chemical bonding atoms will bond together to become stable atoms may share electrons to become...
TRANSCRIPT
Chemical Bonding• Atoms will bond together to become stable
• Atoms may share electrons to become stable
-OR-• Atoms may gain or lose electrons to
become stable.
• By gaining or losing electrons these atoms can fill or empty their outer energy level
Ionic BondingIonic bond – bond between oppositely
charged ions, involving a total transfer of electrons between atoms
Ion – a charged particle
Types of Ions
Cations - lose electrons and become positively charged
Usually metals
Anions - gain electrons and become negatively charged
Usually non-metals
The Cation (+ ion) loses an electron(s) which is transferred to the Anion (- ion) so both become stable
The now oppositely charged ions are attracted to each other due to magnetism
• A neutral atom becomes an ion either by losing an electron (cation) or by gaining an electron (anion).
The transfer of the electron caused the
neutral sodium atom to become a positively
charged ion (a cation), and the neutral
chlorine atom to become a negatively charged
ion (an anion).
• When the transfer occurs, sodium’s valence shell is empty, making the next ring in the valence shell, which is full.
What is happening?• The one valence electron from potassium is transferred
to the iodine. Both become stable with now full outer rings. Potassium becomes positively charged (+1: lacking one electron) and Iodine becomes negatively charged (-1: one extra electron).
Multiple ions• The two valence electrons from magnesium are
transferred, one to each chlorine. All three become stable with now full outer rings. Magnesium becomes positively charged (+2: lacking two electrons) and each chlorine becomes negatively charged (-1: one extra electron).
Steps for Writing Ionic Formulas
1. Write the symbols for the ions with the cation first, and anion second.
2. Balance the charges by inserting subscripts. There must be equal numbers of positive and negative charges to balance out to zero overall charge.
3. Write the chemical formula, indicating with subscripts how many of each ion are needed to make a neutral compound.
Polyatomic Ions• Polyatomic ion – multiple atoms covalently
bonded together which, as a group, have an overall charge to become stable
• The group will lose or gain electrons to become stable.
• Act as a unit
• You cannot change subscripts of the polyatomic ion, but can have multiple of the unit.
• Examples: Hydroxide OH-
Sulfate SO42-
Phosphate PO43-
• This ion cannot be changed, but you can have more than one of the ion. Use parentheses and a subscript outside the parentheses to balance charges.
Beryllium chlorate
Be2+ ClO3-
Be2+(ClO3-)2
Multiple Charge Cations
• Some “d-block” elements are capable of forming ions with different charges
In these cases Roman numerals are used to indicate which ion / charge is used