Ito po yung pag pipilian ng mga sagot:
NEGATIVELY
CHARGED PARTICLES
NEUTRAL
ATOM
MODEL
VERY SMALL
CLOUDS
PROTION
COMPOUND
ATOM
ELECTRONS


A Greek philosopher named Democritus said that all atoms are small, hard particles. He thought that

atoms were made of a single material formed into different shapes and sizes. The word "(1) ___________ " is

derived from the Greek word "atomos" which means "not able to be divided."

In 1803, John Dalton, a school teacher, proposed his atomic theory. Dalton's theory states that elements

(substances composed of only one type of (2) __________) combine in certain proportions to form (3)

__________.

In 1897, a British scientist named J. J. Thomson experimented with a cathode-ray

tube which had a positively charged plate. The plate attracted negatively charged particles

that we now call (4) ____________. Rather than being indivisible particles, Thomson's

plum-pudding (or raisin bread) atomic model states that atoms contain (5) ___________

charged electrons embedded within a sea of positive charge.

In 1909, Ernest Rutherford conducted an experiment in which he

aimed a beam of positively charged particles at a thin sheet of gold foil. Most

of the particles went straight through the gold foil, some were deflected and

others bounced straight back. Because some of the particles bounced straight

back, Rutherford was able to show that the center of the atom, the nucleus, is

(6)______________ and (7) ______________. The nucleus contains protons,

which are positively charged, and neutrons, which are (8) ______________.

In 1913, Niels Bohr, a

Danish scientist who worked with Dr. Rutherford, proposed that

electrons move around the nucleus in certain paths, or energy levels

(just like in the solar system where planets move around the sun). This

(9) ___________ was improved upon by an Austrian physicist named

Erwin Schröedinger and a German physicist named Werner

Heisenberg. Schröedinger and Heisenberg proposed that electrons

do not move in definite paths around the nucleus, but are be found in

regions around the nucleus called electron (10) _____________.

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