Chapter 6.1 Basic Chem

Atoms Atoms are the building blocks of matter Three basic sub-atomic particles PROTONS: positively charge; located in the nucleus NEUTRONS: neutral; located in the nucleus ELECTRONS: negatively charged; located outside nucleus

Atoms cont. Atomic structure is a result of the attraction between protons and electrons

Atomic Structure Protons and neutrons are contained inside the nucleus Protons are represented by atomic number Number of neutrons can be predicted by subtracting the atomic mass from the atomic number and rounding to the nearest whole. Number of electrons in a neutral atom should equal the number of protons

Oxygen Second energy level Protons (+ charge) Nucleus First energy level Electrons Neutrons (no charge)

Elements Pure substances that cannot be broken down into other substances Organized by characteristics on the Periodic Table

Isotopes Proton number (atomic number) is equal to the number of electrons, but NEUTRON number can vary. Atoms of the same element with different neutron numbers are called isotopes. Changing neutron number can make the atom unstable and cause it to decay. When this happens, the isotope gives off radiation

Compounds A substance formed from two or more elements bonded in a specific ratio Ex: CO2, NAOH, H2O, H2O2 Cannot be broken down into smaller parts physically; i.e. cannot be individually crushed or torn Can be broken down chemically

Atomic Structure and Octet Rule Electrons travel outside the nucleus in energy levels The first level holds up to two electrons The second holds up to 8 electrons The third holds up to 18 Full energy levels are more stable than partially filled ones Bonds are formed between atoms with unfilled energy levels because unstable atoms tend to bond

Chemical Bonds Ionic Covalent A bond formed when one atom donates one or more electrons to another atom. Both atoms become charged and are called “ions” The electrical charges of the atoms attract them to eachother A bond where a molecule is formed by two or more atoms SHARING electrons Covalent bonds can be single, double, or triple bond depending on how many electrons are shared

Covalent Bonds Two atoms will share one, two, or three electrons. The electrons travel between the electrons shells of both atoms. These electrons are shared

Ionic Bonds The atom with fewer electrons will donate to the atom with more electrons. The atom that receives the electrons becomes negatively charged The atom that donates the electrons becomes positively charged The two atoms are attracted to each other, like magnets

van der Waals Forces Electrons travel around the nucleus inconsistently. This leads to temporary positive or negative areas. When molecules come close together, these temporary positive and negative areas are attracted to each other This causes molecules to be attracted to each other. This attraction is known as van der Waals forces. In water, this causes cohesion, which is the reason water beads together.