Atomic StructureAtomic Structureand Bondingand Bonding

C3.3 Atomic structure C3.3 Atomic structure and the Periodic Tableand the Periodic Table

1 Describe the structure of an atom in terms of electrons and a nucleus containing protons and neutrons.

2 Describe the build-up of electrons in ‘shells’ and understand the significance of the noble gas electronic structures and of valency electrons

C3.3 Atomic structure C3.3 Atomic structure and the Periodic Tableand the Periodic Table

3 State the relative charges and approximaterelative masses of protons, neutrons and electrons.

4 Define proton number and nucleon number.

C3.3 Atomic structure C3.3 Atomic structure and the Periodic Tableand the Periodic Table

5 Use proton number and the simple structure of atoms to explain the basis of the Periodic Table (see C9), with special reference to the elements of proton number 1 to 20.

6 Define isotopes.

ATOMIC STRUCTUREATOMIC STRUCTURE

ELECTRON – negative,

mass nearly nothingPROTON –

positive, same mass as neutron

(“1”)

NEUTRON – neutral,

same mass as proton

(“1”)

Ancient Greeks thought all matter was made of tiny particles. My experiments in 1808

proved this. I called these particles ATOMS (Greek for “can’t be cut any smaller”.

Dalton

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Mass and atomic numberMass and atomic number

Particle Relative Mass Relative Charge

Proton 1 1

Neutron 1 0

Electron 0 -1

MASS NUMBER = number of protons + number of neutrons

SYMBOL

PROTON NUMBER = number of protons (obviously)

How many protons, neutrons and electrons?

IsotopesIsotopesAn isotope is an atom with different numbers of neutrons:

Each isotope has 8 protons – this is what “makes” it oxygen.

The mass number varies. How many neutrons does each isotope have?

THE ELECTRON RULETHE ELECTRON RULE

Electrons are arranged in SHELLS

Each shell is further away from the nucleus than the previous one

Other shells can accommodate 8 or 18 electrons

Shell 1 can only accommodate 2 electrons

Shells must be filled in order

Electronic structureElectronic structureE.g. potassium:

Potassium has 19 electrons, arranged in shells…

Nucleus

1st shell has __ electrons (FULL)

2nd shell has __ electrons

3rd shell has __ electrons

4th shell has remaining __ electron

Electronic structure

= 2,8,8,1

Mendeleev

Periodic tablePeriodic table

My periodic table arranges all the elements in groups according to their properties.

Horizontal rows are called PERIODS

Vertical columns are called GROUPS

H He

Li Be B C N O F Ne

NaMg

Al Si P S Cl Ar

K Ca Fe Ni Cu Zn Br Kr

Ag I Xe

Pt Au Hg

The Periodic TableThe Periodic TableElements in the same group have similar

PROPERTIES and the same number of electrons in the outer shell.

E.g. all group 1 metals have __ electron in their outer shell

These elements have __ electrons in their outer shell

These elements have __ electrons in their outer shells

H He

Li Be B C N O F Ne

NaMg

Al Si P S Cl Ar

K Ca Fe Ni Cu Zn Br Kr

Ag I Xe

Pt Au Hg

The Periodic TableThe Periodic TableFact 2: As you move down through the periods an extra electron shell is added:

E.g. Lithium has 3 electrons. Configuration 2,1

Potassium has 19 electrons .Configuration __,__,__,__

Sodium has 11 electrons. Configuration 2,8,1

H He

Li Be B C N O F Ne

NaMg

Al Si P S Cl Ar

K Ca Fe Ni Cu Zn Br Kr

Ag I Xe

Pt Au Hg

The Periodic TableThe Periodic TableFact 3: Most of the elements are metals:

These elements are metals

This line divides metals from non-metals

These elements are non-metals

H He

Li Be B C N O F Ne

NaMg

Al Si P S Cl Ar

K Ca Fe Ni Cu Zn Br Kr

Ag I Xe

Pt

Au Hg

The Periodic TableThe Periodic TableFact 4: (Most important) Elements in the

same group have similar PROPERTIES. This is called PERIODICITY.

E.g. Group 1 metals. They all:

1) Are soft

2) Can be easily cut with a knife

3) React with cold water

3.5 Molecules and 3.5 Molecules and covalent bondscovalent bonds

3.5 Molecules and 3.5 Molecules and covalent bondscovalent bonds

1 State that non-metallic elements form non-ioniccompounds using a different type of bonding called covalent bonding.

2 Draw dot-and-cross diagrams to represent the sharing of electron pairs to form single covalent bonds in simple molecules, exemplified by (but not restricted to) H2, Cl2, H2O, CH4 and HCl.

