Chemisty 4/10

empedocles
all matter composed of 4 elements: fire, water, air, earth. problem: breaking down never saw fire, water, air, or earth.
Democritus
400 B.C. theory on reason, thought if kept cutting atom eventually could not cut any more, or the properties would change. Thought matter was discontinuous (brick wall) and thought different kids of atoms existed for each different substance.
Aristotle
matter is continuous like concrete wall.
accepted until 1700s when people wanted proof
Dalton’s Atomic theory
1.all matter is composed of atoms
2. atoms of a given element are identical; atoms of different elements differ in these properties
3. atoms cannot be subdivided, created,or destroyed.
4. atoms of dif elements combine in simple, whole number ratios to form compounds.
5. in chem reactions, atoms are combined, separated or rearranged.
Thomson/crookes

crookes first, thomson around 1897,

1. glass tube with limited amount of gas in it, hooked up to an electricity source.

2. produced a florescence.

3. crooked thought it was radiation of some type and called fluorescence “cathode rays”

Thomson and Crookes’ findings

thomson discoverd that the cathode (f beam) were attracted toward a positively charged electrode, they are negative. They are particles because magnetic will only change direction of particles

disproved Dalton;s theory that atms are indivisible.

he cam up with plum pudding modle.

Rutherford

1911

what did he do?

 

aimed alpha particles at a thin sheet of gold foil

predictd they would go right through tfoil and most did, but some delected at various angles.

 

1. the atom is mostly empty space

2. a tiny, dense core in atom, this is why some deflected.

3. the core is positive b/c alpha were not attracted to it.

Rutherford

1911

conclusion

1. the atom is mostly empty space

2. a tiny, dense core in atom, this is why some deflected.

3. the core is positive b/c alpha were not attracted to it.


credited with discovering nucleus, positive, most of mass of atom.

Bohr

1913

Findings

improved rutherford’s model

1. answered question- why arent electrons pulled into positive nucleus if opposites attract?

2. bohr suggested that electrons are in orbit(now called energy levels) around the nucleus

3. Planetary atomic model

4. electrons located in orbits which ar different distances from nucleus

5. ELectrons have a certain amount of fixed energy, which prevents them from spiraling toward nucleus.

a. the futher the electron is from nucleus, the greater the energy of it

b. an atom is in ground state when all electrons occupy lowest energy levels (most stable)

c. electrons can absorb energy from outside source. When this happens, they move to higher enery levels, but are unstable.

Planck

particle nature of light

plancks constant: 6.626 x 10-34 J*s

used in E= hv

De Broglie

1942

thought there was wave nature of particles

  • electrons have wave properties as wel as particle
  • electrons are a “blur” or space filling

Heisenberg

1927

uncertainty principle

looks at electron as Particle

  • impossible to know exact location and velocity of electron
  • location is determined by bombarding electrons with photons. the collision changes the velocity of the elevtron. Opposite is also trye, trying to measure velocity will change its position.

Schrodinger

1926

wave equation; probabillity of finding an e-

looks at electron as wave

developed wave equation which could determine the probability of finding elevtrons in certain areas. they do not follow strict paths (bohrs model did)

calculations

;

lambda= h/ mass velocity

c=lambda nu

E= h nu

isotope

  • atoms with same number of protons and different number of neutrons
  • disproved point in dalton’s theory

ions

  • charged particle
  • Ca2+ cation positive loose 2 els
  • F anion negative increase 1 el

atomic number

  • gives element identity
  • # of protons
  • represented by z

Mass Number

  • number of protons and neutrons
  • represented by A
  • neutral
  • A/Z X

subatomic particles — location, relative mass, charge

Protons: nucleus, positive, 1

Neutrons: nucleus, neutral, 1

Electrons:outside nucleus, negative, 0

group vs. period

groups are vertical

periods are horizantal

Location

Alkali metals, alkaline metals, noble gasses, halogens, transition metals, main group elements, metals, metalloids, nonmetals

[image]
s p d f blocks
[image]

quantum number 1

represents:

which describes:

how many?

symbol:

values:

represents: energy level

which describes: relative size of electron cloud

how many? 1-7

symbol: n

values: positive integers

quantum number 2

represents:

which describes:

how many?

symbol:

values:

represents: sublevels

which describes: shape of electron cloud

how many? 4 spdf

symbol: l

values:0 -> n-1

other info: energy level = # of sublevels

quantum number 3

represents:

which describes:

how many?

symbol:

values:

represents: orbital

which describes: orientation of electron cloud

how many? s -1 p-3 d-5 f-7

symbol:ml

values: -l to l

other info: orbital — amount of space occupied by a maximum of 2 electons.

quantum number 4

represents:

which describes:

How many:

symbol:

values:

represents: spin

which describes:direction of electron spin

how many? either clockwise or counter

symbol:ms

values:+1/2 or -1/2

other info: electrons in the same orbital must have opposite spins

ground state vs. excited

ground is stable

excited is not

atoms vs. ions

atoms have no charge

ions have a charge

valence electrons

Na – [Ne]3s1 1 val e-

P – [Ne]3s23p3 5 val e-

Pb- [Xe]6s24f145d106p2 4 val e-

Fe- [Ar]4s23d6 2 val e-

exceptions to d4 and d9

which elemts is this for?

elements: chromium, molybdenum, copper, silver, gold

d4 -> d5

d9 ->d10

isolectronic species

have similar electron configurations

 

valence electrons
electrons in outermost energy level
what did Henri Becquerel discover?
radiation
the beam of light

had negative charge particles

negative b/c drawn to positive

 

positive beam different defractions

not the same mass

x

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