Structure of Atoms

Atom- Basic unit of matter Nucleus- center of the atom Proton- Positive Particle Neutron- Neutral Particle Electron - Negative Particle

Atomic number = number of protons Number of protons = number of electrons

Atomic Mass/Weight= Neutrons + Protons So… Neutrons = Atomic Mass – Atomic # Ex. 12.0115 – 6 = 6 neutrons You have to round the Atomic mass to the Nearest whole number

-Electrons orbit the nucleus -The first orbit holds two electrons -The second orbit holds eight electrons -The third orbit holds eight electrons

Electrons in the outer most orbital are called valence electrons

Compound- Substance formed by the chemical combination of two or more elements in definite proportions

Element A pure substance that consists entirely of one type of atom Ex- Hydrogen (all atoms have 1 electron) Calcium (all atoms have 20 electrons) Gold (all atoms have 79 electrons)

Chemical Bonds

Ion An atom that has a positive or negative charge How can this happen? What would have to change for an atom to become an ion?

Chemical Bonds Sodium Chlorine Table Metal Gas Salt 1. Ionic- bond formed when one or more electrons are transferred from one atom to another (two or more ions attracted to one another b/c of opposite charges)

Ionic Bond Properties Molecules with Ionic bonds have crystal lattice structures High melting and boiling points Tend to be brittle solids Are dissolved (soluble) in water Conduct electricity well

Covalent- bond formed when electrons are shared between atoms

Covalent Bond Properties Stronger than ionic bonds Often in gases, liquids, or soft solids Poor conductors of heat and electricity Low melting and boiling points

Metallic Bonding the covalent bonding between atoms in metals, in which the valence electrons are free to move through the crystal. Electrons are shared between atoms Very strong bonds Conduct heat and electricity well

Van der Waals Forces- slight attraction between nearby atoms

Chemical Reaction- changes one set of chemicals to another by changing bonds Reactant- elements or compounds going into reaction Product- elements or compounds coming out of reaction 2H2 + O2 → 2H20 H and O are reactants H2O is the product

Reactions can be Reversible CO2 + H2O H2CO3 H2CO3 CO2 + H2O How many atoms of oxygen are in the products of the second reaction? How many molecules of carbon are in the products of the first reaction?

Weekend Write #2 A. How is a car like a living organism? As Biologists, why do we consider a car to be nonliving? B. Explain how elements are different from compounds and give 2 examples of each.

Finished? Rewrite Weekend Write #1 Finish flashcards that were due today Study for quiz on Tuesday (scientific method, characteristics of life, chemistry) Read section 2-3 in the text book