Bellringer Zinger Vocab recall! Tell me some of the words and definitions that you remember from Monday.

Matter is Made of Atoms Chapter 2 2014

Atoms and their Structures

Early Ideas about Matter First, from Greek philosophers, it was believed: Matter was a combo of air, earth, fire, and water Also pondered, was is the smallest particle? Later, Democritus, a philospher, proposed in 400BC: The world is made of empty space and tiny particles called atoms. (Cool info: ~360BC, Aristotle said… No. He didn’t believe that the empty space could exist Since he was so influential, Democritus’ theory was rejected.) Atoms- the smallest particles of matter and different types of atoms exist for every type of matter. Atomic theory- matter is made of fundamental particles called atoms Democritus

Modern Atomic Theory In 1782, Antoine Lavosier (French guy) was another philosopher who made measurements of chemical reactions in sealed containers. He concluded: Mass of reactants in container before a reaction equals the mass of the products after the reaction. The is known as the Law of Conservation of Matter (or mass)

Modern Atomic Theory (cont.) Go to page 51 (everybody please) Matter is neither created or destroyed but only changed. Look at example Figure 2.2 From the pictures, what are some hints that matter has not been destroyed in the reaction?

Modern Atomic Theory (cont.) In 1799, Chemist- Joseph Proust looked at water. He observed that composition of water is always 11.2% hydrogen and 88.8% oxygen by mass. Then he looked at other compounds and noticed that elements that compose compounds are also always in a certain proportion by mass. ---This is known as the Law of Definite Proportions Look at figure: 2.3 on page 52

Modern Atomic Theory (cont.) In 1803, John Dalton, studied the previous guys and determined that the atomic theory of matter must explain experimental evidence. Meaning that in chemical reactions, atoms are only rearranged. (no atoms form or disappear) Dalton’s Atomic Theory: 1. All matter is made of atoms. 2. Atoms are indestructible and cannot be divided into smaller particles. 3. All atoms of one element are exactly alike, but they are different from atoms of other elements.

Dalton gave chemists a model of the particle of nature of matter, but it raised new questions: If all elements are made of atoms, why are their so many different elements? What makes one atom so different from another atom? Late 19th century experiments suggested that atoms are made of even smaller particles.

The world around you….Atomic theory, conservation of matter, and recycling When waste is burned in a landfill, the atoms of the waste combine with oxygen or other substances to form new compounds. (atoms are recycled) Figure 2.4 (pg 53) By reusing the atoms, we conserve natural resources.

Back to notes: Discovery of Atomic Structure So, Dalton’s theory was almost correct. The theory was modified as smaller atomic particles were discovered. So let’s take a look at the 3 subatomic particles that determine different atoms and different atoms of the same element. In 1897, (British guy), J.J. Thomson discovered that the atom was not like a tiny solid ball that could not be broken down into parts like everyone thought. JJ Thomson

WKRP in Cinncinati The atom....

The Electron Thomson discovered the 1st subatomic particle, the electron. Electron- negatively charged particle of an atom

The Proton In 1886, another subatomic particle was discovered with a positive charge. Proton- positively-charged particle of an atom Atoms are made of the same number of protons and electrons.

Isotopes In 1910, it was discovered that an element (Neon) had atoms of two different masses. (See figure 2.7 on pg 60) Isotope- Atoms of an element that are chemically alike but differ in mass (Neon- 20 and Neon-22 or Carbon-12 and Carbon- 14) This led us to the discovery of the neutron, finally in 1930!

The Neutron Finally in 1930, the neutron was discovered. Neutron- a neutral particle of the atom.