Semester 1 IB Chemistry year 11

Isotopes

Atoms of the same element with different numbers of neutrons

Relative isotopic mass

The mass of an atom of an isotope compared to 1/12th of the mass of a carbon-12 atom

Relative atomic mass, Ar

The weighted mean mass of an atom of an element compared to 1/12th of the mass of a carbon-12 atom

Relative molecular mass, Mr

The weighted mean mass of a molecule compared to 1/12th of the mass of a carbon-12 atom

Relative formula mass

The weighted mean mass of a formula unit compared with 1/12th of the mass of a carbon-12 atom

Equation: Relative atomic mass (of an element) =

[Relative isotopic mass(es) x Relative isotopic abundance(s)] / 100

Amount of substance

The quantity whose unit is the mole

Avogadro constant, Na

The number of atoms per mole of the carbon-12 isotope (6.02 x 10^23 mol^-1)

Mole

The amount of a substance containing as many particles as there are carbon atoms in 12g of carbon-12

Molar mass, Mr

The mass per mole of a substance (gmol^-1)

Equation linking molar mass, mass and number of moles:

Mr = m/n

Mr = Molar mass (gmol^-1)

m = Mass (g)

n = Number of moles (mol)

Empirical formula

The simplest whole number ratio of atoms of each element present in a compound

Molecule

A small group of atoms held together by covalent bonds

Molecular formula

The actual number of atoms of each element in a molecule

Molar volume

The volume per mole of a gas (dm^3mol^-1) (At room temperature and pressure, the molar gas volume is approximately 24dm^3mol^-1

Molar gas volume equation (at standard conditions)

V = 22.7 x n

V = Molar gas volume ((dm³mol⁻¹)

n = Amount of substance (mol)

Concentration (of a solution)

The amount of solute, mol, dissolved per 1dm³ of solution

Concentration equation

c = n / V

c = Concentration (moldm⁻³)

n = Amount of substance (mol) or mass (g)

V = Volume (dm³)

Standard solution

A solution of a known concentration

Species

Any type of particle that takes part in a chemical reaction

Acid

A species that is a proton donor

Base

A species that is a proton acceptor

Alkali

A type of base that dissolves in water forming hydroxide ions (OH-)

Cation

A positively charged ion

Anion

A negatively charged ion

Acid + Carbonate →

Salt + Carbon dioxide + Water

Acid + metal →

Salt + hydrogen

Acid + metal hydroxide →

Salt + Water

Hydrated

A crystalline compound containing water molecules

Anhydrous

A substance that contains no water molecules

Waters of crystallisation

Water molecules that form an essential part of the crystalline structure of a compound

Oxidation number

A measure of the number of electrons that an atoms uses to bond with atoms of another element

Oxidation

A loss of electrons or an increase in oxidation number

Reduction

A gain of electrons or a decrease in oxidation number

Redox reaction

A reaction in which both reduction and oxidation take place

What does O I L R I G stand for?

Oxidation

Is

Loss

Reduction

Is

Gain

Reducing agent

A reagent that reduces (adds electrons to) another species

Oxidising agent

A reagent that oxidises (takes electrons from) another species

Stoichiometry

The molar relationship between the relative quantities of substances taking part in a reaction

First ionisation energy

The energy required to remove one electrons from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ atoms

Electron shielding

The repulsion between electrons in different inner shells (Shielding reduces the net attractive force from the positive nucleus on the outer-shell electrons)

Successive ionisation energies

A measure of the energy required to remove each electron in turn

Second ionisation energy

The energy required to remove one electron from each ion in one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

Shell

A group of atomic orbitals with the same principal quantum number, n

Principal quantum number, n

A number representing the relative overall energy of each orbital, which increases with distance from the nucleus

Atomic orbital

A region within an atom that can hold up to two electrons with opposite spins

Sub-shell

A group of the same type of atomic orbitals (s, p, d or f) within a shell

Electron configuration

The arrangement of electrons in an atom

Compound

A substance formed from two or more chemically bonded elements in a fixed ratio

Ionic bond

The electrostatic attraction between oppositely charged ions

Giant ionic lattice

A three-dimensional structure of oppositely charged ions, held together by strong ionic bonds

Group

A vertical column in the periodic table (Elements in the same group have similar chemical properties and their atoms have the same number of outer-shell electrons

Covalent bond

A bonded formed by a shared pair of electrons

Lone pair

An outer-shell pair of electrons that are not involved in chemical bonding

Dative covalent (coordinate bonding)