3.5 Molecules and 3.5 Molecules and covalent bondscovalent bonds

3 Describe the differences in volatility, solubility and electrical conductivity between ionic and covalent compounds.

4 Draw dot-and-cross diagrams to represent the multiple bonding in N2, C2H4 and CO2.

Covalent bonding

+-

+ +-

-

Hydrogen has 1 electron in its outer shell. A full first shell needs 2 electrons so two hydrogen atoms SHARE their electrons…

Now both have a FULL outer shell and are more STABLE. The formula for this MOLECULE is H2.

Dot and cross diagramsDot and cross diagramsWater, H2O:

Oxygen, O2:

OH H

O O

H

H

O

O O

Step 1: Draw the atoms (only outer shells)

Step 2: Put atoms together. Check they all have a full outer shell:

Dot and cross diagramsDot and cross diagramsNitrogen, N2:

Carbon dioxide, CO2:

Ammonia NH3:

Methane CH4:

H HN

H

HH

H

H

CN N

O OC

COVALENT BONDINGCOVALENT BONDING• 2 or more atoms share electrons.

• The actual bond is a SHARED electron pair

• Normally occurs between NON-METAL atoms.

• Atoms held together very strongly but only WEAK forces between molecules…

• …so covalent substances have LOW melting and boiling points (usually liquids or gases)

3.4 Ions and ionic bonds3.4 Ions and ionic bonds

3.4 Ions and ionic bonds3.4 Ions and ionic bonds

1 Describe the formation of ions by electron loss or gain.

2 Describe the formation of ionic bonds between metals and non-metals as exemplified by elements from Groups I and VII.

3 Explain the formation of ionic bonds between metallic and non-metallic elements.

.

3.4 Ions and ionic bonds3.4 Ions and ionic bonds

4 Describe the lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions, exemplified by the sodium chloride structure.

IonsIonsAtoms are always NEUTRAL. Ions are CHARGED and form when atoms gain or lose electrons. E.g. Hydrogen:

If the electron is lost there is a positive charge left (protons and electrons no longer cancel out).

This is an ION (in this case, a positive hydrogen ion = H+)

+-

+

negatively charged electron

positively charged proton

+

Ionic bondingIonic bonding

Na

Na

+

Example: sodium and chlorine:

Sodium has 1 electron in its outer shell. Chlorine has 7. Sodium gives its outer electron to chlorine. Both now have a FULL outer shell and are STABLE.

Positively charged sodium ion = Na+

Negatively charged chloride ion = Cl-

The force of attraction between positive and negative ions is an IONIC BOND.

Cl

Cl

-

ExamplesExamples

Mg

Magnesium chloride:

MgCl2

Cl

Cl

+ Mg

2+

Cl

-

Cl

-

Calcium oxide:

CaO

OCa + Ca

2+

O

2-

IONIC BONDING• Usually a metal bonds with a non-metal.

• One atom gives electron(s) to another.

• The actual bond is the force of attraction between the positive and negative IONS.

• Ionic bonds are very STRONG .

• GIANT IONIC STRUCTURESGIANT IONIC STRUCTURES (lattices) form with very HIGH melting and boiling points (e.g. sodium chloride)

3.6 Giant structures3.6 Giant structures

3.6 Giant structures3.6 Giant structures

1 Describe the giant covalent structures of graphite and diamond.

2 Relate their structures to the use of graphite as a lubricant and of diamond in cutting.

3 Describe the structure of silicon(IV) oxide(silicon dioxide).

Giant structures (lattices)Giant structures (lattices)

Important examples coming up!

These are large, complex structures that can be formed by covalent, ionic or metallic substances…

DIAMOND giant covalent

structure with a very HIGH melting point due to STRONG bonds between carbon atoms (hard to break)

SODIUM CHLORIDE – giant ionic lattice with HIGH melting and boiling points due to STRONG forces of attraction.

Conducts electricity when MOLTEN or DISSOLVED (ions are free to move).

GRAPHITE – carbon atoms in a layered structure with free ELECTRONS between each layer enabling carbon to conduct ELECTRICITY

METALS - electrons free to move, holding atoms together and enabling metals to conduct electricity

+

+

+

+

+++

+

+- -

- -

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Giant structures (“lattices”)Giant structures (“lattices”)

+

+

+

+

+++

+

+

1. Diamond – a giant covalent structure with a very ____ melting point due to ______ bonds between carbon atoms

2. Graphite – carbon atoms arranged in a layered structure, with free _______ in between each layer enabling carbon to conduct _________

3. Sodium chloride – a giant ionic lattice with _____ melting and boiling points due to ______ forces of attraction. Can conduct electricity when _______.

4. Metals – the __________ in metals are free to move around, holding the _____ together and enabling it to conduct _________