Term 2

all the complicated words for Term 2

Define: Percipitate

A solid formed from a change in a solution, often due to a chemical reaction.

Define: Ligand

Ligands are ions or neutral molecules that bond to a central metal atom or ion. Ligands act as Lewis bases (electron pair donors), and the central atom acts as a Lewis acid (electron pair acceptor).

What is Electron Geometry? +its shapes

The arrangement of electron pairs around a central atom. Excludes lone pairs, BUT repulsion from lone pair(s) is taken into account in bond angles.

LINEAR, TRIGONAL PLANAR, TETRAHEDRAL

What is Molecular Geometry? +its shapes

The three-dimensional structure or arrangement of atoms in a molecule.

LINEAR, BENT, TRIGONAL PYRAMIDAL, TRIGONAL PLANAR, TETRAHEDRAL

Define: Polarity

The separation of the electric charge which leads to a molecule having a negatively charged end and a positively charged end.

What causes a molecule to be polar/non-polar?

1. Existence of Polar Bonds (electronegativoity)

2. The shape of the molecule (symmetrical can cancel out polarity)

3. The size of the polar portion compared to the non-polar portion.

Electronegativity

The tendency for an atom to attract electrons toward itself

Electronegativity difference (define and remember symbol)

The difference in electronegativity between two bonding atoms. It can tell us a rough measure of polarity and thus the bond type.

The ranges for covalent and ionic bonds (based on electronegativity difference)

0.0-0.4 Non-polar COVALENT

0.4-1.8 Polar COVALENT

>1.8 Ionic Bonding

What is a dipole moment?

The measure of the electrical polarity of a system of charges. Has a magnitude and direction.

In polar covalent bonds the more electronegative atom gets a partial negative charge  𝛅^- and the less electronegative gets
partial positive charge 𝛅⁺

What is a net dipole moment?

The sum of vectors. Net dipole moments must be >0 for a molecule to be polar (dipole moments are always present with vectors).

Different reactions (5)

Combustion

Redox

Neutralization

Decomposition

Replacement/ Displacement/ Persipitation

Combustion

Fuel and Oxidant (O2) combust to produce CO2 and H2O (organic compounds)

Metals combust to form metal oxides

Redox

“Electrons are transferred“

Atom that loses electrons undergoes oxidation and forms a cation

Atom that gains electrons undergoes reduction and forms a anion

Neutralization

Acid and base react to form H2O and salt

Decomposition

Compounds are broken down into smaller compounds.

Replacement/ Displacement/ Precipitation

Atom/Ion get replaced for another atom/ion

Single replacement:

CuSO₄ (aq) + Mg (s) → Cu (s) + MgSO₄ (aq) 

Double replacement:

Pb(NO₃)₂ (aq) + 2 KI (aq)  →  PbI₂ (s) + 2 KNO₃ (aq)

The Brønsted-Lowry Theory

• A Brønsted-Lowry acid is a proton (hydrogen ion) donor

Examples of acids:

• Strong acids: HCl, HNO₃, H₂SO₄, HBr, HI, HClO₄

• Weak acids: All other acids, such as HCN, HF, H₂S, HCOOH

• A Brønsted-Lowry base is a proton (hydrogen ion) acceptor

Examples of bases:

• Strong bases: The hydroxides of the Group I and Group II metals such as LiOH, NaOH, KOH etc.

• Weak bases: All other bases, such as NH₃, CH₃NH₂, C₅H₅N

Limiting reactant

Reactant which runs out first and thus determines the max amount of the product.

n (excess) = n(total) - n(used)

Types of yield:

Theoretical yield, Actual yield, Percentage yield

Titration

The slow addition of a known amount of a substance with a known concentration (titrant) to a known amount of another substance with an unknown concentration

Equivalence point

When the amount of titrant is equal to the amount of analyte according to the mole ratio in the balanced reaction equation.

Types of Titration

Acid-Base (change in pH seen by the indicator color change)

Redox (change in conductivity)

Complexometric (color change of complex formed)

Percipitation (percipitate formed)

Back

Back titration

When a sample cannot be titrated directly.

