Science Standard III, Chemistry
Lesson 310, The Atom
Defining atom and element
Understanding the impact of Democritus on the discovery of the atom
Recognizing the main points of Dalton’s atomic theory: all elements are composed of atoms that cannot be divided or destroyed; atoms of the same element are exactly alike; atoms of different elements are different; compounds are formed when the atoms of two or more elements are joined
Describing Thomson’s atomic model: the “plum pudding” model: In it, negatively charged particles are scattered throughout a positively charged material
Describing Rutherford’s atomic model: positively charged particles form the small, dense center of the atom. This positively charged center is called the nucleus. Negatively charged electrons are scattered outside the atom’s nucleus.
Defining atomic mass
Knowing that different elements will have different atomic masses