A shared pair of electrons which has been provided by one of the bonding atoms only

Electronegativity

The ability of an atom to attract electrons in a covalent bond

Permanent dipole

A small difference across a bond that results from a difference in the electronegativities of the bonded atoms (A polar covalent bond has a permanent dipole)

Intermolecular force

An attractive force between neighbouring molecules

Permanent dipole-dipole force

A weak attractive force between permanent dipoles of neighbouring polar molecules

Hydrogen bond

A strong dipole-dipole an electron deficient hydrogen atom on one molecule and a lone pair of electrons on a different molecule

London forces (dispersion forces)

the weak attractive forces between molecules resulting from the small, instantaneous dipoles that occur because of the varying positions of the electrons during their motion about nuclei

Metallic bonding

The electrostatic attraction between positive metal ions and delocalised electrons

Delocalised electrons

Electrons shared between more than two atoms

Giant metallic lattice

A three-dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds

Simple molecular lattice

A three-dimensional structure of molecules, bonded together by weak intermolecular forces

Giant covalent lattice

A three-dimensional structure of atoms, bonded together by strong covalent bonds

Period

A horizontal row of elements in the periodic table (Elements show trended in properties across a period_

Periodicity

A regular periodic variation of properties of elements with atoms number and position in the periodic table

Thermal decomposition

The breaking up of a chemical substance with heat into at least two chemical substances

Displacement reaction

A reaction in which a more reactive element displaces a less reactive element from an aqueous solution of the latter's ion

Precipitation reaction

The formation of a solid from a solution during a chemical reaction (Precipitates are often formed when two aqueous solutions are mixed together)

Describe the line emission spectrum of hydrogen.

A series of dark lines of light of an exact frequency on a black background. The lines get closer together (converge) as frequency increases.

How are emission spectra produced?

Photons are emitted from atoms as excited electrons return to a lower energy level.

What is the shape of an s orbital?

spherical

What is the shape of a p orbital?

dumbbell shaped

In an emission spectrum what does the limit of convergence at higher frequency correspond to?

first ionisation energy

describe a continuous spectrum

Radiation spread over all wavelengths/frequencies

describe a line spectrum

radiation emitted (or absorbed) at specific wavelengths/frequencies

What is the Aufbau principle?

electrons occupy the orbitals of lowest energy first

What is Hund's rule?

Electrons will fill an unoccupied orbital before they pair up.

What is the Pauli Exclusion Principle?

an atomic orbital can contain a maximum of 2 electrons with opposite spin

PV=nRT what are the units for each variable

P=Pa

V=m³

n=mol

T=K

R = 8.314 J mol⁻¹ K⁻¹

how to convert volume in cm³ to volume in m³?

volume in cm³/10⁶= volume in dm³

How to convert from C to K

Temperature in C +273 = temperature in K

homogeneous

a process involving substances in the same phase (solid, liquid, or gaseous)

heterogeneous

a process involving substances in different phases (solid, liquid, or gaseous).

Percentage yield =

(actual yield/theoretical yield) x 100

Sketch P against V for an ideal gas at constant T (and n)

Sketch V against T for an ideal gas at constant P (and n)

Sketch P against T for an ideal gas at constant V (and n)

Why gases behave as ideal gases at low temperatures

The closer the gas is to being a liquid then the less it behaves like a real gas as the particles themselves are moving slower, are more closely spaced and take up more of the 'empty' volume of the gas

what is the limiting reagent?

The reactant in a chemical reaction that limits the amount of product that can be formed. The reaction will stop when all of the limiting reactant is consumed

How does an σ bond formed?

by the direct head-on/end-to-end/axial overlap of atomic orbitals, resulting in electron density concentrated between the nuclei of the bonding atoms

How is a pi bond (π) is formed?

by the sideways overlap of atomic orbitals, resulting in electron density above and below the plane of the nuclei of the bonding atoms.

How do you calculate Formal charge

(Number of valence electrons)-½(Number of bonding electrons)-(Number of non-bonding electrons)

How do you use formal charge to detemine the most likely lewis structure?

The Lewis (electron dot) structure with the atoms having FC values closest to zero

What hydrid orbital is present in a carbon atom with 4 σ bonds

sp³

What hydrid orbital is present in a carbon atom with 3 σ bonds and 1 π bond?

sp²

What hydrid orbital is present in a carbon atom with 2 σ bonds and 2 π bond?

sp

Which bonds are present in a C≡C bond

1σ bond and 2π bonds