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Elements, Atoms, and Molecules

Elements, Atoms, and Molecules. Mrs. Dennis Commonwealth Governor’s School. Chemistry and Living Things. Bombardier Video. http:// www.youtube.com/watch?v=j-wVFLucTks&feature=related. Matter. All living things are composed of matter . Matter is anything that occupies space and has mass.

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Elements, Atoms, and Molecules

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  1. Elements, Atoms, and Molecules Mrs. Dennis Commonwealth Governor’s School

  2. Chemistry and Living Things

  3. Bombardier Video • http://www.youtube.com/watch?v=j-wVFLucTks&feature=related

  4. Matter • All living things are composed of matter. • Matter is anything that occupies space and has mass. • Examples: rocks, water, gases and living organisms.

  5. Matter is composed of Elements • An element is a substance that cannot be broken down to other substances by ordinary chemical means.

  6. Living Organisms are composed of about 25 elements • Chemicals are at the base level of biological hierarchy • They are arranged into higher and higher levels of structural organization. • Arrangement eventually leads to formation of living organisms

  7. Some trace elements are required to prevent disease • Without iron (Fe), your body cannot transport oxygen • An iodine deficiency (I) prevents production of thyroid hormones, resulting in goiter.

  8. Trace elements are common additives to food and water • Chemicals can be added to food for a variety of reasons. • Help preserve it • Make it more nutritious • Make it look better

  9. ELEMENTS COMBINE TO FORM COMPOUNDS • A compound is a substance consisting of two or more different elements combined in a fixed ratio. • Compounds are much more common than pure elements.

  10. Many compounds consist of only two elements. Example: sodium chloride (NaCl) This is a crystalline compound formed by equal numbers of sodium ions (Na+) and chloride ions (Cl-)

  11. 2Na (s) + Cl2 (g) 2NaCl (s)

  12. Compounds have different properties than the elements that make them up.

  13. Most Important Compound to Living Things • Water (H2O) • Hydrogen (H2) and Oxygen (O2) both are gases in their pure elemental form. In the right mixture (not chemically combined), they are explosive. • In a 2:1 ratio of H atoms to O atoms in a compound (chemically combined) the substance is a liquid.

  14. Many of the compounds in living organisms contain carbon, hydrogen, oxygen, and nitrogen. • DNA, for example, contains all four of these elements • Interestingly, different arrangements of elements provide unique properties for each compound.

  15. CHNOPS • Carbon – building blocks of large organic molecules. • Hydrogen – also part of building blocks and a component of water • Nitrogen – a component of amino acids that make up proteins.

  16. CHNOPS (cont’d) • Oxygen – important in cellular respiration. • Phosphorous – very important in holding together DNA and is in the major energy molecule adenosine triphosphate (ATP). • Sulfur – important in giving proteins structure.

  17. Atoms • An atom is the smallest unit of matter that still retains the properties of a element • Atoms are made of many subatomic particles, but only three are important for biological compounds

  18. Atoms consist of protons, neutrons, and electrons • Proton (p+) —has a single positive electrical charge. • Electron (e-)—has a single negative electrical charge. • Neutron (n0)—is electrically neutral.

  19. Protons and neutrons are located in the atom’s nucleus. • Electrons are located in orbitals (3-D spaces) that form an electron cloud around the nucleus. • ELECTRONS GIVE ATOMS OF AN ELEMENT THEIR PROPERTIES.

  20. Elements differ in their number of protons, neutrons, and electrons

  21. Hydrogen

  22. Helium

  23. Carbon

  24. Carbon 6 electrons in the electron cloud

  25. ISOTOPES • Although all atoms of an element have the same atomic number, some differ in mass number. • The variations are isotopes, which have the same numbers of protons and electrons but different numbers of neutrons. • One isotope of carbon has 8 neutrons instead of 6 (written 14C) or C-14 • Unlike 12C, 14C is an unstable (radioactive) isotope that gives off energy

  26. Isotopes of Carbon

  27. Periodic Table • The elements in the periodic table are arranged in increasing atomic number, therefore increasing number of electrons. • Elements in a group (column) all have the same number of outer electrons which are also called “valence electrons.”

  28. Electron arrangement determines the chemical properties of an atom. • Only electrons are involved in chemical activity. • Electrons occur in energy levels called electron shells.

  29. An atom may have one or more electron shells. • The number of electrons in the outermost shell determines the chemical properties of the atom. • The first shell is full with two electrons, whereas the second and third will hold up to eight electrons each.

  30. Chemical Bonds • When two atoms with incomplete outer shells react, each atom either shares, donates, or receives outer electrons, so that both partners end up with completed outer shells. • These interactions usually result in atoms staying close together, held by attractions known as chemical bonds.

  31. Three Important Types of Bonds • Ionic • Covalent • Hydrogen Bonding

  32. IONIC BONDS • Actually transfer electrons. • The atom that loses an electron and becomes positively charged ion is called a cation. • The atom that gains an electron and becomes a negatively charged ion is called an anion.

  33. Ions • Ion – an atom or molecule with an electrical charge resulting from a gain or loss of one or more electrons.

  34. Ionic Bonds • Two ions with opposite charges attract each other; when the attraction holds them together, it is called an ionic bond.

  35. Formation of an ionic bond, producing sodium chloride

  36. sodium chloride crystal

  37. Dissolving • There is a very strong attraction between the oppositely charged ions but if we add to water the salt will dissolve, that is the ions break apart and become surrounded by water molecules.

  38. IONIC BONDS http://www.youtube.com/watch?v=xTx_DWboEVs&feature=related

  39. COVALENT BONDS • When two atoms share valence electrons resulting in both atoms having a filled outer level. • Single Bond: 2 electrons are shared. • Double Bond: 4 electrons are shared. • Triple Bond: 6 electrons are shared.

  40. Nonpolar vs. Polar Bonds between Atoms • Depends on the electronegativity of the each of the bonding atoms. • Electronegativity is a measure of how closely an atom of a element will pull the shared pair of electrons towards its nucleus.

  41. Nonpolar covalent bond • the bonding pair of electrons will be shared equally between the two bonding atoms. • Polar covalent bond • The bonding pair of electrons will spend more time closer to the more electronegative atom’s nucleus. • Example: The bonds between H and O in a H2O molecule

  42. Covalent bonds are usually formed by two nonmetals.

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