Chemistry Notes Atom 1)_____ : basic unit of matter a) nm Roughly 0.2 ___ in diameter b) Composed of: protons (+), neutrons ( 0 ), electrons ( - )
Chemistry Notesc) Protons and neutrons are found in nucleus the ______ of the atom i. The number of protons (and electrons) in an atom is determined by the atomic ________ number. ii. The number of neutrons is determined by subtracting the ___________ from Atomic number the ___________. Atomic mass Atomic mass – atomic number = neutron #
Chemistry Notesa.Why do we subtract?An atom’s mass is made up of only protons and neutrons because the mass of an electron is negligible (1/1840 mass of a proton)
Chemistry Notes Atomic mass Atomic number Element SymbolElement Name
Chemistry Notesd) orbit Electrons _________ around the nucleus in energy levels, or ____________ Shells i. These shells represent the most probable place that an electron can be found at any one time. ii. Each shell holds a different number _________ of electrons.
Chemistry Notesiv. To properly place an atom’s electrons in the orbitals, follow these guidelines: 1) Start with the innermost orbital and draw two electrons 2) If you have electrons left, move to the next orbital and draw up to eight electrons; continue filling up the orbital until you run out of electrons.
v. This * orbital actually holds more than what is listed. You will learn more about this in Chemistry!vi. The electrons in the outermost shell of an atom are so important that they valence have a special name -__________ electrons
Chemistry Notes2)Element: pure substance made of one ______ type of atom a. Grain of Sand (Atom) vs. Beach (Element) b. Periodic Table of Elements c. Six most important elements for living things: C,H,O,N,P,S
Chemistry Notes3) Isotope: ______ element, same different number of ________. neutrons
Chemistry Notesb) properties Same chemical _____________ due electrons to same number of _____________.c) Radioactive isotopes: nuclei unstable __________ and breaks down at a constant rate.
Chemistry Notes Carbon-14 Datingd) ____________________ can be used to determine the age of biological artifacts up to 50,000 years old by the ratio of radioactive carbon-14 to nonradioactive carbon-12 in the artifact.
Chemistry Notes4) Compound: Two or more definite elements in ________ proportions. a) formula Has a chemical ________. ex. H2O, NaCl, C6H12O6 b) Compounds are different than the elements that make them up
Chemistry Notesi. Ex: Sodium (Na) explodes in cold water, chlorine (Cl) is a poisonous gas. NaCl is ______. salt + =
Chemistry Notesii. Oxygen (O2) and Hydrogen (H2) individually are gases, but together they are a liquid (H2O)!! + =
Chemistry Notes5) Chemical Bonds Hold atoms in _____________: compounds together a) Ionic Bond: Forms when valence electron (s) move from one atom to _____ another atom. i. Ionic bonds occur between metals nonmetals and ____________.
Chemistry Notesii. Why do electrons what to move in the first place? 1) stable Atoms want to be _______ by having a full ______ outer ring. Most are NOT stable by themselves. This oxygen atom is NOT stable.
Chemistry Notes2) To become stable, an atom reacts with other atoms by giving up or gaining electrons in order to end up eight with _______ valence electrons Two (_____ for the first orbital), This is octet called the_______ rule.
Chemistry Notesiii. An atom that has gained or lost electrons is called an ion _________. (1)Atoms that give up electrons become __________ positively charged. (2)Atoms that gain electrons become __________ negatively charged.
Chemistry Notesiv. Some atoms already have a full outer orbital by themselves. a) Which of the atoms that you drew earlier fits this description? _________ argon b) These atoms are known as the _____________ noble gases (Group 18)
Chemistry Notesv. Ionic Bond Examples: 1. NaCl Salt 2. Fe2O3 Rust
Chemistry Notesb) Covalent Bonds: _______ electrons Shared between atoms i. Moving electrons spend time between ______ atoms both ii. Occurs between nonmetals and nonmetals _________. iii. Atoms achieve their full outer shell status by sharing electrons
Covalent Bondsiv. Electron sharing combinations single 1) Two electrons shared = ______ bond 2) Four electrons shared = double bond Six 3) _______ electrons shared = triple bond
Chemistry Notesv. Molecules __________ form when atoms join covalently Use your brain power: Decide which picture accurately depicts the relationship between compounds and molecules
Chemistry Notes6) Van der Waals Forces: When the sharing of electrons is ______ and a molecule has unequal regions that are charged. a) Weaker than ionic or covalent bonds b) Geckos stay on walls because of these forces