Atoms and Elements

Indirect Evidence

Evidence from behavior rather than seeing or touching it
(Like an inferance)

Greek Model of the Atom(Democritus)

Atom is the smallest possible piece of matter

Protons

Positively charged particles located in the nucleus

Nuetrons

Nuetral particles located in the nucleus

Electrons

Negatively charged particles arranged in energy levels
(K.L.M ect. which orbit the nucleus)

Rutherford

-Atom is mostly empty space
-Electrons scattered around edge
-Positively charged nucleus
-Gold Foil experiment led to this model

Thomsan

Positively charged particles scattered throughout negatively charged electrons

Dalton

-Atoms are indivisible and indistructable
-Atoms of the same element are the same
-Atoms of a different element are different
-Compounds form by joining atoms of two or more elements

Bohr

Energy levels are located certain distances from the nucleus

Atomic Number

Number of protons in the nucleus of an atom

Isotope

Atoms of the same element that differ by their mass number

Mass Number

The sum of the proton and nuetron in the nucleus of an atom

Atomic Mass

The average mass of all the isotopes of that element in the proportion that they occur in nature

Quarks

Elementary Particles

Strong Force

-Opposes the electromagnetic force of repulsion between protons
-holds the nucleus of the atom together
-greatest of all four atomic forces but has limited range

Weak Force

-Responsible for radioactive decay
-During radioactive decay a nuetron changes into a proton and an electron

Electromagnetic Force

-Can either attract or repel the particles on which it acts
-Opposite charges attract
-like charges repel

Gravity

-Weakest force known in nature
-The force of attraction between all objects in nature