Introduction to Chemistry Science 10

History Early Greeks thought matter could be subdivided forever. ~ 450 B.C. Empedocles suggested all matter was made of only 4 “elements” earth, air, water, and fire ~ 400 B.C. Democritus suggested all matter was made of atoms, tiny particles that cannot be broken down further. He was not believed! 1669 Hennig Brandt discovered phosphorus. He did not realize he discovered an element! Experimenters such as Robert Boyle, Henry Cavendish and Antoine Lavoisier produced gases such as oxygen and hydrogen.

John Dalton invented the modern atomic theory. Elements are all made up of extremely small particles called atoms. The atoms of each element are all identical, while atoms of different elements will have different properties. Each chemical compound is unique and consists of a particular combination of atoms. Chemical changes involve the reshuffling of atoms in a compound to make new compounds. Note: updates to Dalton’s original theory have been made as additional information was discovered.

+1 charge -1 charge 0 charge (neutral)

Pure substances A pure substance is a made up of only one type of particle. There are only two types of pure substances: Elements Compounds An element is a pure substance that cannot be separated into simpler substances by chemical processes. A compound is a pure substance that is composed of two or more different atoms combined in a specific way.

Checkpoint Question #1 An element is a pure substance. True False

Checkpoint Question #1 An element is a pure substance. True False

Subatomic Composition of Atoms An atom is the smallest possible piece of an element which still has the properties of the element. A subatomic particle is a particle that makes up an atom. Location Mass Charge protons neutrons electrons 1 amu ~ 0 amu + 1 -1 nucleus orbitals around nucleus Amu = atomic mass unit

Summary

The Nucleus The nucleus is at the centre of an atom. The nucleus is composed of protons and neutrons. Electrons exist in the space surrounding the nucleus.

The Nucleus # of protons = # of electrons in every atom Atomic number = # of protons = # of electrons Atomic mass = protons + neutrons Hint on how to find neutrons: Neutrons= atomic mass – protons

How do you find it?? Atomic number Ion charge Symbol Name Atomic Mass

Checkpoint Question #2 What is the atomic number of Potassium? A)36 D) 19

Checkpoint Question #2 What is the atomic number of Potassium? A)36 D) 19

Periodic Table: Period 1 Period 2 Period 3 Period 4 Period 5 Period 6 Elements are organized by atomic number (# of protons) Left  Right across each row. Each row is called a period. Period # = # of electron shells in an atom. Period 1 Period 2 Period 3 Period 4 Period 5 Period 6 Period 7

Each column is called a group or family. Elements in the same group have similar chemical properties. Group 1: Alkali Metals Very reactive metals 2: Alkaline Earth Metals Somewhat reactive metals 3-12: Transition Metals 17: Halogens Very reactive non-metals 18: Noble Gases Very unreactive gaseous non-metals Last digit of group # equals the # of valence electrons in the atom. (coloured groups only, not including transition elements) 1 17 18 2 13 14 15 16 3 4 5 6 7 8 9 10 11 12

Checkpoint Question #3 Which period is Iodine found in? 4 1 5 8

Checkpoint Question #3 Which period is Iodine found in? 4 1 5 8

To do in class: 1. Periodic Table Scavenger Hunt 2 To do in class: 1. Periodic Table Scavenger Hunt 2. Practice (for homework if not done) 3. Review for Ch.12 Plate Tectonics!

Bohr Model of Atomic Structure Shows all electrons in each energy level around the atom. Atomic number = protons Oxygen At. # = 8 8 protons 8p Atomic mass = protons + neutrons 8n Oxygen mass = 16 8 neutrons Note: a neutral atom has no overall charge. protons (+) = electrons (-) Oxygen 8 protons = +8 8 electrons (-8)

Assignment In Class: Atomic Structure Worksheet Homework: Electron Configuration Worksheet (leave Combining Capacity Column blank)