Atoms and Elements

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Chemistry
Chapter 4
updated 6 years ago by chaneasegarvey
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1

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
2

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
3

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
4

Periodic Table

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  • organizes 118 elements into groups with similar properties
  • places them in order of increasing atomic mass
5

Periods (periodic table)

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  • horizontal rows of elements
  • counted from top to bottom of the table
  • Periods 1 to 7
6

Groups (periodic table)

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  • vertical columns
  • contains elements with similar properties
7

Group Number (periodic table)

  • written at the top of each vertical column
  • uses A for representative elements or B for transition elements
8

Representative Elements (periodic table)

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  • uses the letter A
  • (Groups 1A - 8A)
9

Transition Elements (periodic table)

  • uses the letter B
  • in center of periodic table
  • (Groups 3B - 12B)
10

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)
11

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
12

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
13

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
14

Metals Nonmetals, and Metalloids

  • separated by heavy zigzag line
  • metals... to the left
  • nonmetals... to the right
  • metalloids... along the heavy zigzag line
15

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
16

Nonmetals

  • located to the right of zigzag
  • dull
  • brittle
  • poor conductors of heat and electricity
  • low densities
  • low melting points
17

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
18

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
19

Atom

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  • 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
20

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
21

Electrical Charges in an Atom

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  • 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
22

Determination of the Mass of an Atom

  • The masses of the protons and neutrons in the nucleus determine the mass of an atom
23

Atomic Mass Unit

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  • 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
24

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
25

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
26

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
27

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
28

Atomic symbol

  • The mass number in the upper left corner
  • The atomic number in the lower left corner
29

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
30

Energy Levels

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  • 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
31

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
32

Electron Arrangement

  • Gives the number of electrons in each and Energy level
33

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
34

Electron dot symbol

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  • Also known as Lewis structures
  • Represents the valance electrons as dots place on the sides of a symbol
35

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