Year 11 SACE Chemistry exam semester 1

Unit 3,2,1 missing hydrocarbons and subshells

What are non bonding pairs called?

Lone pairs

Electrons have a mutual force of

repulsion between electron pairs.

Why is electron repulsion important?

Because it can shape the molecule

VSPER THEORY

forms arrangements of molecules to minimize repulsion, it is at the minimum repulson when there is more distance between pairs.

This is:

Linear

This is:

bent

This is:

Trigonal planar

This is:

Trigonal pryamidal

This is:

Tetrahedral

Molecular polarity is

 permanent separation of electric charge, and the formation of delta positives and negatives

When does polarization happen?

in a covalent bond

how does polarization happen?

if there is uneven sharing of electrons.

-Electrons are attracted to the element with the highest electronegativity.

molecular polarity is determined by

the symmetry of the molecule

and the polarity of electronegativity between the atoms

intramolecular bonds

occur in the molecule (primary bonds) (eg, ionic)

intermolecular bonds

occur with the molecule and other molecules (secondary bonds

What properties are dependent on the strength of intermolecular bonds?

Melting and boiling point

What are (London) dispersion forces

dispersion forces occur when electrons that are constantly moving are unsymmetrically distributed, creating a temporary dipole

what makes stronger dispersion forces?

a bigger molecule, bigger the molecule, more interaction therefore more bonds and bigger melting points

What are dipole dipole interactions?

Occurs between a polar covalent bond,

Dipole dipole interactions are the mutual force Mutual force of attraction between the delta + of one molecule and the delta – of a second molecule.

Dipole Dipole interactions are dependant on

•Distance between molecules

•Magnitude of electric charge on both molecules

What are hydrogen bonds?

A stronger dipole dipole reaction that occurs between a delta positive of hydrogen and a delta negative of fluorine, oxygen, nitrogen

Electrical conductivity

Materials with free electrons

Heat conductivity

Materials with charged electrons for efficient heat transfer.

Homogenous mixture

Evenly distributed mix like solubles; opposite of heterogeneous.

Heterogeneous mixture

Mix with visibly different layers like oil and water.

Filtration

Separation method for solid

Evaporation

Separation method for soluble in a solvent.

Distillation

Separation method for liquids with different boiling points.

Nanomaterial

Material a billionth of a meter with unique properties.

Atomic number

Number of protons in an atom.

Atomic mass number

Sum of protons and neutrons in an atom.

Emission spectra

Light absorbed then reemitted when the electrons jump back down the levels

Absorption spectra

Light absorbed by atoms so the electrons jump energy levels.

Isotope

Atoms with same protons but different neutrons.

Average atomic mass

Weighted average of isotopes' masses.

Subshell electron configuration

Arrangement of electrons in subshells of an element.

Moles calculation

Moles = Mass of sample / Molar mass.

Avogadro's number

1 mole = 6.02 x 10^23 particles.

Molar mass calculation

Sum of (Molar mass x number of atoms) in a compound.

Periodic table period

Horizontal rows indicating number of electron shells.

Periodic table group

Vertical columns showing valence electrons.

Electronegativity trend

Increases across periods, decreases down groups.

Ionization energy trend

Increases across periods, decreases down groups.

Atomic radius trend

Decreases across periods, increases down groups.

What determines chemical properties?

valence electrons

What determines physical properties?

Protons and neutrons

What does high electronegativity mean?

the atom really want to GAIN electrons to become stable

What group has low ionisation energy?

Alkali metals

What is ionisation energy?

the minimum amount of energy required to remove 1 electron form an atom

What is atomic radius?

the distance from the nucleus to the outermost electron

How does atomic radius increase?

It increases by the size of the nucleus, and the amount of shells it has

Number of moles equals

mass/molar mass

number of atoms equals

No. Of mol x Avogadro's number.

Mass equals

Molar mass divided by moles

Electrostatic force of attraction

Attraction between two different charges in a molecule, eg : delocalized electrons and metal cations in metallic materials.

Malleable

Ability to be hammered or rolled into thin sheets.

Ductile

Ability to be drawn into wires.

Thermal Conductors

Materials that allow the flow of heat.

Electrical Conductors

Materials that allow the flow of electricity.

Melting Point (Metallic Bonds)

Increases with higher charge and larger atomic radius of metal cation.

Ionic Bonds are formed by

The transfer of electrons, resulting in cations and anions attracting each other.

Hard (Ionic Bonds)

Physical property due to strong inter-ionic forces.

Brittle (Ionic Bonds)

Easily broken or shattered.

Conductivity (Ionic Bonds)

Poor in solid state, good when dissolved or molten.

Strongest Ionic Bonds

When ions have high charges, leading to higher melting points.

Covalent Bonds

Formed by sharing electron pairs between atoms.

Electron Dot Diagrams

Illustrate electron distribution in atoms and covalent compounds.

Valence Structure

Shows all bonds and non bonded valence electrons

Polar Covalent Bonds

Result from unequal sharing of electrons, creating partial charges.

Non Polar covalent bonds

the covalent atoms have no difference in electron negativity

Electronegativity

Measure of atom's attraction for electrons.

Diatomic Molecules

Molecules composed of two atoms of the same element.

Continuous Covalent Compounds

Diamond, Graphite, Silica; have unique structures and properties.

Empirical Formula

Simplest whole number ratio of elements in a compound.

What make up metallic bonds?

Two metals

The structure of Metallic bonds

Attractive force between free moving delocalised electrons and a metal cation within a metallic material.

What are the properties of metallic bonds?

Malleable/ductile/thermal and electrical conductors due to sea of electrons within metallic bonds. .Conductive (of heat and electricity) malleable and ductile

In metallic bonds, the bigger the atomic radius

the higher the melting point

What makes up an Ionic compound

A non metal and a metal

How ionic bonds form

both the non metals and metals would like to have a full shell, so one atom gives the other its electron, and one becomes a cation and one becomes a anion

How are ionic bonds held together?

electrostatic force of attraction

what is the structure of ionic bonds

A regular lattice

Why are ionic compounds brittle?

they are brittle due to if they are pushed their lattice will move and negatives and positives will be next to eachother, and they will repell eachother

ionic compound properties

brittle(break easily when lattice move and charges overlap, high melting points (held together by eletrostatic forces)

What happens when ionic compounds are dissolved or are liquid?

they can conduct electricity

When are ionic bonds the strongest?

Ionic bonds are the strongest when each elements ionic charge are high, this makes a high melting point

What are covalent bonds made up of?

two non metals

What ionic charge does group 1 make?

1+

What ionic charge does group 2 make?

2+

What ionic charge does group 13 make?

3+

What ionic charge does group 14 make?

4+-

What ionic charge does group 15 make

-3

What ionic charge does group 16 make?

-2

what ionic charge does group 17 make?

-1

balancing is when

the total positive charge = the total negative charge

What are the 3 types of covalent bonds?

single (share one), double( shares two ), triple( shares 3)

What is a polar covalent bond?

if there is a difference in electronegativity in a covalent bond, a polar bonds.forms

what cant form polar bonds?

diatomic molecules and hydrogen+carbon (and to atoms with every low different in electronegativity

electronegativity

attractive power of electrons

What is a covalent molecular compound?

two or more nonmetal atoms sharing electrons to become more stable (covalently bonding)