Bell Ringer 1 Get a piece of paper

Bell Ringer 1. Get a piece of paper and fold it so that you have three columns 2. On one column you will write what you already know about the structure of atoms 3. On the second column you will write down what you would like to learn about atoms and their structure 4. On the third column you will write down what you learned today about the structure of atoms

Atomic Structure

Early History of Science • Greeks (400 BC): First to explain why chemical changes occur

Early History of Science • Greeks (400 BC): Is matter infinitely divisible? Or made of small indivisible particles? • Demokritos and Leucippos (460 -370 BC): Matter is made of indivisible particles (atomos; which in greek means undivisible)

For the next 2000 years • Alchemy

Foundations of modern Chemistry • George Bauer (1494 -1555) Metals from metal ores • Robert Boyle (1627 -1691) First “Chemist” to perform truly quantitative experiments. He carefully measured the relationship between pressure and volume of air

Foundations of modern Chemistry • Antoine Lavoisier (1743 -1794) Father of modern Chemistry • French chemist who explained what happens during combustion reactions and verified the Law of conservation of mass • Published the first Chemistry textbook in 1789

Scientists follow the lead • Joseph Proust (1754 -1826) • French guy who, following Lavoisier’s way of carefully measuring during an experiment, came out with the principle of the constant composition of compounds • Later known s the Law of definite Proportions Ø A given compound always contains the same proportion of elements by mass

Scientists follow the lead • John Dalton(1766 -1844) • Analyzing the quantities of different compounds came out with the Law of multiple proportions Ø When two elements form a series of compounds, the ratios of the masses of the second element that combine with 1 gram of the first element can always be reduced to whole numbers • First Atomic Theory 1. 2. 3. 4. Each element is made up of tiny particles called atoms The atoms of a given element are identical Chemical compounds form when atoms of different elements combine. A given compound always has the same number of and types of atoms. Chemical reactions involve reorganization of the atoms-change in the way they are bound togethre. The atoms themselves are not changed.

Scientists follow the lead • • Joseph Gay Lussac (1778 -1850. French) Amadeo Avogadro (1776 -1856. Italian) • Studied gases and came out with Avogadro’s hypothesis Ø At the same temperature and pressure, equal volumes of different gases contain the same number of particles.

Scientists follow the lead • J. J. Thomson(1856 -1940. English Physicist) • Discovered electrons using a cathode-ray tube • Led him to come out with the plum pudding model of the atom

Scientists follow the lead • Robert Milikan (1868 -1953) • In 1909 at the university of Chicago, performing very clever experiments with oil drops he was able to determine the mass of an electron. (9. 11 x 10^-31 kg) • Ernest Rutheford (1871 -1937. New Zealand) • Proved the plum pudding model wrong and discovered that atoms have a positive center.

Modern View of Atomic Structure

Modern View of Atomic Structure