Chapter 5 : Electrons and bonding

What’s the equation for the maximum number of electrons in a shell (n)?

2n²

The shells in the atom what are they regarded as?

The shells are regarded as energy levels!!

The energy increases as the shell number increases!!

In shell number 1,2,3,4 work out the number of electrons in each shell?

1 shell number = no.of.electrons 2

2 shell number = no.of.electrons 8

3 shell number = no.of.electrons 18

4 shell numer = no.of.electrons 32 Number of electrons = 2n²

What are shells made up of?

Shells are made up of atomic orbits

How many orbitals do I need to know?

1. S-orbital

2. P-orbital

Explain S-orbitals and the features of it?

• Sphere shape

• Can hold maximum 2 electrons —→ 1s²

• The greater the shell number (n) the greater the radius of it’s S-orbital!

Explain the features of P-orbitals?

• Dumb-bell shape

• Has 3 seperate p-orbitals: P_x,P_y, P_z

• Each shell has 3 P-orbitals e.g. 1s² 2s² 2p³

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In order of the shells what orbitals are you expected to see?

1st shell = 1s² [S-orbital]

2nd shell = 2s² 2p³ [ S-orbital and P-orbital]

3rd shell and 4rth shell overlap = 3s² 3p³ 3d⁵[ overlap between 4s and 3d]

4rth shell = 4s² 4p³ 4d⁵ 4f⁷

In 3rd shell how many d-orbitals and 4rth shell how many f-orbitals are used?

d-orbital : Each shell from 3rd shell contains 5 d-orbitals!!

F-orbitals : Each shell from 4th shell contains 7 f-orbitals!!

Who has a higher energy and why 2p and 2s?

2p [higher energy] > 2s

Which energy level overlaps and who needs to filled up first?

3d [higher energy] > 4s [ weaker energy]

This means 4s needs to be filled before 3d subshell

Explain the idea of the electrons-in-box model?

• Electrons are negatively charged and repel one another.

• Electrons of the arrows up and down are “spins”

• Opposite spins help to counteract the replulsion between the negative charges of the 2 electrons!!

Explain the naming of the shorthand electron configuration?

1. Look at the noble gas (Group 7) [before element!! to the left]

2. you see how many electrons that noble gas has

3. Then you mention it […] then add the extra subunits of electrons to reach the atom. E.g. [Ne]3s¹

Define Ionic Bonding?

It’s the electrostatic attraction between positive and negative ions

It holds together cations (positive ions) + anions (negative ions) in ionic compound

Workout the ionic compound structure of Potassium Fluoride?

Look at notes

Workout the ionic compound is MgCl₂?

Look at notes

Structure of Ionic Compunds?

• Giant ionic lattice structure

• - charge present next to a + charge

Describe the melting and boiling points of ionic compounds?

High melting point and boiling point

High temperatures needed to break strong electrostatic attraction between ions.

There’s not enough energy to break the electrostatic forces!!

Increase melting point for ionic lattices what else happens if it increase?

Show me an example?

Increase melting point ; Greater ionic charges!! [ stronger attraction between ions]

Ionic attraction —→ depends on the size of the ions

One element with higher charger means stronger attraction between ions.

E.g.

NaF —→ Na⁺F^-

CaF₂ —→ Ca²⁺F^-

Ionic compounds when can they conduct electricty and when can’t they?

• Ionic compounds in a solid state do not conduct electricty

• Ions are in a fixed position in the giant ionic lattice!! No mobile charges carriers

• In liquid state, the ions are mobile charge carriers

Define Covalent Bonding?

Is the strong electrostatic attraction between a sharred pair of electrons and the nuclei of the bonded atoms

What’s the difference between Covalent bonding and Ionic bonding?

Covalent Bonding —→ electrons are shared!!

Ionic bonding ————> Electrons are transfered!!

What’s the 2 different types of covalent bonds?

1. Normal Covalent Bond

2. Dative Covalent Bond

Define Normal Covalent Bond?

Each atom contributes 1 electron so 1 electron from 1 atom and another 1 electron from the atom!!

Define Dative Covalent Bond?

The arrow shows that both electrons come from one element

Dative = 1 atom donates both electrons

What does Average bond enthalpy mean?

It’s a measurement of a covalent bond strength!!

The increase average bond enthalpy ; High increase covalent bond ; High bond strength.