4.1:  Atomic Theory
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4.1: Atomic Theory & BONDING. 4.1: Learning Outcomes. 1. Demonstrate knowledge of the three subatomic particles, their properties, and their location within the atom.

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4.1: Atomic Theory & BONDING

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4 1 atomic theory bonding

4.1: Atomic Theory

& BONDING


4 1 atomic theory bonding

4.1: Learning Outcomes

  • 1. Demonstrate knowledge of the three subatomic particles, their properties, and their location within the atom.

  • 2. Define and give examples of ionic bonding (e.g., metal and non‐metal) and covalent bonding (e.g., two non‐metals, diatomic elements).

  • 3. With reference to elements 1 to 20 on the periodic table, draw and interpret Bohr models, including protons, neutrons, and electrons, of:

  • atoms (neutral)

  • ions (charged)

  • molecules ‐ covalent bonding (e.g., O2, CH4)

  • ionic compounds (e.g., CaCl2)


4 1 atomic theory bonding

4.1: Learning Outcomes

4. Identify valence electrons using the periodic table.

5. Distinguish between paired and unpaired electrons for a single atom.

6. Draw and interpret Lewis diagrams showing single bonds for simple ionic compounds and covalent molecules (e.g., NaCl, MgO, BaBr2, H2O, CH4, NH3).

7. Distinguish between lone pairs and bonding pairs of electrons in molecules.


4 1 atomic theory bonding

4.1: VOCABULARY

Alkali earth metals

Alkali metals

Anions

Atomic #

Atomic number

Atomic Theory

Atoms

Bohr diagram

Cations

Chemical Change

Chemical reaction

Compound

Covalent bonding

Covalent Compound

Electrons

Element

Family/Group

Halogens

Ionic bonding

Ionic compounds

Ions

Lewis Diagram

Matter

Metal

Metalloids

Mixture

Molecule

Neutron

Noble gases

Non-Metal

Nucleus

Period

Proton

Pure Substance

Stable outer shell

Subatomic particle

Transition metals

Valence electrons


4 1 atomic theory bonding

Chemistry is the study of...

MATTER!!!


4 1 atomic theory bonding

What is matter?

Anything with mass and volume!

Found in 3 phases: liquid, solid, gas

Can't be created or destroyed, it only changes form


4 1 atomic theory bonding

MATTER

Mixtures

Pure Substances

Compounds

Solutions

Elements

Mechanical

Suspensions


4 1 atomic theory bonding

CHANGES IN MATTER

PHYSICAL

CHANGE

CHEMICAL

CHANGE

No new substances produced

New substances produced

Very hard to reverse

Only a change in state or appearance

= CHEMICAL REACTION


4 1 atomic theory bonding

PHYSICAL

CHANGE


4 1 atomic theory bonding

CHEMICAL

CHANGE


4 1 atomic theory bonding

ATOMS

  • An atom is the smallest particle of an element that still has the properties of that element

  • 50 million atoms, lined up end to end = 1 cm

  • An atom = proton(s) + neutron(s) + electron(s)

See pages 168 - 169

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

ATOMS FORM COMPOUNDS

  • Atoms join together to form compounds.

    • A compound is a pure substance that is composed of two or more atoms combined in a specific way.

    • Oxygen and hydrogen are atoms/elements; H2O is a compound.

See pages 168 - 169

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

ATOMS FORM COMPOUNDS


4 1 atomic theory bonding

CHEMICAL CHANGE

A chemical change occurs when the arrangement of atoms in compounds changes to form new compounds.

See pages 168 - 169

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

CHEMICAL CHANGE

Sodium Na (solid)

Chlorine

Cl (gas)

Salt

NaCl


4 1 atomic theory bonding

ATOMIC THEORY

  • Atoms are made up of smaller particles called subatomic particles.

See page 170

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

ATOMIC THEORY

If the proton & neutron were enlarged, and each had the mass of a hippopotamus, the electron, enlarged to the same scale, would have less mass than an owl.


4 1 atomic theory bonding

ATOMIC THEORY

  • The nucleus is at the centre of an atom.

    • The nucleus is composed of -positive protons

      -neutral neutrons

    • Electrons exist in the space surrounding the nucleus.

See page 170

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

ATOMIC THEORY

  • # of protons = # of electrons in every atom

  • Nuclear charge = charge on the nucleus = # of protons

  • Nuclear charge = Atomic number

  • Atomic number = # of protons = # of electrons

See page 170

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

INCREASING REACTIVITY


The periodic table

INCREASING REACTIVITY

The Periodic Table

  • Where are the following?

