Chemistry unit 2

Democritus

First discovery, found things were composed of particles,(earth, air water,)

Dalton

1st Agreed with Democritus, but his elements were more defined. Discovered atomic theory

• spherical model: atoms → sphere w/ positive charge & neg electrons (no nucleus)

Atomic theory (dalton)

1. Everything is composed of indivisible atoms

2. All atoms in elements are identical with the same mass

3. Compouds are combinations of 2 or more different types of atoms (Law of multiple porprtion)

4. Atoms neither created or destroyed in chemical reactions → reorganized (Law of conservation of mass)

JJ Thompson

2nd used cathode ray to show negative particles, discovered electrons

• plum pudding model - atom is a sphere of positive charge, with negatively charged electrons in it

Rutherford

• 3rd Agreed with thompson

• gold foil experiment → discovered nucleus

• Theorized all atoms were unstable

  • nucleur model - small pos nucleas surrounded by electrons

Neils Bohr

• 4th found electrons are not surrounding nucleus randomly

  • Travel in orbits

• discovered orbits have specific energy states

• quantum levels

• Bohr model - electrons in orbid around nucleus

De Broglies

• found electrons are negatively charged waves

Erwin Schrödinger

• probability model

• electrons are a cloud around nucleus

  • Quantum model: electrons r clouds around nucleus (dots)

nucleus

center of atom & contains its mass

protons (p+)

positive, contain one atomic mass unit per proton (amu)

electrons(e-)

Atomic number(z)

number of protons in nucleus

Mass number(A)

protons + nuetrons (not on periodic table)

Average atomic mass

weighted mass of all isotopes of an element

• AAM = Mass A(A%)+Mass B(B%) + …

*round to 2 decimal places after

Chemical reactions

atoms attain stability by losing, gaining, or sharing electrons

Nuclear reaction

Atoms attain stability through changes in nucleus

radio activity

when unstable nucleus spontaneously emits energy/rays to be more stable

• radioactive decay

radioactive isotope

isotope with unstable nucleus

strong nucleur force

attractive force that binds protons & nuetrons together in nucleus

electrostatic repulsion

protons repulsing eachother

The heavier the nucleus ___

the more their proton to nuetron ratio increases

• repulsive electrostatic force increases faster than nuclear → higher change un unstablititly

• elements above #83 - unstable & radioactive

Alpha decay

• least energetic

• 4/2 He

• Charge: 2+

Beta decay

• nucleus release electron

• 0/-1e

• charge:-1

Gamma radiation

• most energetic

• 0/0 Y, 0

• just radiation

How to stop alpha decay

weak, paper works

How to stop gamma decay

Strong, lead helps but not fully

How to stop Beta decay

Aluminum works

positron emission

• Opposite of negative electron

• 0/1+

• 1+ charge

nuetron emision

1/0 N

proton emission

1/1P

electron capture

0/-1 e

• electron plus proton makes nuetron

Empirical formula

lowest whole number ratio of atoms in a compund

• ex: C6H6 → CH

molecular form

actual formula of molecular compound

• ex: C6H6

order of atomic discoveries

Deomocritus → Dalton → JJ Thompson → Rutherford → Neil Bohr → Erwin Schrödinger