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Atoms and the Periodic Table

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Title: Atoms and the Periodic Table


1
Atoms and the Periodic Table
  • Chapter 4

2
Atomic Structure
  • Atoms are the simplest unit of a substance that
    still maintain the properties of the substance.
  • John Dalton proposed that atoms could not be
    divided.
  • Dalton also stated that atoms of different
    elements could join to form compounds.

3
Parts of an Atom
  • Atoms are composed of subatomic particles.
  • Protons and neutrons are found in the nucleus of
    the atom.
  • Electrons are found in orbitals around the
    nucleus of the atom.

4
Protons
  • Protons have a positive charge.
  • Protons have the mass of one amu (atomic mass
    unit).
  • The number of protons in an atom is
    characteristic of that element.
  • Each element has different number of protons.

5
Neutrons
  • Neutrons have no charge.
  • Neutrons have the mass of one amu.
  • Neutrons add to the mass of an atom.
  • Atoms of the same element with different number
    of neutrons have different masses (isotopes).

6
Electrons
  • Electrons have a negative charge.
  • Electrons have the mass of 1/2000 the mass of a
    proton.
  • The mass of an electron is insignificant.
  • The outer most electrons determine how elements
    combined in chemical compounds.

7
Quarks
  • A quark (IPA /kw?rk/) is a generic type of
    physical particle that forms one of the two basic
    constituents of matter, the other being the
    lepton.
  • Various species of quarks combine in specific
    ways to form protons and neutrons, in each case
    taking exactly three quarks to make the composite
    particle in question.

8
Models of Atoms
  • Niels Bohr suggested that electrons in an atom
    move in set paths around the nucleus.
  • Electrons can only be in certain energy levels.
  • Number of electrons2n2

9
Electron Cloud Model
  • This model suggest that electrons orbit the
    nucleus in a cloud.
  • The regions in an atom where electrons are likely
    to be found are called orbitals.
  • The four different kinds of orbitals are the s,
    p, d and f orbitals.

10
Valence Electrons
  • An electron in the outermost energy level of an
    atom is called a valence electron.
  • Valence electrons determine an atoms chemical
    properties and its ability to form bonds.

11
Periodic Table
  • The Periodic Law states that when elements are
    arranged this way, similarities in their
    properties will occur in a regular pattern.

12
Structure of the Periodic Table
  • Horizontal rows in the periodic table are called
    periods.
  • Atoms of elements in the same group, or column,
    have the same number of valence electrons, so
    these elements have similar properties.

13
Ions Formation
  • Atoms that gain or lose electrons form ions.
  • Elements that lose electrons have a positive
    charge (cation).
  • Elements that gain electrons have a negative
    charge (anion).

14
Periodic Information
  • The atomic number is the number of protons in an
    element.
  • The mass number of an atom equals the number of
    protons plus the number of neutrons.

15
Isotopes
  • Isotopes are atoms of the same element that have
    different number of neutrons.
  • Isotopes of the same element have different
    atomic masses.
  • The three isotopes of hydrogen are protium,
    deuterium tritium.

16
Mass of Atoms
  • An atomic mass unit (amu) is equal to one-twelfth
    of the mass of a carbon 12 atom.
  • The average atomic mass for an element is a
    weighted average, so the more commonly found
    isotopes have a greater effect on the average
    than rare isotopes.

17
Squares on the Periodic Table
  • The chemical symbol is abbreviation of the
    chemical name.
  • The first letter of the chemical symbol is
    capitalized.
  • If there is more than one letter, the other
    letters are lower case.
  • Atomic number.
  • Average atomic mass.

18
Classifications of Elements
  • Metals are on the left side of the periodic
    table.
  • Nonmetals are on the right side of the periodic
    table.
  • Metalloids are located between the metals and
    nonmetals.

19
Alkali Metals
  • This is the most reactive group of metals.
  • Has only 1 valence electrons.
  • Reacts violently with water.
  • Elements include Li, Na, K, Rb, Cs Fr.

20
Alkaline Earth Metals
  • Not as reactive as Alkali Metals.
  • Has two valence electrons.
  • Members include Be, Mg, Ca, Sr, Ba Ra.

21
Transition Metals
  • Members have a wide variety of properties.
  • Has 1, 2 or 3 valence electrons.
  • Contain the coin metals gold, silver copper.
  • Contain the iron triad of Fe, Co Ni.

22
Halogens
  • The most reactive group of nonmetals.
  • Has 7 valence electrons.
  • All members are poisonous.
  • Members include F, Cl, Br, I At.

23
Noble Gases
  • Members contain a stable octet with 8 valence
    electrons.
  • These elements do not react with other elements.
    Dont form compounds.
  • Members include He, Ne, Ar, Kr, Xe Rn.

24
Semiconductors
  • Have the properties of both metals nonmetals.
  • Used in the electronic industry.

25
Using Moles to Count Atoms
  • A mole is a collection of a very large number of
    particles.
  • Avagadros constant is the number of particles in
    a mole of a pure substance.
  • Avagadros constant is 6.022 x 1023/mol.

26
Molar Mass
  • Molar mass is the mass in grams of 1 mol of a
    substance.
  • The molar mass of an element in grams is the same
    as its average atomic mass in amu on the periodic
    table.

27
Converting Moles to Grams
  • Amount(mol) x molar mass of element/1 mol of
    element mass(g)
  • Amount(mol)1 mole of element/molar mass of
    element x mass(g)

28
Converting Amount to Mass
  • Determine the mass in grams of 5.50 mol of iron.
  • Given amount of iron5.50 mol mol Fe
  • molar mass of iron55.85 g/mol Fe
  • Unknown mass of iron?g Fe
  • 55.85 g Fe/1 mol Fe
  • 5.50 mol Fe x 55.85 g Fe/1 mol Fe307 g Fe

29
Converting Mass to Amount
  • Determine the amount of iron present in 352 g of
    iron.
  • Given mass of iron352 g Fe
  • molar mass of iron55.85 g/mol Fe
  • Unknown amount of iron? mol Fe
  • 1 mol Fe/55.85 g Fe
  • 352 g Fe x 1 mol Fe/55.85 g Fe6.30 mol Fe

30
Sample Problem 1
  • A chemical reaction requires 5.00 mol of sulfur
    as a reactant. What is the mass of this sulfur
    in grams?
  • 160.4 g S

31
Sample Problem 2
  • For an experiment you have been asked to do, you
    need 1.5 g of iron. How many moles of iron do
    you need?
  • 0.027 mol Fe

32
Sample Problem 3
  • James is holding a balloon that contains 0.54 g
    of helium gas. What amount of helium is this?
  • 0.14 mol He

33
Sample Problem 4
  • A pure gold bar is made of 19.55 mol of gold.
    What is the mass of the bar in grams?
  • 3851 g Au

34
Sample Problem 5
  • Robyn recycled 15.1 mol of aluminum last month.
    What mass of aluminum in grams did she recycle?
  • 407 g Al
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