CHAPTER 4 ATOMIC STRUCTURE

1
CHAPTER 4 ATOMIC STRUCTURE
2

• Aristotle (Greek)
• Thought all substances were built from either
  fire, earth, air, water
• Thought that atoms of a liquid are smooth and
  round
• Thought atoms of a solid were rough and prickly

3

• Daltons Atomic Theory (1766)
• Evidence for atoms
• Measured the masses of elements
• Compounds have fixed composition
• All matter is made up of individual particles
  called atoms, which cannot be divided

4

• 1 All elements are composed of atoms
• 2 All atoms of the same element have the same
  mass, and atoms of different elements have
  different masses
• 3 compounds contain atoms of more than 1 element
• 4 in a particular compound, atoms of different
  elements always combine the same way

5

• Evidence for subatomic particles
• Mass and charge are spread throughout the atom
• Earnest Rutherford- (1871-1937)
• Alpha particles---fast moving positive charged
• All the atoms positive charge is in the nucleus
• The nucleus is the positively charged mass
  located in the center of the atom
• Ques.1-5 pg. 105

6
SECTION 4-2

• Properties of subatomic particles
• Protons-- charged particles, varies among
  elements
• Each nucleus contains at least one positively
  charged particle
• charge proton

7

• Electron
• - charge 1-
• Found outside the nucleus in an electron cloud or
  (shell)

8

• Neutron
• No charge
• Found in the nucleus
• Mass almost to a proton
• Protons, electrons and neutrons can be
  distinguished by mass, location in an atom and
  the charge

9
ATOMIC NUMBER AD MASS NUMBER

• The atoms of any element contain the same number
  of protons
• Example there is one proton in the nucleus of
  every hydrogen atom. There hydrogen has an
  atomic number of 1
• ATOMIC NUMBER NUMBER OF PROTONS

10

• Atoms of different elements have different
  numbers of protons
• Sulfur atomic 16 because it has 16 protons in
  the nucleus
• Each positive charge is balanced by a negative
  charge SO hydrogen has 1 proton and 1 electron
  sulfur 16 protons and 16 electrons

11

• MASS NUMBER the sum of the protons and neutrons
  in the nucleus of the atom
• Ex Aluminum 13 protons14 neutrons an atomic
  mass of 27
• Number of neutrons mass-atomic number
• Ex. Aluminum 27-13 14 (of neutrons)

12
ISOTOPES

• When an atom does not have the same number of
  neutrons
• Same atomic number but different mass s
• Ex. Oxygen-16, 17, and 18
• All oxygen atoms have 8 protons, but some have 9
  or 10 neutrons
• Ques. 1-7 pg. 112

13

• Energy levels
• 1 one orbital max 2 electrons
• 2 four orbitals max 8 electrons
• 3 nine orbitals max 18 electrons
• 4 sixteen orbitals max 32 electrons

14

• Electron configurationarraignment of electrons
  in the orbitals of an atom
• Lowest levels get filled before higher energy
  levels----inner to outer
• Stable electron configuration is the one in which
  the electrons are in orbitals with the lowest
  possible energies (ground state)
• Ques. 1-5 pg. 118

15
4-3 Modern Atomic Theory

• Niels Bohr-1885-1962 Danish physicist focused on
  electrons in the electron cloud
• Energy levels
• Each electron has a fixed amount of energy
• Electrons closer to the nucleus have less energy
  than further away from the nucleus

16

• They move in a less than predicable way
• Atomic orbitals
• The electron cloud represents all the orbitals in
  an atom
• An orbital is a region of space around the
  nucleus figure 15 page 117 (copy into notes)
• Draw in your notes the Thomson, Rutherford, Bohr,
  and electron cloud models (pg 115)

17

• An electron in an atom can move between energy
  levels when the atoms gain or lose energy
• The size of the jump between orbitals determines
  the amount of energy gained or lost

18

• Evidence for movement from one level to another
  is light---light is a form of energy-----heat is
  another cause of movement of electrons from one
  orbital to another
• Electron cloud-how electrons behave in their
  orbitals
• Electrons move like planets in the solar system
  around the nucleus, they move in a less than
  predicable way

19

• When electrons move to a higher energy level they
  are considered in an excited state
• Ex. He, Ne, Ar Kr, Xe find out the names of
  these elements
• Page 118 questions 1-5

20
(No Transcript)