Chemistry- atoms, and their history

basic information about atoms, and the periodic table.

law of definite proportions

a given compound always contains exactly the same proportion of elements by mass

Conversation of mass

When matter changes the total mads is the same as total mass of reactants

atomic mass

Number of protons and neutrons

atomic number

of protons

mass number

the sum of the number of neutrons and protons in an atomic nucleus

Isotope

Atoms of the same element have different numbers of neutrons

Ions

Mean atom has lost or gained electrons

Democritus

Greek philosopher said all matter is made of tiny particles called "atomos" or atoms

Atomos

greek word for atom- means not able to be divided

John Dolton

developed the atomic theory

Atomic Theory (Dalton)

1. All matter is made of atoms
2. 2.(not true) atoms are indestructible and indivisible
3. compounds are combinations of different atoms

(Not true)

JJ Thomson

discovered electron with a cathode ray tube

Made plum pudding model

Ernst Rutherford

A discovered nucleus that most mass is in the nucleus

Did the gold foil experiment

Neils Bohr

\-said that electrons are in energy levels, discovered Energy levels with hydrogen gas

Used planetary models

Robert Millikan

Oil drop experiment

Discovered the charge of an electron

Sir James Chadwick

discovered the neutron

Explains why electrons move

Changed model

The nuclear notation

shows the atom's symbol, mass number, and atomic number

A

mass number A=Z+N

Z

atomic number (number of protons)

X

chemical symbol for the element

N

neutron number

hyphen notation

the mass number is written with a hyphen after the name of the element

Law of Multiple Proportions

Whenever two elements form more than one compound, the different masses of one element that combine with the same mass of the other element are in the ratio of small whole numbers.

Things we know about electrons

\-electrons farther from the nucleus have higher energy

* further levels can hold 2n2 electrons n=energy levels

Proton symbol

p+

Neutron symbol

n0

electron symbol

e^-

what holds the nucleus together

strong nuclear force

energy levels

The first energy level can hold 2 electrons

The second energy level can hold 8 electrons

average atomic mass

the weighted average of the atomic masses of the naturally occurring isotopes of an element

average atomic mass formula

(Percent to decimal)(mass) + (percent to decimal)(mass)

weighted averages

(abundance 1) * (mass 1) + (abundance 2) * (mass 2) + (abundance 3) * (mass 3)

Wener Heisenberg

Heisenberg Uncertainty Principle - Cannot know the speed and location of an electron at the same time.

Erwin Schrodinger

In 1926 developed the basic mathematical equation for quantum mechanics

nucleus size

small but massive(dense)

electron size

small and spread out

mole

the SI base unit used to measure the amount of a substance

molar mass

the mass of one mole of a pure substance

strong nuclear force

the powerful attractive force that binds protons and neutrons together in the nucleus