4.1: atomic theory & bonding

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., O‐ 2, CH4) • ionic compounds (e.g., CaCl2)

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.

Alkali earth metalsAlkali metalsAnionsAtomic #Atomic numberAtomic TheoryAtoms Bohr diagramCations Chemical ChangeChemical reactionCompound Covalent bonding

MoleculeNeutronNoble gasesNon-MetalNucleusPeriodProtonPure SubstanceStable outer shellSubatomic particleTransition metalsValence electrons

Covalent CompoundElectronsElement Family/GroupHalogensIonic bondingIonic compoundsIonsLewis DiagramMatterMetalMetalloidsMixture

MechanicalMechanicalSuspensionsSuspensions

SolutionsSolutions ElementsElements CompoundsCompounds

(c) McGraw Hill Ryerson 2007

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

See pages 168 - 169

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

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


• 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


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

See pages 168 - 169


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

See page 170

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.


• 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


– # 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

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The Periodic Table

Where are the following?• Atomic

number

See page 172

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• 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

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 Table

Where are the following?• Metals

• Non-metals

• Transition metals

• Metalloids

See page 172

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– 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

See page 171

sodium magnesium aluminum


–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

See page 171

1 2 1718


Group 1 = alkali metalsvery reactive metalswant to give away 1 electronie: lithium, sodium, potassium...

See page 171

1 2 17

18


Group 2 = alkaline earth metalssomewhat reactive metalswant to give away 2 electronsie: beryllium, magnesium, calcium...

See page 171

1 2 17

18


Group 17 = halogensvery reactive non-metalswant to accept 1 electronreact with alkali metalsie: fluorine, chlorine, bromine......

See page 171

1 2 17

18


Group 18 = noble gasesSTABLE. Very non reactive gaseous non-metalsie: helium, neon, argon......

See page 171

1 2 17

18


The Periodic Table

Where are the following?• Period

• Group/Family

•Alkali metals

• Alkaline earth metals

• Halogens

• Noble gases

See page 172

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• Atoms gain and lose electrons to form bonds.– The atoms become electrically charged

particles called ions.

See page 173


• Atoms gain and lose electrons to form bonds.– Metals lose negative electrons & become

positive ions.

– Positive ions are called CATIONS.

See page 173


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


• Atoms gain and lose electrons to form bonds.– Non-metals gain electrons and become

negative ions– Negative ions are called ANIONS

See page 173


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


• 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

See page 174

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


• 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 See page 174

What element is this?

• 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.

18 p

22 n

argon


• 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 See pages 176 - 177


• Example ionic bond:• lithium and oxygen form an ionic bond in the

compound Li2O.

See pages 176 - 177

lithium oxygen

+

Electrons are transferred from the positive ions to negative ions

Li+ O2- Li+

lithium oxide, Li2O


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


• Example covalent bond• Hydrogen and fluorine form a covalent bond in

the compound hydrogen fluoride.

See pages 176 - 177

hydrogen fluorine

+

electrons are shared

Hydrogen fluoride


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

See page 178

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


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

See page 178

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.


• 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.

See page 179

Be Cl• •

• •• •

• •

• •• •• •

• •Each beryllium has two

electrons to transfer away, and each chlorine can

receive one more electron.

BeCl Cl• •

• •• •

• •

• •• •• •

• •

• •• •• •

• •

BeCl Cl• •

• •• •

• •

• •• •• •

• •

• •• •• •

• •Since Be2+ can donate two electrons and each Cl– can

accept only one, two Cl– ions are necessary.

beryllium chloride

2+ ––


• 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 See page 180

• 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: I Have No Bright Or Clever Friends

http://en.wikipedia.org/wiki/File:Nitrogen-3D-vdW.png

4.1: atomic theory & bonding

Documents

single atom

cman atom

gold dust

bonding pairs of electrons

unpaired electrons

arrangement of atoms

bar of gold

molecules covalent bonding