Excess acid is titrated

Green chemistry principles

• Prevent! 

• Atom economy

• Less hazardous and safer chemicals in synthesis;
  Reactants, products, by-products and solvents

• Energy efficiency

• Renewable feedstock

• Recycling of chemicals

• Analysis and real-time monitoring of pollutants

Atom economy

measure of efficiency of a reaction. Based on the singular molar mass of a chosen product against the combined molar mases of all starting materials, catalysts and solvents used in the reaction: 

VSEPR theory

Valence Shell Electron Pair Repulsion theory

Valence Shell Electron Pair Repulsion theory components

• When a molecule is formed, the outer shell electrons repel each other

  • The molecule takes the shape which minimises the repulsion between
    electron domains

  • Electron domain
    =  the region in which electrons are
    most likely to be found. Bonding pairs, lone pairs,
    single, double, and triple bond represents
    each one region of an electron domain.

immiscible

(of liquids) not forming a homogeneous mixture when mixed.

volatility

How readily a substance vaporizes.

The more non-polar, the more volatile because non-polar substances tend to have weaker intermolecular forces.

Metals

high m.p and b.p

solid at room temp

conductive (heat + electricity)

Shiny, Hard

High desnity

Ductile/Malleable

Metallic bonding

Strong electrostatic attraction between metal cations & delocalized elctrons

why are metals shiny:

Electrons absorb photons and then reflect them out. They absorb the light energy and emit them back out.

Why are metals malleable

The layers of atoms can slide over each other without breaking the metallic bond. This is because the delocalized electrons allow atoms to move freely.

Why are metals conductive

The delocalized electrons can carry a charge and also move around and conduct heat.

Charge density definition

Charge density is the measure of electric charge per unit volume or area in a given space, indicating how concentrated the charge is within that region.

What affects the charge density

The charge and radius of metal cations.

Ionic bonding

Formed between a metal and a non-metal. Strong electrostatic attraction between oppositely charged ions (+ and -).

Coordination number

The number of nearest neighboring atoms or ions surrounding a central atom in a coordination complex (AKA Lattice).

Lattice Enthalpy definition

The heat energy needed to break ionic lattice. the magnitude depends on the charges of the ions and the distance between them.

-Greater charge, greater electrostatic attraction, greater Lattice Enthalpy

-Larger radius, greater separation of charge, smaller Lattice Enthalpy

properties of Ionic molecules:

High m.p. and b.p

Solids at room temp →hard

Form crystal lattice

Dissolve in polar substances (like dissolves like)

Conducts electricity in molten or aqueous states. (electrolytes)

Low/non-volatile

Why do ionic substances condusct electrity in aqueous states?

Electrostatic attractions hold anions and cations in definite positions bin solid form while in aqueous form, ions are free to move and carry electric charges

What is a ion-dipole bond?

A type of intermolecular force that occurs between an ion and a polar molecule, where the positive or negative charge of the ion interacts with the partial charges on the polar molecule.

What is covalent bonding

The sharing of electron pair(s). It’s a strong electrostatic attraction between electrons and positively charged nuclei.

occurs in non-metals.

neutral compounds (=no charge) with covalent bonds are called molecules.

What is coordinate or diative covalent bonding

in some molecules and plyatomic ions, both electrons shared are from the same atom.

(arrow points to reciever)

properties of covalent compounds

Low m.p and b.p.

Solids, liquids, or gases at room temp

Do not conduct electricity

Dissolve in non-polar substances

What is Green chemistry?

The area of chemistry that focuses on the design of chemical products or the processes that reduce or eliminate the use or generation of hazardous substances

What is Atom economy?

Measure of the efficiency of a reaction. (M of one product compared with combined M of all starting materials, catalysts, and solvents)

Bond order

#Bonding pairs between two atoms

greater bond order=stronger bond and shorter bond length

Bond enthalpy

Amount of energy needed to break a covalent bond

Giant covalent structures

• the atoms are bonded by covalent bonds in a continuous network

• the entire crystal may be considered as a one giant macromolecule

→ atomic lattice

→ Much higher boiling points!