Atomicstructure

Best, most likely, greatest, except

[|California Sample Test]

**__Atoms__**
1. Which statement //best// describes the density of an atom’s nucleus? A The nucleus occupies **most** of its volume but contains **little** of its mass. B The nucleus occupies very **little** of the its volume and contains **little** of its mass. C The nucleus occupies **most** of its volume and contains **most** of its mass. D The nucleus occupies very **little** of its volume but contains **most** of its mass.

2. When comparing the nucleus to the overall diameter of an atom, which model below could //best// describe the size comparison? A. A flower head in the middle of a flower. B. A golf ball on the 50 yard line in the middle of a football stadium. C. A popcorn seed in a bucket of popcorn. D. A test tube in a beaker.

3. What is the //most effective// way to stop gamma rays? A. Newspaper B. Brick wall C. Automobile D. Lead apron

5. What was the //best// evidence that Rutherford found for him to propose his model of the atom?

__Mendeleev__
4. Dimitri Mendeleev was able to predict the properties of “gaps” or “holes” on the periodic table, even though the element had not yet been discovered. How did he do so? a. Mendeleev was a psychic. b. Mendeleev used the group/ period ratio. c. Mendeleev made predictions based on mass. d. Mendeleev made predictions based on properties of other elements in the same group.

The elements, if arranged according to their atomic weight, exhibit an apparent periodicity of properties. He expected the discovery of many yet unknown elements.

He realized that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table.

This method of arranging elements meant there were gaps in his horizontal rows or 'periods'. But instead of seeing this as a problem, Mendeleev thought it simply meant that the elements which belonged in the gaps had not yet been discovered. He was also able to work out the atomic mass of the missing elements, and so predict their properties. And when they were discovered, Mendeleev turned out to be right. For example, he predicted the properties of an undiscovered element that should fit below aluminum in his table. When this element, called gallium, was discovered in 1875 its properties were found to be close to Mendeleev's predictions. Two other predicted elements were later discovered, lending further credit to Mendeleev's table.

Modern day periodic tables are expanded beyond

Mendeleev's  initial 63 elements. Most of the current periodic tables include 108 or 109 elements. It is also important to notice how the modern periodic table is arranged. Although we have retained the format of rows and columns, which reflects a natural order, the rows of today's tables show elements in the order of Mendeleev's columns. In other words the elements of what we now call a 'period' were listed vertically by Mendeleev. Chemical 'groups' are now shown vertically in contrast to their horizontal format in Mendeleev's table.

It is also worthy to note that Mendeleev's 1871 arrangement was related to the atomic ratios in which elements formed oxides, binary compounds with oxygen whereas today's periodic tables are arranged by increasing atomic numbers, that is, the number of protons a particular element contains. Although we can imply the formulas for oxides from today's periodic table, it is not explicitly stated as it was in Mendeleev's 1871 table. The oxides ratio column was not shown in earlier