Chemistry

1
Chemistry

• Chapter 8
• Notes 1
• Ions

2
Compounds

• 2 or more elements combined
• Example Sodium Chlorine Sodium Chloride
  (which is table salt)
• A compounds properties are different from the
  properties of the individual elements that make
  it up
• Compounds can be represented by chemical formulas
• Ex. NaCl (salt)

3
Compounds

• Compounds are held together by chemical bonds
• Attractive forces that hold atoms or ions
  together
• Ionic (referred to as formula units)
• Metallic
• Covalent (referred to as molecules)

4
Valence Electrons

• The electrons responsible for the chemical
  properties of atoms, and are those in the outer
  energy level.
• Valence electrons - The s and p electrons in the
  outer energy level
• the highest occupied energy level
• Core electrons the inner electrons (those in the
  lesser energy levels)

5
Valence Electrons

• Atoms in the same column...
• Have the same outer electron configuration.
• Have the same valence electrons.
• The number of valence electrons are easily
  determined the group number for a representative
  element
• Group 2A Be, Mg, Ca, etc.
• have 2 valence electrons

6
Electron Dot diagrams

• A way of showing keeping track of valence
  electrons.
• How to write them?
• Write the symbol - it represents the nucleus and
  inner (core) electrons
• Put one dot for each valence electron (8 maximum)
• They dont pair up until they have to (Hunds
  rule)

X
7
Electron Dot diagrams

• Nitrogen has 5 valence electrons to show.
• First we write the symbol.

N

• Then add 1 electron at a time to each side.

• Now they are forced to pair up.
• We have now written the electron dot diagram for
  Nitrogen.

8
Stable Electron Configurations

• All atoms react to try and achieve a noble gas
  configuration.
• Noble gases have 2 s and 6 p electrons.
• 8 valence electrons already stable!
• This is the octet rule (8 in the outer level is
  particularly stable).

Ar
9
Ions

• Ions atoms that have lost or gained valence
  electrons, resulting in an overall charge
• They lose or gain to meet the octet rule
• Cations positive ions (loss of electrons)
• Metals form positive ions
• Anions negative ions (gain of electrons)
• Nonmetals form negative ions

10
Cations

• Form when metals lose electrons
• Trying to meet the octet rule-Achieve a noble gas
  configuration
• Ex. Sodium (Na) becomes Na
• Loses its 1s electron- Then has the same electron
  configuration as Neon

11
Cations

• calcium has only 2 valence electrons
• Its easier to lose 2 than gain 6

Ca
Ca
2
12
Cations

• Example
• Magnesium 1s22s22p63s2
• Mg2 1s22s22p6
• Neon 1s22s22p6
• Drawings

13
cations
14
Cations

• Transition Metals
• Most of the time will have a 2 or 3 charge
• They lose both electrons from their outermost s
  sublevel
• Then, they can also lose inner unpaired d
  sublevel e-
• Which leads to a charge of more than 2
• Pseudo noble gas configurations (Non octets with
  stability)
• Example A pseudo-noble gas configuration is
  1s2 2s2 2p6 3s2 3p6 3d10 (and they have 2 in 4s)
• This is found in Cu Zn2 Ga3 and Ge4

15
Anions

• Nonmetals will have many valence electrons
  (usually 5 or more)
• They will gain electrons to fill outer shell.

P3-
P
This is called the phosphide ion
16
Electron Configurations for Anions

• Example
• Oxygen 1s22s22p4
• O-2 1s22s22p6
• Neon 1s22s22p6
• Drawings

Oxygen
17
Ions
18
Polyatomic Ions

• Al individual elements that have lost or gained
  electrons are monatomic ions
• Binary compound 2 monatomic ions combine
• Oxidation Number the charge of the ion
• Polyatomic ions a group of more than 1 atom
  that loses and gains electrons
• They act like an individual ion
• Have one charge (as a unit)
• Oxyanions polyatomics with oxygen