Protons, Electrons, and Neutrons

Charges:  Electrons - Negatively charged  Protons - Positively charged  Neutrons – Neutral (no charge)

Be 9.01 Beryllium 4 Element Name Atomic Number Element Symbol Atomic Mass (# of protons and electrons) (# protons + # neutrons) protons) Mass Number - Atomic Number = # of neutrons = 5 (# protons)

Cl Chlorine P = E = N = What are the numbers of protons, electrons and neutrons? Protons = Electrons = Neutrons = 17 18

Where are protons, electrons, and neutrons located? Protons –inside the atomic nucleus Neutrons –inside the atomic nucleus Electrons –orbit the atomic nucleus Electrons Protons and Neutrons

Isotopes  Different atoms of the same element # Protons stays the same # Protons stays the same # Neutrons are different # Neutrons are different Ex. Carbon 12 – 6P, 6N, 6E Carbon 13 – 6P, 7N, 6E Carbon 13 – 6P, 7N, 6E Carbon 14 – 6P, 8N, 6E Carbon 14 – 6P, 8N, 6E The have the same # electrons  The chemical properties don’t change

Chemical Bonds 1. Ionic Bonds –formed b/w oppositely charged ions An atom that loses electrons has a + charge An atom that loses electrons has a + charge An atom that gains electrons has a – charge An atom that gains electrons has a – charge Ions- Positively and negatively charged atoms Ions- Positively and negatively charged atoms 2. Covalent Bonds- electrons are shared b/w atoms When atoms share 2 electrons => single covalent bond When atoms share 4 electrons => double covalent bond

Water and pH

Water  Covers 3/4 of Earth's surface  The single most abundant compound in most living things  One of the few compounds that is a liquid at the temperatures found on the Earth's surface

Density of Water  Unlike most substances, water expands as it freezes Ice is less dense than liquid water and therefore floats Ice is less dense than liquid water and therefore floats  If ice sank it would be disastrous for: 1.fish and plant life in regions w/ cold winters 2.sport of ice skating

Polarity: The Water Molecule  Water is a polar molecule Due to the unequal sharing of electrons Due to the unequal sharing of electrons The oxygen end has a slight (-) chargeThe oxygen end has a slight (-) charge The hydrogen end has a slight (+) chargeThe hydrogen end has a slight (+) charge edu/biology/Biology1111/animati ons/hydrogenbonds.htmlhttp://programs.northlandcollege. edu/biology/Biology1111/animati ons/hydrogenbonds.htmlhttp://programs.northlandcollege. edu/biology/Biology1111/animati ons/hydrogenbonds.htmlhttp://programs.northlandcollege. edu/biology/Biology1111/animati ons/hydrogenbonds.html + -

Hydrogen Bonds  Polar molecules, such as H 2 0, attract each other because of their partial (+) and partial (-) charges  This is a hydrogen bond  Not as strong as covalent or ionic bonds Because it is only b/w partial charges Because it is only b/w partial charges

Properties of Water  The ability of water to form multiple hydrogen bonds is responsible for many of water's properties One water molecule may be involved in 4 hydrogen bonds at the same time One water molecule may be involved in 4 hydrogen bonds at the same time

Properties of Water 1. Cohesion- an attraction b/w molecules of the same substance Why drops of water form beads on a smooth surface Why drops of water form beads on a smooth surface Also explains why some insects and spiders can walk on a pond's surface Also explains why some insects and spiders can walk on a pond's surface AKA “Surface Tension”AKA “Surface Tension”

Properties of Water (Cont’d) 2. Adhesion- an attraction b/w molecules of different substances The meniscus in a graduated cylinder The meniscus in a graduated cylinder Forms because adhesion b/w water molecules and glass molecules is stronger than the cohesion between water moleculesForms because adhesion b/w water molecules and glass molecules is stronger than the cohesion between water molecules Capillary Action Capillary Action Adhesion also causes water to rise in a narrow tube against the force of gravityAdhesion also causes water to rise in a narrow tube against the force of gravity One of the forces that draw water out of the roots of a plant and up into its stems and leavesOne of the forces that draw water out of the roots of a plant and up into its stems and leaves

Mixtures  Mixture- a material composed of 2+ elements or compounds that are physically mixed together but not chemically combined Examples - Salt & pepper or a Salad Examples - Salt & pepper or a Salad Cookies and Cream Ice Cream Cookies and Cream Ice Cream

Solutions  Solution - Mixture of 2+ substances where the molecules of the substances are evenly distributed Solute - substance that is dissolved (ex. salt) Solute - substance that is dissolved (ex. salt) Solvent - substance in which the solute dissolves (ex. water) Solvent - substance in which the solute dissolves (ex. water) **Water is the universal solvent because of its polarity

pH Scale  A water molecule can react to form ions  The pH scale is used to indicate the concentration of H+ ions in solution  pH stands for “power of Hydrogen”

O H OH - If more H + than OH-, the chemical is an ACID If less H + than OH-, the chemical is a BASE If equal amounts of H + and OH-, the chemical is NEUTRAL O H OH - O H H+H+H+H+ H+H+H+H+ H+H+H+H+

More Acidic H + More Basic OH- Neutral 6 Litmus paper is used as an indicator for acids and bases Acids turn blue litmus  to red Bases turn red litmus  to blue An acid with a pH of 1 is stronger than one with a pH of 6 A base with a pH of 14 is stronger than a base with a pH of 8