Presentation on theme: " What would you find in the nucleus of an atom? An electron has what charge? What is an element? Define matter: What does the atomic number correspond."— Presentation transcript:
What would you find in the nucleus of an atom? An electron has what charge? What is an element? Define matter: What does the atomic number correspond to? What makes up the atomic mass? What is a valence electron? What main types of bonds are there? What is the pH scale?
Atoms Atoms are the building blocks of all matter. “A-” means “cannot” & “-tomos” means “cut” Elements are types of matter that contain only one type of atom. –Examples of elements: hydrogen, carbon, and oxygen
The Structure of Atoms Atom are composed of a nucleus orbited by electrons. The nucleus contains protons and neutrons. Nucleus Electron Orbitals
SO…Protons & Electrons attract to one another - this keeps the electrons in orbit around the nucleus
Valence Electrons The last energy level holds the valence electrons. The column, or group, on the periodic table indicates the number of valence electrons an element contains. The number of valence electrons determines an atom’s bonding properties. –8 valence electrons = Noble Gases Lewis Dot Structures
Putting Elements Together If a sample of matter contains two or more elements chemically combined in a certain ratio, it is called a compound. –Examples: water (H 2 O), salt (NaCl), and glucose (sugar) C 6 H 12 O 6 Compounds have properties that are different from the elements it contains. Chemical Bonding Chemical bonding allows atoms and molecules to “stick” together.
Types of Chemical Bonding Covalent Bonding – Atoms share electrons. Ionic Bonding – Atoms gain or lose electrons to form charge particles called ions. Ions then bond together because opposite charges attract. Hydrogen Bonding – Molecules stick together because certain parts of them are charged. The oppositely charged parts stick together. STRONG WEAK
Molecule = covalent bonds Water molecules attract by hydrogen bonds
Ionic bonds form between metals and non-metals, In naming simple ionic compounds, the metal is always first, the non-metal second (ie. sodium chloride),ionic compounds Ionic compounds dissolve easily in water and other polar solvents,compounds In solution, ionic compounds easily conduct electricity,solutionionic compounds Ionic compounds tend to form crystalline solids with high melting temperatures.compounds Na Cl Na+ Cl- (salt)
Knowing about the structure of atoms can help us understand the functions of certain elements in living things.
Water Importance of water: 1.Water molecules are polar Electronegativity 2.Water molecules are cohesive Hydrogen bonds 3.Water has a high-temperature stabilizing capacity Common boiling points: Methanol 64.7 ºC Diethyl ether 35 ºC Water 100 ºC 4.Water is the universal solvent Spheres of hydration Hydrophobic vs. hydrophilic
What does pH measure? H 2 OH + + OH - water Hydrogen ion Hydroxide ion
pH Hydrogen ion (H + ) is the most reactive ion in nature pH scale is the measure of the concentration of H + ions in a solution
pH pH scale ranges from 0 to 14 pH of a solution decreases with acidity Each step on the pH scale represents a factor of 10 –A solution with a pH of 5 has 10 times more H + ions than a solution with a pH of 6
Acids and Bases An acid is any compound that forms H + ions when it is dissolved in water to form a solution below 7 –Acids have pH values below 7 A base is a compound that forms hydroxide ions (OH - ) in solution above 7 –Bases have pH values above 7