“A tomos” means uncutable
To Democritus (a Greek philosopher), atoms were_______, hard particles that
were all made of the same material but were _________shapes and sizes.
Atoms were ___________in number, always moving and capable of joining
together.
John Dalton’s Theory
1. He deduced that all ____________are composed of atoms. Atoms are
indivisible and indestructible particles.
2. Atoms of the ________element are exactly alike.
3. Atoms of __________elements are different.
4. ______________are formed by the joining of atoms of two or more
elements.
J.J.Thompson’s plum pudding Model
1. In 1897, the English scientist J.J. Thomson provided the first hint that an atom is
made of even ____________particles. Thomson studied the ___________of an
electric current through a gas. As the current passed through the gas, it gave off
rays of ______________ ______________ ___________________ which were
much lighter than the ____________ gas atoms.
2. Thomson concluded that the negative charges came from __________ the
atom. A particle smaller than an atom _______ . The atom was _____________!
3. Thomson called the negatively charged __________________ today known as
_________________.
4. Since the gas was known to be neutral, having no charge, he reasoned that
there must be _________________charged particles in the atom.
5. He proposed a raisin bun model of the atom. His model pictured a __________
charged ball like bun with _____________ charged ______________ embedded in
it like raisins.
Rutherford’s Model of atom:
1. Rutherford’s experiment Involved firing a stream of tiny positively charged
particles at a thin sheet of gold foil (2000 atoms thick)
2 Most of the positively charged “bullets” passed right through the gold atoms in
the sheet of gold foil without changing course at all.
3. Some of the positively charged “bullets,” however, did bounce away from the
gold sheet as if they had hit something _____________. He knew that positive
charges______________ positive charges.
4. Rutherford had discovered the nucleus --- the tiny, dense, positively charge of
the nucleus. A decade later, he established there must be two kinds of
_____________ inside the nucleus of an atom. One particle later is called a
___________ and had a __________electric charge and other particle is called
a_______________, which had ________electric charge.
Bohr’s atomic model
He proposed that electrons ____________the nucleus in ________ ________
________ or __________. This means that each electron has ____________
amount of energy. He proposed that when electricity is applied to electrons, they
__________from _______energy level to___________. When they __________
back from ___________energy level to _____________ energy level, they release
___________ energy in the form of__________ _________________.