AP Chem Ch 1 & 2

Nonzero integers

always count as sig figs

leading zeros

zeros that precede all the nonzero digits (do not count as sig figs)

captive zeros

zero between non zero digits (always count as sig figs)

trailing zeros

zeros at the right end of the number (only significant if the numbers contain a decimal point)

exponential notation

number of sig figs can be easily indicated and fewer zeros are required to write a very large or very small number

exact numbers

-determine by counting and not by using a measuring device

-assumed to have an infinite amount of sig figs

-can arise from definitions

Sig fig rules in multiplication or division

-# of sig figs in the result is the same as the # in the least precise measurement used in the calculation

sig fig rules in addition or subtraction

result has the same # of decimal places as the least precise measurement used in calculation

Rules for rounding

-round off only after carrying the extra digits through the final result

-if the digit removed is less than 5 preceding dig it stays the same

-greater than or equal to 5- preceding digit is increased by 1

-do not round sequentially (round only in final result)

Certain digits

numbers that remain the same regardless of who measures them

uncertain digits

-digits that must be estimated and therefore vary

-while reporting a measurement, record all certain digits plus the first uncertain digit

Uncertainity

-uncertainty of a measurement depends on the precision of the measuring device

-sig figs: # in which the certain digits and the first uncertain digit are recorded

-uncertainty in the last number is always assumed to be + or - 1 unless otherwise indicated

Accuracy

agreement of a particular valur with the true value

precision

-degree of agreement among several measurements of the same quantity

-represents the reproducibility of a given type of measurement

Random Error

(intermediate error)

-measurement has an equal probability of being above or below the true value due to pure chance

-occurs in estimating the value of the last digit of a measurement

systematic error

(determinate error)

-causes bias in the result

-can skew the data

-either always be too high or too low from the true value

Quantitative work

-precision is often used as an indication of accuracy

-assumption: average of a series of precise measurements that is accurate or close to the true value

-valid if systematic errors are absent

Density

-property of matter that is used as an tag id for substances and density of a liquid can be determined by weighing an accurately known volume of liquid

-density=mass/volume

Homogenous mixture

-has visibly indistinguishable parts and is often called a solution

Heterogenous mixture

Has visibly distinguishable parts

-can be separated into pure substance, which have constant compositions, by physical methods

Distillation

-heating the mixture in a distillation device

-most volatile components (carbon based chemicals that easily turn into gas at room temp) vaporizes at the lowest temp

-vapor is passed a condenser, where is condenses back into its liquid state

-if the mixture contains several volatile components, one step distillation does not give a pure substance in the receiving flask

Filtration

-used when a mixture consists of a solid and a liquid

-mixture is poured onto a mesh, such as filter paper, which passes the liquid and leave the solid behind

Chromatography

-use a system with two state (phases of matter)

-separation occurs because the components of the mixture have different affinities for the two phases

Ionic bonds (intramolecular forces)

-Ionic bonds transfer (gain or loss) electrons between metals and non-metals

-attraction of positive and negative ions (electrostatic attractions)

-ions are atoms or molecules that has a net electrical charge (positive or negative charge) like cations (forms when an atom gains electrons)

-metals like to give away electrons, so they form positively charged ions

-while non-metals like to receive electrons, so they form negatively charged ions

-ionic bonds are result of transfer of electrons and the bonds hold them together by their electrostatic force between opposite charges

Covalent bonding (intramolecular forces)

-sharing of electrons between non-metals

-on the periodic table, the first row should have a total of 2 electrons

-the second row should have 8 electrons

Polar covalent bonds

-electrons are shared unequally

Non polar covalent bonds

-electrons are shared equally

Valence electrons of each group

Group 1/1A: 1 (H, etc…)

Group 14/4A: 4 (C, Si, etc…)

Group 15/5A: 5 (N, P, etc…)

Group 16/6A: 6 (F,Cl, Br, etc…)

Group 18/8A Noble gases: 8 (expect He)

Dipole Dipole (covalent and intermolecular)

-permanent bonding

-when you have an object where one side is positive and the other side is negative

-polarized object (unequal distribution of charge)

