gen chem 1

Atom

comes from word atomos(not divisible)

Made of a positively charged nucleus surrounded by negatively charged electrons

Nucleus has protons and neutrons

Mass of proton = mass of neutron

Element

a substance that has a composition only corresponding to one of the symbols in the Periodic Table

Compounds

a substance containing multiple elements

Allotropes

different structural forms of the same element
i.e. Carbon w diamond, graphite
Oxygen with dioxygen and ozone(O3)

Phosphorus with red, white and black versions

Only elements, not compounds

Polymorph

different structural forms of the same compound in the same phase

Mixture

a combination of two or more elements/compounds

Homogenous mixture

a mixture in which the composition is uniform throughout

Heterogenous mixture

a mixture in which the composition is not uniform throughout

law of conservation of mass

mass is not created or destroyed in a chemical reaction

law of definite proportions

in a pure compound, the constituent elements are present in a definite proportion or % by mass

law of constant composition

all samples of a given chemical compound have the same elemental composition

law of multiple proportions

when two elements form a series of compounds, the masses of one element that combine with a fixed mass of the other element are in the ratio of small integers to each other

law of combining gas volumes

When gases react, they do so in a definite integer ratio by volume; volume of each product gas to the volume of either reacting gas is the ratio of simple integers

Avogadro’s hypothesis

Equal volumes of different gases at the same temperature contain equal numbers of particles; can be atomic, diatomic, or polyatomic

Particles and atoms are NOT equivalent

Cannizzaro

calculated the molecular mass of gaseous compounds

Molecules have whole number of atoms and equal volumes of gases under the same conditions haave the same number of molecules

Determined that some molecules must be diatomic

Dalton

a lot of theory

Discovered laws of definite and multiple proportions

Said elements are made of indivisible atoms, all atoms of an element are identical, different elements have different atoms, compounds are formed when unlike elements combine in small whole-number ratios, atoms retain their identities in chemical processes

Wrong because atoms are divisible and isotopes exist

Mendeleev

made modern periodic table and sorted everything by atomic masses

properties determine by atomic number

Rutherford

Gold foil experiment shooting positive alpha particles;

when they were deflected knew plum pudding model was false

Concluded that most mass was the positive nucleus with electrons surrounding it

JJ Thomson

Cathode ray experiment

Found charge to mass ratio of electrons(-1.76×10^8) and that the charge was negative

Thought atom had plum pudding model: electrons in a field of positive charge

Millikan

Oil drop experiment

Found the charge of the electron (1.6×10^-19) and deduced mass from it(9.11×10^-31)

Atomic number

The number of protons an element has

Mass number

Number of protons and neutrons

Isotopes

nuclides of the same element with different mass numbers

Ionic bond

Atoms bound by transferring electrons to form charged atoms(ions)

Cation

positive ion from losing electrons

Smaller than og

Anion

Negative ion from gaining electrons

Bigger than og

Covalent bonds

Atoms bound by sharing electrons

Metals

have luster

are good conductors of heat and electricty

malleable

ductile

Nonmetals

dull color

poor conductor of heat and electricity

brittle

Alkali metals

Li, Na, K, Rb, Cs, Fr

Reactive with water to make alkaline solutions

Ignite or explode near water

Soft metals that can be cut with a knife

Malleable and ductile

Forms M+ ions

Alkaline earth metals

Be, Mg, Ca, Sr, Ba, Ra

Oxides are insoluble in water and stable to heat

Harder and less reactive that alkali metals

Forms M2+ ions

Boron family(triels)

B, Al, Ga, In, Tl

From semimetallic to metallic

Forms M3+ compounds or monovalent compounds

Carbon family

C, Si, Ge, Sn, Pb

From nonmetallic to semimetallic to metallic

Tetravalent and divalent compounds

Pnictogen

N, P, As, Sb, Bi

From nonmetallic to semimetallic to metallic

Chalcogens

O, S, Se, Te, Po
Nonmetallic to semimetallic

Forms oxides and sulfides

Halogens

F, Cl, Br, I, At

Diatomic nonmetals

Melting point increases down the group

Noble gases

He, Ne, Ar, Kr, Xe, Rn

Very unreactive because full octet

Avogadro’s number

6×10²³ in 1 mole

Volume occupied by molecular mass in grams

Avogardro * volume of one molecule

Mole

Avogadro’s number as a unit

= mass/molar mass

Mass of a mole in amu = mass of mole in grams

amu

1g/avogadros number = 1.66×10^-24

Molar mass

mass of 1 mole = to molecular mass in g/mol

STP

Standard temperature and pressure(0C and 1atm): 1 mole of gas takes up 22.4 L

Limiting reactant

The reactant that is used up first

Determined by smallest value of moles/x or mass of X/x(molecular weight of X)

