Intro to Atoms Atoms: the basic particle in which all elements are made Nucleus: The central core of an atom containing protons and neutrons In the nucleus are: Proton: small, positively charged particle in the nucleus of an atom ( + symbol) Neutron: Neutral charged particle in the nucleus of an atom Outside the Nucleus: Electron: tiny, negatively charged particle that moves around the nucleus of an atom

Law of Conservation of Matter Law of Conservation of Mass Laws of Science Law of Conservation of Matter Matter cannot be created or destroyed Law of Conservation of Mass Established by French Chemist Antoine Lavoisier In a chemical reaction, the mass of the products equals the mass of the reactants. THIS IS EXTREMELY IMPORTANT WHEN BALANCING EQUATIONS

What’s the MATTER. Matter: anything that has mass and takes up space What’s the MATTER? Matter: anything that has mass and takes up space. Mass: measurement of how much matter is in an object Element: a substance that cannot be broken down into any other substances by chemical or physical means Compound: a substance of 2 or more elements Mixture: 2 or more substances that are mixed together, but NOT chemically combined

Atomic Models Early Models/Theories of the Atom: Dalton’s Atomic Model: - All matter is composed of atoms - Atoms cannot be made or destroyed - All atoms of the same element are identical - Different elements have different types of atoms - Atoms of 2 or more elements can join together to form a compound

Modern Atomic Model – NOT ON YOUR PAPER! Electrons form a negatively charged cloud around the nucleus Cannot determine the location of an electron at any given time

Atomic Models continued… JJ Thomson’s Model: Atom is positively charged Discovered Electrons Rutherford’s Model: Protons and the nucleus Electrons orbit around the positively charged nucleus Chadwick’s Model: Discovered neutrons Bohr’s Model: Electrons move in specific layers (shells) Electrons move when atoms absorb or give off energy, moving from one shell to another

Atoms and Elements Atomic number number of protons in an element Number of electrons the element has Atomic mass: mass of one atom of the element How to calculate neutrons: atomic mass # - atomic number Valence electrons: electrons that can be transferred from one atom to another or may be shared between atoms Chemical symbol: symbol for element (H – Hydrogen) (C – Carbon)

Periodic Table Dmitri Mendeleev Created first Periodic Table Arranged elements in order of increasing atomic mass Placed similar elements in the same group according to their reactions Periods: a horizontal row in the P.T. Groups: vertical columns in the P.T. – also known as families due to similar characteristics

Groupings Metals (Alkali , Alkali Earth) Nonmetals Nobel Gases Transition Elements Halogens Common Elements

Valence Shells Group 1 = 1 valence electron Group 2 = 2 valence electrons Group 13 = 3 valence electrons Group 14 = 4 valence electrons Group 15 = 5 valence electrons Group 16 = 6 valence electrons Group 17 = 7 valence electrons Group 18 = 8 valence electrons (full shell)

Properties of Metals Classified by its physical properties such as shininess, malleability, ductility, and conductivity. Malleable: can be hammered flat or into other shapes Ductile: can be pulled out into a long wire Conductivity: ability to transfer heat from one object to another

Metals continued… Chemical properties: ability of a pure substance to change into another substance. Reactivity: The speed in which an element combines or reacts with other elements Corrosion: the wearing away of metal due to a chemical reaction Metals can be considered an alloy which is a mixture of a metal with one other element (usually found together in nature)

Physical and Chemical Properties Def: a change that does not result in the formation of any new substances Examples: Dissolving sugar in water Melting ice cubes Boiling water Crumbling Paper Def: a change that produces one or more new substances A chemical reaction will take place Burning paper Corrosion Rusting Milk or eggs going BAD

Nonmetals Lack the properties of metals Poor conductors of electricity and heat Reactive with other elements Dull and brittle (break easily) Good insulators

Metalloids & Noble Gases Metalloids has characteristics of both metals and nonmetals Semiconductors: substances that can conduct electricity under some conditions Unreactive elements Exist in Earth’s atmosphere