Module 4 Review . Module 4 Review. Module 4. 01 Atomic Theory Review. * Matter- is anything that has mass and takes up space. *Element- substances could not be divided into other substances by any means. *Atom - The smallest unit of an element
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*Scientists still hold this to be true. All matter that has been studied and observed seems to be made up of atoms.
*All atoms of a given element are the same.
*We now believe that atoms of the same element have the same number of protons. However, you will learn in later lessons that atoms of the same element may have different numbers of neutrons. Atoms with the same number of protons and different number of neutrons are called isotopes.
*Different elements are made up of different atoms.
*Scientists still hold this statement to be true. Atoms of different elements have different numbers of protons. The number of protons in an atom is used to identify the element.
*At the beginning of the 20th Century, Thomson’s atomic model was accepted as the correct representation of the atom. In Thomson’s model, negatively charged electrons were dispersed inside an area of positive charge. The positive and negative charges canceled out each other, resulting in a neutral atom.
an English scientist, designed an experiment to test Thomson’s atomic model. Rutherford planned to fire heavy, positively charged, fast particles on a very thin metal foil, made of gold. A screen was placed around the gold foil. This foil was sensitive to particles that were fired and would show how the particles were affected by the foil. This set up was like firing a heavy cannon on a tissue paper. Rutherford did not expect the particles to get effected at all.
*Bohrstated electrons used specific orbits while moving around the nucleus. An electron could jump to a higher orbit if it gained energy or a lower orbit if it lost energy. Bohr’s model meant laws of classical physics did not apply to atoms. Bohr’s model was the beginning of a new field of study, called quantum physics.
*Rutherford proved the atom had a very dense core by his gold foil experiment. Investigating further, scientists discovered that an atom consisted of a nucleus containing protons and neutrons, and electrons that orbit around that nucleus
*In 1869, Dmitri Mendeleev, a Russian chemist, set out to organize the known elements according to their properties. He noticed that when elements were arranged by increasing mass, there were repeated or periodic patterns in their properties.
*homo-: This part of the word comes from the prefix hom-, which means same. A homogeneous sample is the same throughout the sample.
*–geneousin homogeneous: This part of the word comes from the root gen(os). In this context, it means kind. This helps us understand that a homogeneous substance is of the same kind throughout. It is uniform in its composition.
*hetero-: This part of the word comes from the prefix heter(o)-, which means different or other. A heterogeneous substance is different in various portions of the sample.
*–geneousin heterogeneous: This part of the word comes from the root gen(os). In this context, it means kind. This links with the prefix to tell us that a heterogeneous substance is of a different kind throughout. It is not uniform in its composition.
*An extensive physical property depends on the amount of matter present in the sample. Such properties include mass, length, shape, and volume. These measurements will change depending on how large or small the sample of matter.
*Intensive Physical Properties
An intensive physical property does not depend on the amount of matter present in the sample. Such properties include melting point, boiling point, density, ductility, malleability, and color. These properties will not change for a given type of matter regardless of the sample size.
*Weight-is a measure of Earth’s gravitational attraction for matter. This means that weight is affected by both the amount of matter in the object and the amount of gravity pulling on the object. This is why the weight of an object changes on different planets.
*Mass -is a measure of the quantity, or amount, of matter in an object. This means that the more matter there is in an object, the greater its mass. Mass is not affected by gravity. This is why the mass of an object does not change on different planets.