Molecular formula

specifies number of atoms of each element in one molecule

Empircal formula

simplest formula that gives the correct relative number of atoms; can be equal to molecular

Percent yield

actual/theoretical yield * 100

Theoretical yield

moles of limiting reactant * ratio between reactant and product * molar mass of product

Ionization energy

the tendency of an atom to give up an electron

Positive

Electron affinity

tendency of an atom to receive an electron

Most are negative except Group 2 and 8

Change in energy

Energy of products- energy of reactants

Positive means energy is required to effect the transformation(unfavorable)

Negative means energy is released during the transformation(favorable)

Bond energy

energy required to break a covalent bond and separate the atoms

Average of 2 different elements bond energy is always less than the actual bond energy of the 2 elements

Lattice energy

Energy needed to form an ionic solid or gaseous ions

k(Q1Q2/r)

Bond length

distance for which a molecule has the minimum

Electronegativity

the ability of an atom in a molecule to attract electrons to itself

An atom with greater electronegativity has more atoms and will make a polar bond

Increases from left to right, bottom to top

Electronegative atoms form negative ions, while electropositive atoms form positive ions

Ionic bonds have big differences, covalent bonds have small differences

Polarity

Occurs when atoms aren’t shared equally because of electronegativity

Dipole moment

u = Q x r

two charges of equal magnitude Q separated by distance r

Percent abundance

Average mass = (m1x)+(m2*(1-x))'

x is fractional abundance on first isotope

Atomic radius

Increases down a group and decreases from left to right

More protons means smaller radius

valence electrons

the electrons in the outermost shell

Octet rule

8 electrons are favorable for elements

Lewis dot

Put an atom in the center(usually electropositive)

Give outer electrons 8 electrons first

Count the number of electrons(number = number of electrons in neutral atom- formula charge)\

Move electron pairs to satisfy octet

Determine number of unused electrons

Other methods exist

Lone pair

Pair of electrons not bonded in an octet

Dative bonds

Atoms using formal charges to be able to bond

One electron donates a pair and another accepts

Formal charge

Group valence - number of electrons in lone pairs - number of bonds

Resonance structure

When a bond can be represented as a bond of multiple Lewis structures because the bond lengths are equal

Only electron position changes(line)

Degenerate when they are equivalent

Odd-electron molecules

Can’t form a full octet usually

Hypovalent molecules have less than an octet

Can use lone pairs for resonance structures

Valence expansion

Sometimes electrons have more than an octet

Just keep applying the octet rule

Oxidation number

Calculated for bonded atoms

Oxidation numbers add up to the charge on the molecule

Oxidation number is based on the number of electrons an atom gains for a full octet:(i.e, oxygen -2)

VSEPR Theory/molecular geometry

Valence Shell Electron Pair Repulsion

Repulsion between electron pairs is minimized

Noted as AXe(X is coordination numbers, e is lone pairs)

Coordination number

number of atoms bonded

Steric number

Coordination number + lone pairs

Amplitude

maximum displacement from the center

squared determines the intensity of the radiation

Wavelength(lambda)

the peak-to-peak distance

Inversely related to frequency

Frequency(v)

the number of wavelengths that pass a given point in 1 second

Inversely related to wavelength

Speed of light

c = frequency * wavelength

3 × 10^8

Electromagnetic radiation

Electric and magnetic fields moving perpendicular to each other and the propagation of light

Electromagnetic spectrum

From highest to lowest energy

Radio waves

Microwaves

Infrared

Visible

Ultraviolet

X-rays

Gamma rays

Blackbody

I = Constant * T^4

Increases with frequency does opposite of wavelength

Photoelectric effect

E = hv

h = plancks constant = 6.63 × 10^-34

Phi is the work function representing og energy that electrons have to overcome to escape

hv = KE- phi

KE = 1/2mv²

Atomic spectra

v = C(1/2²-1/n²)

Rybdberg:

1/lambda = Rh(1/n1²-1/n2²)

Bohr model

Electron moves in circular orbits about the nucleus

Only fixed sets of orbits are allowed and no energy is emitted

Electrons only pass from one orbit to another

angular momentum

n(h/2pi) = nH

H/2pi

Radius of orbit

n²ao

Energy of orbit

-Re(1/n²)

Resonance condition

For energy to be absorbed or emitted the frequency of the light corresponds exactly to the difference in energy

E = E2-E1