Intramolecular forces

bonds within a molecule, like ionic and covalent

Intermolecular forces

-forces of attraction between molecules

London dispersion (intermolecular)

-attractive forces that leads to instantaneous dipoles in the molecules

-instantaneous is a temporary-separation of positive and negative charges that causes one side to be slightly negative or positive, which pulls the electrons of a neighbor

-weakest intermolecular force and the only possible intermolecular force for non-polar

-this force increases as molar mass increases

Hydrogen bonding (intermolecular)

-occurs when hydrogen bonds directly to F, O, or N

-It acquires large particle charges that allow for strong dipole dipole attractions

-hydrogen atom is negative

-weak bond, but can become strong when they work together in large numbers

Naming Ionic compounds

-Ionic: substance made of charged ;particles called ions, such as cations and anions

Binary Ionic

Chemical substance made up of positively charged metal cation and a negatively charged non metal anion

-fixed charge is when a metal cation that always forms an ion with the exact same electrical charge

-group 14’s first three 3 elements do not have a charge

-variable changes when a metal ion can form cations with different positive charge value’s depending on chemical reaction of compound

-you have to put roman numeral when you see transition metal

Polyatomic ions

charged groups of two or more atoms that act as a single unit with a next positive or negative charge

Hydrates

a compound that has water molecules trapped inside its core structure or crystal latticec

covalent compounds

-all non metals

Nomenclature of Binary ionic Compounds

-Metals give off electrons and form cations in ionic compounds

-Nonmetals pick up electrons and form anions in ionic compounds

-Cation name=name of element

-Cation charge=group number

-Anion name=element name with the ending replaced by the suffic “ide”

-Anion charge=Cgroup number

Metals with More than One Oxidation State

-Oxidation State: +1,+2,+3,+4,+5,+6,+7,+8,

-Roman Numeral: I,II,III,IV,V,VI,VII,VIII

-The cations from group 1A and 2A metals always have charges of +1 and +2 so roman numeral is not used in their names

Ag+=Silver

Zn²+=zinc

Cd²+=cadmium

Al³+=aluminum

Nomenclature of Ionic Compounds with Oxo Anions (Oxyanions)

-Oxo anions, or oxyanions, are composed of an element with one or more oxygens attached to it

-Never break the oxo anion up into elements

-Always have the “ate” or “ite” ending

-Ate Anions to know

Nitrate	NO3 -
Acetate	CH3COO -
Chlorate	ClO3 -
Carbonate	CO3 2-
Sulfate	SO4 2-
Chromate	CrO4 2-
Phosphate	PO4 3-

Nomenclature of Ionic compounds (oxoanions)

ate anion		ite anion
Nitrate	NO3 -	Nitrite	NO2 -
Acetate	CH3COO -
Chlorate	ClO3 -	Chlorite	ClO2 -
Carbonate	CO3 2-
Sulfate	SO4 2-	Sulfite	SO3 2-
Chromate	CrO4 2-
Phosphate	PO4 3-

-If there is one more oxygen than the ‘ate’ anion, use the prefix per

-If there is one fewer oxygen than the ‘ite’ anion, use the prefix hypo

-Ex: Chlorate=CIO3= Perchlorate CIO4^-

More anions to learn

Cyanide=CN^-

Hydroxide=OH^-

Hydrogen Carbonate/Bicarbonate=HCO3^-
Hydrigen Sulfate/Bisulfate=HSO4^-

Binary Acid Nomenclature

	Formula	Molecular Name	Acid Name
Strong Binary Acids	HCl	hydrogen chloride	hydrochloric acid
	HBr	hydrogen bromide	hydrobromic acid
	HI	hydrogen iodide	hydriodic acid
Weak Binary Acids	HF	hydrogen fluoride	hydrofluoric acid
	H2S	hydrogen sulfide	hydrosulfuric acid
	HCN	hydrogen cyanide	hydrocyanic acid

Oxoacid (Oxyacid) Nomenclature

ate anions form	ic acids.	HNO3 =	nitric acid
ite anions form	ous acids.	HNO2 =	nitrous acid

