Elements

• pure substances from which all things are built
• cannot be broken down into simpler substances
• certain elements look alike and behave in the same way

Chemical Symbols

• one or two letter abbreviations for the names of the elements
• only the first letter is capitalized
• if two letters are capitalized... represents the symbols of two different elements

Mercury (Hg)

• a silvery, shiny element
• liquid at room temperature
• can enter the body:
  • inhaled mercury vapor
  • contact with the skin
  • ingestion of foods and water contaminated with mercury
• effect on body:
  • destroys proteins and disrupts cell function
  • can damage the brain and kidneys
  • can cause mental retardation
  • can decrease physical development

Periodic Table

• organizes 118 elements into groups with similar properties
• places them in order of increasing atomic mass

Periods (periodic table)

• horizontal rows of elements
• counted from top to bottom of the table
• Periods 1 to 7

Groups (periodic table)

• vertical columns
• contains elements with similar properties

Group Number (periodic table)

• written at the top of each vertical column
• uses A for representative elements or B for transition elements

Representative Elements (periodic table)

• uses the letter A
• (Groups 1A - 8A)

Transition Elements (periodic table)

• uses the letter B
• in center of periodic table
• (Groups 3B - 12B)

Alkali Metals (Group 1A)

• elements are:
  • soft
  • shiny
  • good conductors of heat and electricity
  • have relatively low melting points
  • react vigorously with water
  • form white products when they combine with oxygen
• includes:
  
  • Li (Lithium)
  • Na (Sodium)
  • K (Potassium)
  • Rb (Rubidium)
  • Cs (Cesium)
  • Fr (Francium)

Alkaline Earth Metals (Group 2A)

• includes:
  • Be (Beryllium)
  • Mg (Magnesium)
  • Ca (Calcium)
  • Sr (Strontium)
  • Ba (Barium)
  • Ra (Radium)
• elements are:
  • shiny
  • not as reactive as alkali metals

Halogens (Group 7A)

• includes:
  • F (Fluorine)
  • Cl (Chlorine)
  • Br (Bromine)
  • I (Iodine)
  • At (Astatine)
• elements are:
  • highly reactive
  • form compounds with most of the elements

Noble Gases (Group 8A)

• includes:
  • He (Helium)
  • Ne (Neon)
  • Ar (Argon)
  • Kr (Krypton)
  • Xe (Xenon)
  • Rn (Radon)
• elements are:
  • quite unreactive
  • seldom found in combination with other elements

Metals Nonmetals, and Metalloids

• separated by heavy zigzag line
• metals... to the left
• nonmetals... to the right
• metalloids... along the heavy zigzag line

Metals

• located to the left of zigzag
• shiny solids
• can be shaped into wires (ductile)
• can be hammered into a flat sheet (malleable)
• good conductors of heat
• substances that loses electrons very easily
• usually melt at higher temperatures than nonmetals
• all metals are solids at room temperature except mercury

Nonmetals

• located to the right of zigzag
• dull
• brittle
• poor conductors of heat and electricity
• low densities
• low melting points

Metalloids

• located along zigzag
• better conductors than nonmetals but not as good as metals
• semiconductors, because they can be modified to function as conductors or insulators

Elements Essential to Health

• 20 elements essential for the well-being and survival of the human body
• Four elements -- Oxygen, carbon, hydrogen, and nitrogen make up 96% of our body mass
• Macro minerals-- Ca, P, K, CL, S, Na, and Mg
  • are representative elements involved in the formation of bones and teeth, maintenance of heart and blood vessels, muscle contractions, nerve impulses, acid-base balance of bodily fluids
  • Regulation of cellular metabolism

Atom

• all elements on the periodic table are made up of atoms
• the smallest particle of an element that retains the characteristics of that element
• consists of a nucleus that contains protons and neutron
• Electrons are in a large empty space around the nucleus
• Protons are inside the nucleus
• Neutrons are also inside the nucleus

Dalton's Atomic Theory

1. All matter is made up of tiny particles call atoms
2. All atoms of a given element are similar to one another and different from atoms of other elements
3. Atoms of two or more different elements combine to form compounds
4. A chemical reaction involves the rearrangement, separation, or combination of the atoms. Atoms are never created or destroyed during a chemical reaction

Electrical Charges in an Atom

• Atoms contain subatomic particles:
  • Protons
    • have a positive charge
    • Much heavier than the electrons
    • Inside of the nucleus
    • Is attracted to an electron
    • one proton has a mass of 1.67 x 10^-24 g
  • Electrons
    • have a negative charge
    • much smaller than the atom
    • have extremely small masses
    • In a large empty space around the nucleus
    • Repel each other
    • one electron has a mass of 9.11 x 10^-28g
  • Neutrons
    • are neutral
    • Inside the nucleus

Determination of the Mass of an Atom

• The masses of the protons and neutrons in the nucleus determine the mass of an atom

Atomic Mass Unit

• ¹/₁₂th of the mass of a carbon atom which has a nucleus contains six protons and six neutrons
• A proton has a mass of about 1 (1.007) amu
• A neutron has mass of about 1 (1.008) amu
• An electron has a very small mass, 0.000549 amu

Atomic number

• is a whole number specific for each element
• Is the same for all atoms of an element
• Is equal to the number of protons in and atom
• appears above the symbol of an element in the periodic table
• The number of electrons is also equal to the atomic number

Atom is electrically neutral

• The number of protons in and atom is equal to the number of electrons which gives every Adam and overall charge of zero

Mass Number

• Is the total number of protons and neutrons in the nucleus
• Does not appear on the periodic table
• Mass number = number of protons + number of neutrons
• represents the number of particles in the nucleus
• Always a whole number

Isotopes

• atoms of the same element that have the same atomic number but different numbers of neutrons
• Have the same number of protons but different numbers of neutrons
• Can be distinguished by their atomic symbols

Atomic symbol

• The mass number in the upper left corner
• The atomic number in the lower left corner

Atomic Mass

• A weighted average of all the naturally occurring isotopes of an element
• the number including decimals that is given below the symbol of each element

Energy Levels

• Assigned principal quantum numbers
• Electrons in the lower energy levels are closer to the nucleus
• While electrons in the higher energy levels are farther away from the nucleus
• The energy of an electron is quantized… It can only have specific energy values
• All the electrons of the same energy are grouped in the same energy level
• The higher energy levels are closer together
• The lower electron energy levels hold fewer electrons in a higher energy levels

Changes in electron energy level

• Electrons move to higher energy levels when they absorb energy
• When electrons fall back to lower energy level, light is emitted
• the energy emitted or absorbed is equal to the differences between the two energy levels

Electron Arrangement

• Gives the number of electrons in each and Energy level

Valence Electrons

• The number electrons in the outermost energy level
• The group number gives the number of valance electrons for each of the representative elements

Electron dot symbol

• Also known as Lewis structures
• Represents the valance electrons as dots place on the sides of a symbol

Atomic size

• Is determined by the atom's atomic radius, the distance between the nucleus and outermost electrons
• Increases for representative elements from top to bottom of the periodic table
• Decreases with within a period As a result of the increased number of protons in the nucleus