Chemistry-Chapter 3.3 and Scientists that contributed to the Atoms

Atoms

smallest particles of an element that has properties of the element, made of 3 basic subatomic particles(protons, neutrons, and electrons)

Atomic Mass Unit(AMU)

A metric unit used to measure the mass of very small objects, such as particles and atoms (1 amu=1/12 the mass of one carbon-12 atom)

Proton

1+ charge, its location is the nucleus, its relative mass is 1, and its importance is that it determines the identity of an element.

Neutron

No charge, its location is the nucleus, its relative mass is 1, and its importance is that it supplies proper mass to hold nucleus together.

Electron

-1 charge, its location is in space around the nucleus, its relative mas is 1/1840, and its importance is that it determines bonding and reactivity

The nucleus

What contains almost the entire mass of the atom?

Atomic number

Number of protons in the nucleus of an atom, identifies the element, in a neutral atom, equals the number of electrons

Mass number

Number of particles that gives atoms its mass, mass number= # of protons + # of electrons (Its not on the periodic table)

Isotopes

Atoms of the same element with different numbers of neutrons(and thus different masses), Isotopes names contain the element name and the mass number (Ex: Carbon-14)

Relative Abundance (natural abundance)

Most elements found naturally as a mixtures of isotypes, it is consistent regardless as a percentage( Ex: Carbon-12 98.9%)

Atomic Mass (atomic weight)

Decimal value given on most periodic tables(atomic mass= ( # of Neutrons + # of protons)

For an element it is the weighted average of all Isotopes of an element, for an individual atom, it is the total number of # of Neutrons + # of Protons

What is the different between atomic mass in a element and individual atom?

democritus

began search for matter 2400 years ago, believed all matter is made up of a small, hard particle that could not be divided, ideas were later discredited, gave particles the name "atmos"

John Dalton

Ideas on atomic theory included: • MATTER IS COMPOSED OF SMALL PARTICLES CALLED ATOMS, ALL ATOMS OF AN ELEMENT ARE IDENTICAL TO EACH OTHER AND DIFFERENT FROM ATOMS OF
OTHER ELEMENTS ,ATOMS CAN NOT BE CREATED, DESTROYED, OR
DIVIDED, ATOMS ARE REARRANGED IN A CHEMICAL REACTION

J.J Thomson

PERFORMED CATHODE RAY TUBE EXPERIMENTS
TO DISCOVER THE ELECTRON (1896-1897), DEVELOPED THE PLUM
PUDDING MODEL OF THE ATOM THAT CONSISTED OF A SOLID POSITIVELY CHARGED CORE WITH NEGATIVELY CHARGED PARTICLES EMBEDDED

Robert Millikan

PERFORMED THE OIL DROP EXPERIMENT THAT ALLOWED
HIM TO DETERMINE THE EXACT CHARGE OF AN ELECTRON (1909) ,NO NEW MODEL OF THE ATOM; HE AGREED WITH THOMSON’S MODEL

Ernest Rutherford

PERFORMED GOLD FOIL EXPERIMENT & DISCOVERED THE POSITIVELY CHARGED NUCLEUS (DUE TO PROTONS) (1911 DEVELOPED THE PLANETARY MODEL (OR NUCLEAR MODEL) WITH PROTONS IN NUCLEUS SURROUNDED BY ELECTRONS TRAVELING
IN ORBITS AROUND THE NUCLEUS RUTHERFORD REASONED
THAT ALL OF AN ATOM’S POSITIVELY CHARGED PARTICLES WERE
CONTAINED IN THE NUCLEUS. THE NEGATIVELY CHARGED PARTICLES WERE SCATTERED OUTSIDE THE NUCLEUS

James Chadwick

• DISCOVERED THE EXISTENCE OF NEUTRONS AS THE PARTICLES THAT MADE UP THE REST OF THE MASS OF \THE NUCLEUS (1932) NO NEW MODEL

Niels Bohr

IN 1913, THE DANISH SCIENTIST NIELS BOHR PROPOSED AN
IMPROVEMENT. IN HIS MODEL, HE PLACED EACH ELECTRON IN A
SPECIFIC ENERGY LEVEL.