	Anion Name	Anion Formula	Acid Name	Acid Formula	Kind
ate anions	nitrate	NO3 −	nitric acid	HNO3	strong acids
	perchlorate	ClO4 −	perchloric acid	HClO4
	sulfate	SO4 2−	sulfuric acid	H2SO4
	acetate	CH3COO−	acetic acid	CH3COOH	weak acids
	carbonate	CO3 2−	carbonic acid	H2CO3
	phosphate	PO4 3−	phosphoric acid	H3PO4
ite anions	nitrite	NO2 −	nitrous acid	HNO2
	hypochlorite	ClO−	hypochlorous acid	HClO
	sulfite	SO3 2−	sulfurous acid	H2SO3
	phosphite	PO3 3−	phosphorous acid	H3PO3

Naming and identifying Isotopes

-Atomic number determines the number of protons, so they are written as subscripts.

Ion formation

-occurs when neutral elements react

Ionic solids

-Ionic Solids contain oppositely charged ions

-can consist of simple ions or polyatomic ions

Metal

-Efficient conductors of heat and electricity, malleable and ductile

-Have a lustrous appearance and tend to lose electrons to form positive ions

Nonmetals

-lack the physical properties that characterize metals

-tend to gain electrons in reactions with metals to form negative ions

-often bond to each other to form covalent bonds

Alkali metals

Group 1A

-very active elements that readily form ions with a 1+ charge when they react with non metals

Alkaline Metals

Group 2a

-forms ion with a 2+ charge when they react with non metals

Halogens

Group 7A

-form diatomic molecules (chemical structure of exactly 2 atoms)

-react with metals to form salts containing ions with a 1- charge (expect asatine)

Noble gases

-exist under normal conditions as monoatomic gases

-have little chemical reactivity

Joseph Proust

-Laws of definite proportion

-A give compound always contain exactly the same proportion of elements by mass

-Ex. H2O, there is always one hydrogen with 8 grams of oxygen

John Dalton

-Law of multiple proportions

-When two elements form a series of compounds, the ratios of the masses of the 2nd element combine with 1 g of the 1st element can always be reduced to small whole numbers

Dalton’s atomic theory

-Each element is made up tiny particles called atoms

-Atoms of a given element is identical

-atoms of different elements are different in same fundamental way or ways

Chemical compounds

-a given compound always has the same number of atoms and types of atoms. (law of definite proportions)

-Constant chemical composition means that a specific pure substance is always made of the exact same ingredients in the exact same amounts, no matter where you find it or how it was created.

Milikan

-experiment involved charged oil drops that help determine the magnitude of electron charge

-to calc the mass of an electron as 9.11×10^-31 kg

Chadwick

-explained the missing mass in the nucleus and involved isotopes

-discovered neutrons and why isotopes exist in the nucleus

-An isotope is a form of a chemical element that has the same number of protons but a different number of neutrons in its nucleus

-Isotopes exist because an atomic nucleus can hold different number of electrons while keeping the exact same # of protons

Boyle

-performed quantitative experiments to measure the relationships between the pressure and volume of air

JJ Thompson

-Suggested that cathode rays was a stream of negatively charged particles (electrons)

-cathode rays was produced at the negative electrode when high voltage was applied to the tube, repelled by negative pole of an applied electric field

-plum pudding model, where negative electrons sit inside a sphere of positive charge.

Types of Radioactive Emission

-Gamma Rays: high energy light

-Beta particles: high speed electrons

-Alpha particles: particles with 2+ charge, mass is 7300x that of the electron

Rutherfold’s experiment

-If atoms are spheres of diffuse positive charge, the particles would have passed through the foil unobstructed

-Some particles were deflected at sharp angles, which lead to the conclusion that they collided with something in their path

-Determined that atom is mostly empty space with a tiny and dense nucleus that contains most of the atom’s mass and all of its positive charge

-Neutrons are located in the nucleus of the atom

-Mass of proton is orders of magnitude larger than the mass of an electron because mass of an atom is concentrated in its nucleus

-Neutrons and protons account for most of the mass of an atom (located in the nucleus)

Chemical bonds

-forces that hold atoms together in compounds

-collection of atoms is called a molecule

-it can represent chemical formula, structural formula, space filling model, and ball and stick model

Ion

-atom or group of atoms with a net positive or negative charge