MODULE 4: MATTER AND MATERIALS

The Atom

Structure of the AtomThe Atom

++

++

-

-

-- ElectronsNucleus

Neutrons

ProtonsEnergy levels

Protons and neutrons together are called NUCLEONS

Structure of AtomSubatomic particles

particle Symbol Mass(kg)

Charge(C)

Relative Charge

Proton

Neutron

Electron

p+

n0

e-

1,67 x 10-27

1,67 x 10-27

9,11 x 10-31

+1,6 x 10-19

-1,6 x 10-19

0

+1

0

-1

Structure of the Atom - Notation

XA

Z

Mass Number• On Periodic Table

(big number)• Number of Protons +

Neutrons

Atom Number• On Periodic Table

(small number)• Number Protons

Symbol of Element

Structure of AtomIons

Atoms that gain or lost electrons to obtain an electrical charge

Negative Charge: gained electrons Positive Charge: lost electrons Number: relates the number of

electrons gained or lost.

𝑂2−816 Charge

Structure of AtomSubatomic Particles

Protons:p+ = Atom number

Neutrons: n0 = Mass number – Atom numbber

Electrons:e- = Atom number - Charge

Structure of AtomIsotopes

• Atoms with the same number of protons but a different number of neutrons

• Atoms with the same atomic number, but different mass numbers

𝐶612 𝐶6

14

n0 = 12 – 6= 6 neutrons

n0 = 14 – 6= 8 neutrons

Structure of AtomRelative Atomic Mass

• Weighted Average: Takes into account the percentage abundance of isotope

….

Where = Relative Atomic Mass (on PT)= Mass number of isotope

% Abundance = Percentage of element naturally occuring as isotope

Electron ConfigurationOrbitals

A region in space where one is most likely to find an electron

Every energy level has one s-orbital

Each energy level from the second one upwards has three p-orbitals

Electron ConfigurationOrbitals

A region in space where one is most likely to find an electron

Electron ConfigurationOrbitals

Electron OccupationOrbitals: Aufbau Pricipal

Pauli-exclusion principal:An orbital can house a maximum of two electrons if they spin in opposite directions

Orbitals with lowest energies are occupied first1s→ 2s → 2p → 3s → 3p → 4s → 3d → 4p

Hund’s rule: When there are more than one orbital of the same kind available, each orbital will first be occupied by a single electron before pairing

Electron ConfigurationValency and Valence electrons

Valence electrons:• Electrons in the outermost energy level• Number of valence electrons = group

number Noble gas structure

Completely filled outer energy level Valence• Number of electrons that an atom has to

loose or gain to obtain noble gas structure• Group 1 – 4 : Valence = Group number• Group 5 – 7: Valence = 8 – Group number

Ions All atoms tend toward noble gas structure

• Wants a completely filled valence shell Groups 1 – 3:

• Loose valence electrons• Forms positive ions• Charge = + valency

Groups 5 – 7:• Gains Electrons• Forms negative ions• Charge = - valency

Electron Configuration

𝟑𝒑𝟔Principal Energy level (n)

Type of orbital

Number of electrons in orbital

Electron Configuration