IB Chem SL

relative atomic mass (Ar)

weighted mean of all the naturally occurring isotopes of the element (g/mol)

relative molar mass (Mr)

sum of Ar (no units)

mole

6.02x10^-23

Empirical Formula

shows the simplest whole number ratio of atoms of each element in a particular substance

Molecular Formula

shows the actual number of atoms of each element in a particular molecule or substance

Structural formula

shows the arrangement of atoms and bonds within a molecule

stoichiometry

the fixed relationship between the reactants and products of the reaction

state symbols: (s), (l), (g), (aq)

shows the physical state of reactants and products: solid, liquid, gas, aqueous

symbol for reactions where both the reactants and the products are present in an equilibrium mixture

molar ratio

given by the coefficients, it is the ratio of the amounts of reactants and products

density

mass/volume (g/cm^3)

solute

dissolved substance

solution

a transparent, homogenous mixture; solute+solvent

concentration

amount of solute in a known volume of solvent (mol/dm^3)

ideal gas equation

PV\=nRT

n

symbol for number of moles

R

the gas constant\= 8.314 J/K mol

Electromagnetic radiation

Includes visible light, radio waves, IR, ultraviolet

Electromagnetic spectrum

Spectrum of wavelengths that comprise the various types of electromagnetic radiation.

Continuous spectrum

Spectrum that shows all wavelengths of the section of the spectrum used (eg visible or UV, or ...)

line spectrum

a spectrum showing only certain discrete wavelengths

Photon

A particle of electromagnetic radiation with no mass that carries a quantum of energy

ideal gas

an imaginary or perfect subtance whose particles are infinitely small and do not interact with each other

Avogadro's law

equal volumes of different gasses at the same temperature and pressure contain the same number of moles

Atom economy

A measure of the amount of starting materials that end up as useful products
(mass of desired product/mass of total product)*100\=%

nucleon

collective term for protons and neutrons

A

symbol for mass number

atomic number

equal to the number of protons in the nucleus (and to the number of electrons if atom (neutral))

mass number

\# of protons + \# neutrons

A-Z\=

number of neutrons

Isotopes

atoms that have the same number of protons, but different number of neutrons

Mass Spectrometer

an instrument used to measure the precise masses and relative amounts of atomic and molecular ions

isotopes used as tracers in medicine for treating and diagnosing illnesses

131 125
I & I
53 53

radioactive elements

unstable elements that decay or break down into different elements

wave equation

c\=lambda * v

c from (c\=lambda * v )

symbol for velocity of travel for light ((3*10^8 m/s)

lambda from (c\=lambda * v )

a symbol for wavelength (m)

electromagnetic radiation

a form of energy that exhibits wavelike behavior as it travels through space

sections of the electromagnetic spectrum

radio waves
microwaves
infrared radiation
visible light
ultraviolet
X-rays
gamma rays

emission spectra

consists of discrete lines that converge towards the high energy end. Characteristic to each element

s-block elements

alkali metals and alkaline earth metals

p-block

groups 13-18 on the periodic table

d-block

*area of periodic table with transition metals*

Aufbau principle

lowest energy orbitals are filled with electrons first

Hund's rule

orbitals within the same sub shell are filled singly first

First ionization energy

the energy required to remove the first electron from a mole of an atom in its gaseous state

Group 1

alkali metals

Group 7

Halogens

Periodicity

A regular periodic variation of properties of elements with atomic number and position in the Periodic Table.

atomic radius

usually defined as half the distance between the nuclei of two bonded atoms of the same element

Trend in Atomic radii

-Increases down a group
-decreases across a period

Trend in first ionization energy

-decrease down the group
-increase across period

3 most electronegative elements

F, N, and O

electron affinity

the energy change when a mole of electrons is added to a mole of atoms in a gaseous state

ionic bond

A strong attractive force resulting from the attraction between oppositely charged ions in a lattice.

properties of ionic compounds

crystalline, high melting point, electrically conductive when melted or dissolved in water

single covalent bond

one pair of electrons are shared in bond

Lewis Dot Structure

Element symbols with all valence electrons shown (ex.

Coordinate bonds

when one atom supplies both the shared electrons to form covalent bond

Bond polarity

when electrons are shared unequally, the more electronegative atom has partial negative charge, noted:

Valence Shell Repulsion theory (VSEPR)

electrons arranged around the central atoms so they are as far apart as possible

Non-bonded pairs of electrons (when compared to bonded pairs)

are more repulsive

shape of 2 electron domains

linear

shape of 3 electron domains

trigonal planar

shape of 4 electron domains

tetrahedral

bond angle of a linear molecule

180

bond angle in a trigonal planar molecule

120

bond angle in a tetrahedral molecule

109.5

resonance structure

a structure that occurs when it is possible to draw two or more valid electron (Lewis) dot structures that have the same number of electron pairs for a molecule or ion

allotropes

different forms of an element ex. diamond, graphite and fullerene

molecular polarity

overall dipole of the molecule (polar bonds do not automatically indicate dipole)

London dispersion forces

temporary instantaneous dipole (b/c unevenly spread electrons since moving), weakest attraction; shown in non polar molecules.

Dipole-Dipole forces

relatively weak attractions between polar molecules ; a form of intermolecular forces

intramolecular forces

forces INSIDE of a molecule

intermolecular forces

forces BETWEEN neighboring molecules

van der Waals forces

inclusive term for London dispersion, dipole induced dipole, and dipole-dipole IMFs

Hydrogen bonding

when hydrogen is bonded to a small highly electronegative element, e- pair is pulled away to electronegative element so it is basically just a proton, then is attracted to non bonding pair of e- on another molecule, resulting in a strong dipole-dipole IMF between molecules

relative strength of intermolecular forces

hydrogen bonding\>dipole-dipole

Metals

are elements that have delocalized electrons and typically form cations

in molten aqueous ionic compound conducting electricity

the charge is carries by the ions

metallic bond

the attraction between neighboring positive ions with delocalized electrons between and around them

malleable

can be bent and reshaped under pressure

ductile

can be drawn out into a wire

alloy

metallic solid solution (usually made up of more than one metal)

energy

the ability to do work

unit for energy

Joules (N m)

endothermic reaction

bonds in reactants are stronger than bonds in products, so energy is absorbed by the reaction

exothermic reaction

bonds in products are stronger than bonds in reactants, so energy is released by the reaction

Standard Enthalpy Change of Formation

Enthalpy change when one mole of a substance is formed from its elements

temperature

average kinetic energy of the substance

enthalpy diagram

calculation of enthalpy change in calorimetry experiment

Heat energy\=mass (m) x specific heat capacity (c) x temperature change (delta T)

specific heat capacity of water

4.18 kJ / kg K

standard conditions

100 kPa, 298 K

define specific heat capacity

energy (in J) required to heat one g of substance by one Kelvin

in enthalpy calculations assume

assume solutions have same density and specific heat capacity as water

enthalpy of combustion unit

kJ/mol

Hess' Law

enthalpy change for a reaction depends only on the difference between the enthalpy of the products and the enthalpy of the reactants (and is independent of reaction pathway)

standard enthalpy change of formation

enthalpy change when one mole of compound is formed from elements in their standard states

standard enthalpy change of combustion

enthalpy change change when one mole of a substance is completely combusted in oxygen under standard conditions