Chemistry Chapter 8 Notes #1 Ions

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)

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)

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)

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

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 don’t pair up until they have to (Hund’s rule) X

Electron Dot diagrams … l Nitrogen has 5 valence electrons to show. l First we write the symbol. N l Then add 1 electron at a time to each side. l Now they are forced to pair up. l We have now written the electron dot diagram for Nitrogen.

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

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

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

Cations  calcium has only 2 valence electrons It’s easier to lose 2 than gain 6 Ca +2

Cations  Example Magnesium = 1s 2 2s 2 2p 6 3s 2 Mg +2 = 1s 2 2s 2 2p 6 Neon = 1s 2 2s 2 2p 6 Drawings

cations

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+

Anions  Nonmetals will have many valence electrons (usually 5 or more)  They will gain electrons to fill outer shell. P P 3- This is called the phosphide ion

Electron Configurations for Anions  Example Oxygen = 1s 2 2s 2 2p 4 O -2 = 1s 2 2s 2 2p 6 Neon = 1s 2 2s 2 2p 6  Drawings Oxygen

Ions

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