  • Atomic number

See page 172

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Organization of the Periodic Table

  • In the periodic table elements are listed in order by their atomic number.

    • Metals are on the left

    • The transition metals range from group 3 -12

    • Non-metals are on the right

    • Metalloids form a “staircase” toward the right side.

See page 171

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Metals (left of zig zag line)

Physical Properties of Metals: Shiny, good conductors of heat and electricity, ductile (make wires) and malleable (thin sheets). Easily lose electrons. Like to join with non-metals. Corrode (tarnish/rust).

Nonmetals (right of zig zag line)

Physical Properties of Nonmetals: dull appearance, poor conductor, brittle (breaks easily), not ductile or malleable. Easily gain electrons. Like to join with metals, but will bond to other non-metals.

Metalloids (on both sides of zigzag line)

Physical Properties of Metalloids: have properties of both metals and nonmetals. Solid, shiny or dull, ductile and malleable, conduct heat and electricity, but not very well.


The periodic table1

INCREASING REACTIVITY

The Periodic Table

  • Where are the following?

  • Metals

  • Non-metals

  • Transition metals

  • Metalloids

See page 172

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Organization of the Periodic Table

  • Rows of elements (across) are called periods.

    • All elements in a period have their electrons in the same general area around their nucleus.

    • Example: period 3 all have 3 electron shells

sodium

magnesium

aluminum

See page 171

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Organization of the Periodic Table

  • Columns of elements are called groups, or families.

    • All elements in a family have similar properties and bond with other elements in similar ways.

    • Group 1 = alkali metals

    • Group 2 = alkaline earth metals

    • Group 17 = the halogens

    • Group 18 = noble gases

18

1

2

17

See page 171

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Organization of the Periodic Table

Group 1 = alkali metals

very reactive metals

want to give away 1 electron

ie: lithium, sodium, potassium...

18

1

2

17

See page 171

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Organization of the Periodic Table

Group 2 = alkali earth metals

somewhat reactive metals

want to give away 2 electrons

ie: beryllium, magnesium, calcium...

18

1

2

17

See page 171

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Organization of the Periodic Table

Group 17 = halogens

very reactive non-metals

want to accept 1 electron

react with alkali metals

ie: fluorine, chlorine, bromine......

18

1

2

17

See page 171

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Organization of the Periodic Table

Group 18 = noble gases

STABLE. Very non reactive gaseous non-metals

ie: helium, neon, argon......

18

1

2

17

See page 171

(c) McGraw Hill Ryerson 2007


The periodic table2

INCREASING REACTIVITY

The Periodic Table

  • Where are the following?

  • Period

  • Group/Family

  • Alkali metals

  • Alkaline earth metals

  • Halogens

  • Noble gases

See page 172

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Periodic Table & Ion Formation

  • Atoms gain and lose electrons to form bonds.

    • The atoms become electrically charged particles called ions.

See page 173

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Periodic Table & Ion Formation

  • Atoms gain and lose electrons to form bonds.

    • Metals lose negative electrons & become positive ions.

    • Positive ions are called CATIONS.

See page 173

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Periodic Table & Ion Formation

Some metals are MULTIVALENT and can lose a varying number of electrons.

For example, iron, Fe, loses either two (Fe2+) or three (Fe3+) electrons

See page 173

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Periodic Table & Ion Formation

  • Atoms gain and lose electrons to form bonds.

    • Non-metals gain electrons and become negative ions

    • Negative ions are called ANIONS

See page 173

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Periodic Table & Ion Formation

Atoms gain and lose electrons in an attempt to be STABLE.

The noble gases are stable because they have FULL outer shells of electrons. They don’t need to lose or gain any e-s.

Atoms in each period want to have the same number of electrons in their outer shell (VALENCE ELECTRONS) as the noble gases on the end of their period.

See page 173

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

BOHR MODELS

  • Bohr diagrams show how many electrons appear in each electron shell around an atom.

    • The first electron shell holds 2 electrons

    • The second electron shell holds 8 electrons

    • The third electron shell holds 8 electrons

    • The fourth electron shell holds 18 electrons

  • The noble gas elements have full electron shells and are very stable.

See page 174

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Patterns of Electron Arrangement in Periods & Groups

  • Electrons appear in shells in a very predictable manner.

