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Chemistry Basics

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Chemistry Basics

  1. 1. Chemistry Basics Science is Organized Knowledge
  2. 2. What is "Stuff" Made of?• Anything that occupies space and has mass is matter. – Matter is all the “stuff” in the physical universe – All matter is made of atoms joined together.• Matter can assume different forms: – B.E. Condensate – Solid: definite shape and volume – Liquid: changeable shape, definite volume – Gas: changeable shape and volume – Plasma• Mass is a measurement of how much matter an object contains – weight • measures gravitys pull on the atoms in the matter of an object – density • measures how tightly packed together the atoms of an object are – volume • is a measurement of how much space the atoms of an object takes up
  3. 3. Elemental Chemistry• An element is the simplest form of matter – each element has unique chemical properties • how they interact with other atoms – some elements share physical properties • measurable or detectable with our senses • (what it looks or smells like, its dense, etc.) – comprised of a single type of atom
  4. 4. The Atom• Atoms are the building blocks of matter – 100 trillion atoms can fit on the head of a pin• Atoms join together (bond) to form elements • The different parts of an atom are called subatomic particles: – electrons • negative (-) charge – protons • positive (+) charge – neutrons • no charge (neutral)
  5. 5. Atomic Structure electron shell aka orbitalproton aka energy level nucleus N + - N + -electron neutron HELIUM ATOM
  6. 6. Elements & Compounds• Each element is made up of only ONE kind of atom. – elements defined by # of protons (atomic number) – named for their properties or after scientists (or their countries) – sorted into a chart (listed by atomic # and grouped by energy levels)• When different atoms join together, a compound is formed. – Chlorine gas vs. Sodium chloride – Hydrogen gas and pure Oxygen vs. Water
  7. 7. Periodic Table Entries2 Atomic number # of protons in the nucleus 80He4.003 Atomic mass combined number of protons Hg 200.59 and neutrons in the nucleus (in atomic mass units) number of electrons = number of protons
  8. 8. Isotopes• An atom with more or fewer neutrons than protons is an isotope – doesnt change the electrical charge – does influence the atomic mass• Isotopes retain the same basic properties as the parent element
  9. 9. Electron Shells (a.k.a. orbitals) Electrons are arranged in energy levels valence or shells around the nucleus of an atom. electrons 18 34Ar39.948 Se 78.96• the inner shell holds a maximum of 2 electrons valence electrons• second shell holds a maximum of 8 electrons• third shell holds a maximum of 18 electrons• e-s in outer-most shell called valence electrons
  10. 10. Electron Cloud Theory• Unlike the planetary model, electrons do not stay in a neat, circular orbit around the nucleus.• Electrons actually spin so fast around the nucleus in different areas that its impossible to pinpoint their exact location. – like spinning fan blades look blurry – darker blue areas are locations where electrons are most likely to be found at any given moment
  11. 11. SecondOctet Rule = atoms tend to gain, lose or share electrons so as tohave filled energy levels (usually 8 electrons) C would like to Gain 4 electrons N would like to Gain 3 electrons O would like to Gain 2 electrons
  12. 12. Week 3 Lab Water & DiffusionEgg Permeability Experiment
  13. 13. Ions• Atoms lose or gain an electron to become electrically charged – loss of electron results in more protons than electrons (positive charge) – gained electron causes more electrons than protons (negative charge)• Usually, ions retain the same basic properties as the base element• Isoelectronic = having the same electron configuration
  14. 14. Chemical Bonding• Elements are attracted and “stick” to each other as they attempt to fill electron shells• A chemical reaction is when atoms interact, forming or breaking bonds – Two kinds of bonds we often see in Biology are: 1. Covalent bonds – electrons are shared 2. Ionic bonds – electrons are transferred
  15. 15. Ionic Bonds• Ionic bonds form between atoms with opposite charges – bond formed by the transfer of electrons – produce charged ions – Examples: NaCl, CaCl2 Calcium chloride Sodium chloride
  16. 16. Sodium (metal) + Chlorine (gas) = Table Salt?• One electron from Sodium (Na) is transferred to Chlorine (Cl).• This causes a charge imbalance in each atom as ions are formed.• The Na becomes (Na+) and the Cl becomes (Cl-).• Opposite charges of the ions cause an attraction that keeps them bonded together• So through ionic bonding, two elements (a HIGHLY reactive metal and a DEADLY poisonous gas) form a fairly stable compound that we eat all the time!
  17. 17. Sodium Chloride (Table Salt) Magnified Salt Crystals
  18. 18. Covalent Bonds• Covalent bonds form between elements of similar charges – formed by sharing electron pairs – Examples: CO2, O2, H2O Oxygen gas Lewis Dot Structures WaterCarbondioxide
  19. 19. Non-polar Covalent BondWith non-polar H2molecules, twoatoms shareone or more F2pairs of outer-shell electronsequally. CO2 CF4- small (subscript) number refers to # of atoms of PREVIOUS element in each molecule
  20. 20. Polar Covalent BondIn polar molecules, two atoms share one or more pairs of outer-shell (valence) electrons unequally.- water is a polar molecule because oxygen is more electronegative thanhydrogen, and therefore electrons are pulled closer to oxygen.
  21. 21. Electronegativity of Bonds• How badly an atom "wants" (attracts) an electron will determine the type of bond and resulting electronegativity (charge) of the resulting molecule. • Ionic bonds form when atoms so strongly want to gain and donate electrons, an actual transfer occurs. • Non-polar covalent bonds form when electrons are shared equally, so both atoms "want" those e-s to the same degree. • Polar covalent bonds form when one atom wants an electron more strongly than the other, but is still willing to share, so the shared electrons spend more time around one atom than the other.
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