unit 2 full review

Atom

basic unit of matter, 118 types

element

simplest substance, made of only 1 type of atom

“seeing atoms”

STM magnified 10^8x

English/Latin

Origins of element names

allotrope

a different form of an element

oxygen allotropes

oxygen gas (O2), ozone (O3)

carbon allotropes

graphite, diamond, buck minster fullerene

compound

composed of at least 2 different atoms bounded together

pure substance

have a constant composition, elements and compounds

mixture

2 or more pure substances physically mixed together (not bounded)

can be separated by physical means (eg. distillation, filtration)

homogenous mixture

components are uniformly distributed (looks same throughout)

examples of homogenous mixtures

salt water, air, 14 karat gold (also example of alloy)

alloy

mixture of a metal with 1 or more elements

heterogenous mixture

components are not evenly distributed (you can see different components)

examples of heterogenous mixtures

oil and water, orange juice, blood

distillation

separation technique of a liquid mixture that depends on a difference in boiling points

for homogenous mixtures (solutions)

filtration

separation technique of heterozygous mixture

depends on size of particles

properties of matter

physical property, chemical property

physical property

can be observed without changing the chemical identity

examples of physical property

mass, volume, color, melting point

physical change

affects only the physical properties

example of physical change

ice (H2O) —> water (H2O) —> steam (H2O)

chemical property

observed when a substance reacts

chemical change (aka chemical reaction)

process that produces 1 or more new substances

evidence of a chemical change

gas is produced, precipitate is formed, heat is absorbed or released, light is released, color change

precipitate

insolvable solid produced when 2 clear liquids react

elephant toothpaste demo

H2O2 —> (NaI) H2O(l) + O2 (g)

NaI

catalyst (speeds up a chem reaction)

paper chromatography

process used to separate components of a mixture

absorbent

attracts and absorbs the materials to be separated

solvent

carries the materials to be separated

capillary action

solvent “climbs up” the absorbent

democritus, ancient Greece, 400 BCE (idea)

The idea that all matter is composed of atoms

Atoms

uncuttable

laws lead to 1st atomic theory

Law of definitie proportions, law of conservation of mass, law of multiple proportions

Law of definite proportions

any sample of a compound always has the same composition

law of definite proportions example

water is always 11.2% H and 88.8% O

Law of conservations of mass

matter cannot be created or destroyed, only transformed

law of conservation of mass example

S+O2—>SO2

Law of multiple proportions

diffe3rent compounds have different mass proportions

law of multiple proportions example

N2O is different than NO2

John Dalton 1803

1st atomic theory that was based on evidence

Half true (John Dalton)

1. All matter is made of indivisible atoms

2. All atoms of an element are identical

True (John Dalton)

3. Atoms of different elements have different physical and chemical properties

4. Atoms of different elements combine in simple, whole number ratios to form compounds

5. Chemical reactions consist of the combination, separation, and rearrangement of atoms

Marble

Dalton’s atom, indivisible and no different parts

JJ Thomson (1897)

made cathode ray tube

Thomson discovery

tiny, negatively charged particles found in all atoms

Thomson conclusion

the atom is not indivisible, the atom could be broken down into smaller particles.

atoms are natural, so there must be something positive inside the atom to balance the change

Cathode ray tube

“Light” was affected by a magnet charged plates (attracted to +, repelled by -)

purpose of charge to mass ratio

determine the mass of the particles (1000x less than the mass of a H atom)

Plum pudding model

the electrons were embedded in a “sphere” of positive charge

Rutherford’s gold foil experiment results

1 in 8000 alpha particles bounced back

alpha particles

massive, positively charged particles released by radioactive materials

nucleus

rutherford’s discovery

rutherford’s atom

nucleur atom

nucleus is…

positvely charged, most of the atoms mass, tiny part of an atom’s volume, dense (2.3×10^14 g/cm³)

Isotopes

atoms with the same number of protons but different number of nuetrons

particles

electron, proton, nuetron

electron (abr)

e-

proton (abr)

p+

nuetron (abr)

n0

mass of electron

0.000549

mass of proton

1.007276

mass of nuetron

1.008605

electron location

electron cloud

proton and nuetron location

nucleus

ion

charged atom (or group of atoms)

cation

postively charged ion

union

negatively charged ion

(average) atomic mass

the mass of an atom, measured in atomic mass units amu

1 amu

1/12 the mass of a carbon -12 atom (1.66×10^-24g)

weighted average

atomic mass listed in the periodic table is —— of all naturally occurring isotopes