  Prefixes are used before the atom name to indicate the number of atoms in the molecule.

* Note the brackets around NO3 show there are two of the nitrate ions present

Examples:

 Examples: CO = carbon monoxide CO2 = carbon dioxide

 What is the name of the molecule Si3P6?  Trisilicon hexaphosphide

Write the most metallic atom (furthest left) first, then add -ide to the end of the second atom’s name

 What is the chemical formula for the molecule trinitrogen tetrachloride?  N3Cl4

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How do you know which type it is?  To determine whether a compound is ionic or covalent: - Examine the formula • Ionic compounds start with a metal or the ammonium ion • Covalent compounds start with a non-metal

4.3 Chemical Equations  A Chemical change means new compounds are formed.

 Law of Conservation of Mass: matter is not created or destroyed; atoms are just rearranged. mass of reactants = mass of products number of each = number of each atom in reactants atom in products If you could collect and measure all of the exhaust from this car, you would find that mass of reactants (gas + O2) = mass of products (exhaust)!



Chemical reactions can be written in different ways.  A word equation: Nitrogen monoxide + oxygen  nitrogen dioxide  A symbolic equation: State of matter 2NO(g) + O2(g)  2NO2(g)

Writing and Balancing Chemical Equations  word equation  uses the names of the chemicals

- Letters indicate the state of each compound

Coefficients - indicate the ratio of compounds in the reaction - here, there is twice as much NO and NO2 than there is O2

(aq) =aqueous/ dissolved in water (s) = solid (l) = liquid

 Example: K

+

O2



K2O

The word equation is:

Potassium metal + oxygen gas

 potassium oxide

(g) = gas

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Tips and Tricks  A skeleton equation shows only the formulas of the elements/compounds  Shows atoms, but is not balanced  K(s) + O2 (g)  K2O(s)  A balanced chemical equation shows the correct number of each atom  Balancing ensures that the number of each atom is the same on both sides of the reaction arrow  Always use the smallest whole number ratio  4K(s) + O2 (g)  2K2O(s)

 Use the chemical symbol to represent single elements.  Be careful of diatomic and polyatomic elements such as O2, P4 and S8  The “special seven” are all diatomic elements (hockey stick & puck)  H2, N2, O2, F2, Cl2, Br2, I2

Balancing Equations Examples Balance the following: __Sn(NO2)4 + __K3PO4  __KNO2 + __Sn3 (PO4)4

Balance the following: ___ C2H6 + ___ O2  ___ CO2 + ___ H2O

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