    • The period number = the number of shells in the atom.

    • Except for the transition elements (family 3-12), the last digit of the group number = the number of electrons in the valence shell.

See page 175

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

BOHR MODELS

18 p

22 n

What element is this?

argon

  • It has 2 + 8 + 8 = 18 electrons, and therefore, 18 protons.

  • It has three electron shells, so it is in period 3.

  • It has eight electrons in the outer (valence) shell.

See page 174

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Forming Compounds

  • When two atoms get close together, their valence electrons interact.

    • If the valence electrons can combine to form a low-energy bond, a compound is formed.

    • Each atom in the compound attempts to have a ‘full’ outer shell of valence electrons.

See pages 176 - 177

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Forming Compounds

There are 2 types of compounds:

  • IONIC COMPOUND: metals lose electrons and non-metals gain electrons.

  • Ionic bonds form when electrons are transferred from positive (+) ions to negative (-) ions.

  • The negative and positive ions are ATTRACTED to each other and form a BOND.

See pages 176 - 177

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Forming Compounds

  • Example ionic bond:

  • lithium and oxygen form an ionic bond in the compound Li2O.

+

Electrons are transferred from the positive ions to negative ions

Li+ O2- Li+

lithium oxide, Li2O

oxygen

lithium

See pages 176 - 177

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Forming Compounds

There are 2 types of compounds:

  • COVALENT COMPOUND: atoms share electrons.

  • Covalent bonds form when electrons are shared between two non-metals.

  • Electrons stay with their atom but overlap with other shells.

See pages 176 - 177

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Forming Compounds

  • Example covalent bond

  • Hydrogen and fluorine form a covalent bond in the compound hydrogen fluoride.

+

Hydrogen fluoride

electrons are shared

hydrogen

fluorine

See pages 176 - 177

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Lewis Diagrams

  • Lewis diagrams illustrate chemical bonding by showing only an atom’s valence electrons and the chemical symbol.

  • Dots representing electrons are placed around the element symbols at the points of the compass (north, east, south, and west).

See page 178

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Lewis Diagrams

  • Electron dots are placed singly until the fourth electron is reached then they are paired.

See page 178

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Lewis Diagrams


4 1 atomic theory bonding

Lewis Diagrams

To write IONS using lewis diagrams follow these steps:

Step 1: Write the lewis diagram as you normally would.

Step 2: If the element has a POSITIVE combining capacity it will give away an electron and become a POSITIVE ION (cation). Rewrite the lewis diagram to show the element symbol in square brackets (no electrons needed as it has given them away and they now have an EMPTY outer electron shell!) then add the + charge on the outside of the brackets.

Step 3: If the element has a NEGATIVE ION (anion). Rewrite the lewis diagram to show the element symbol in square brackets with extra electrons. They will now have a FULL OUTER electron shell. Then add the - charge on the outside of the brackets.


4 1 atomic theory bonding

Lewis Diagrams of Ions

  • Lewis diagrams and IONIC BONDS:

    • For positive ions, one electron dot is removed from the valence shell for each positive charge.

    • For negative ions, one electron dot is added to each valence shell for each negative charge.

    • Square brackets are placed around each ion to indicate transfer of electrons.

2+

••

• •

• •

••

••

• •

• •

••

••

• •

• •

••

••

••

• •

••

••

• •

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••

••

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••

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••

••

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••

Be

Cl

Cl

Be

Cl

Cl

Be

Cl

Each beryllium has two electrons to transfer away, and each chlorine can receive one more electron.

Since Be2+ can donate two electrons and each Cl– can accept only one, two Cl– ions are necessary.

beryllium chloride

See page 179

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Lewis Diagrams of Covalent Bonds

  • Lewis diagrams and COVALENT BONDS:

    • Like Bohr diagrams, valence electrons are drawn to show sharing of electrons.

    • The shared pairs of electrons are usually drawn as a straight line.

See page 179

(c) McGraw Hill Ryerson 2007


4 1 atomic theory bonding

Lewis Diagrams of

Diatomic Molecules

  • DIATOMIC MOLECULES, like O2 and H2, are also easy to draw as Lewis diagrams.

The elements Hydrogen, Nitrogen, Fluorine, Oxygen, Iodine, Chlorine, and Bromine are always found as diatomic molecules.

MEMORY TRICK: IHave No Bright Or Clever Friends

See page 180

(c) McGraw Hill Ryerson 2007


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