chapter 7 ionic and covalent bonds. review chemical bonds form between 2 or more atoms to form...
TRANSCRIPT
Review
Chemical Bonds form between 2 or more atoms to form molecules
Two types of chemical bonds:
Ionic Bonds & Covalent Bonds
Ionic Bonds & Covalent Bonds
Ionic Bonds- Electrons are transferred between a metal and a non-metal
Covalent Bonds- Electrons are shared between two non-metals
Remember: The “stairs” on your periodic table separate the metals and non-metals
In this Chapter…You will understand HOW and WHY Ionic and Covalent Bonds form
To start- remember that an element becomes stable with 8 Valence ElectronsHydrogen and Helium are exceptions, they only need 2 to be full
Atoms will give, take, or share electrons to get to 8 Valence Electrons
ElectronegativityWhen two atoms have a big difference in electronegativity the electron gets transferred
When there is a small difference the atoms share the electron
This is WHY the atoms form the type of bonds that they do
Ionic BondsForm between a metal and a non-metal
There’s usually a big difference in electronegativity, which causes the metal to give its electrons to the non-metal
Example: K and O (3.5 - .8 = 2.7 difference)
They transfer enough electrons so that both the metal and non-metal have 8 Valence Electrons
IonsWhen atoms give or take electrons they become charged Ions
Metals lose electrons to become cations (+)Non-metals gain electrons to become anions(-)
Opposite charges attract, ions come together to form neutral molecules
Ion FormationTo figure out what ion an element will form:
If it is a metal: Find out the number of valence electrons it needs to LOSE to get to zero.Many Transition Metals can form more than 1 Ion
If it is a non-metal: Find out the number of valence electrons it needs to GAIN to get to 8
Hydrogen can both lose and gain 1 electron
Simple Ion Nomenclature (naming)
Simple cations are named by saying the element and adding the word “ion.”Na+ is called “sodium ion”Mg2+ is called “magnesium ion”
Simple anions are named by dropping the ending off the element name and adding “ide.”F- is called “fluoride”O2- is called “oxide”N3- is called “nitride”
Element Symbol Name Formula
1Sodium Na Sodium Ion Na+
2Bromine Br Bromide Br-
3Magnesium Mg Magnesium Ion Mg2+
4Chlorine Cl Chloride Cl-
5Oxygen O Oxide O2-
6Boron B Boron Ion B3+
7Lithium Li Lithium ion Li+
8Neon Ne Neon Ne
9Phosphorus P Phosphide P3-
10Aluminum Al Aluminum ion Al3+
11Calcium Ca Calcium Ion Ca2+
12Iodine I Iodide I-
13Nitrogen N Nitride N3-
14Cesium Cs Cesium ion Cs+
15Sulfur S Sulfide S2-
16Fluorine F Fluoride F-
17Potassium K Potassium Ion K+
18Barium Ba Barium ion Ba2+
19Hydrogen H Hydride AND Hydrogen ion H+ AND H-
20Helium He Helium He
Ions ShortcutPull out your periodic tables!
Group 1 = 1+
Group 2 = 2+
Group 13 = 3+
Group 14 = 4+ or 4- ***Depends on what it bonds with
Group 15 = 3-
Group 16 = 2-
Group 17 = 1-
Simple Ionic Compounds
Ions come together to form neutral compounds
Today we will learn how to: Write the chemical formula of the compound created
Figure out the name for the compound
Chemical Formulas of Ionic Compounds
With the criss-cross method you use the charge of the cation to figure out the subscript of the anion and vice versa
We write chemical formulas of ionic compounds using the criss-cross method
Criss - Cross Method
When possible, reduce the subscripts to get the most simple version of the chemical formula
Situation 1: Ions with the same charge
Mg2+ and O2- would be written as MgO, NOT Mg2O2
Situation 2: Any subscript with a 1
Mg2+ and Cl- would be written as MgCl2 NOT Mg1Cl2
Naming Ionic Compounds
When naming ionic compounds, simply write the element name of the metal followed by the ion name of the nonmetal.
The metal ion (cation) is always written firstThe name of the metal is capitalized while the ion of the non-metal is not
NaCl is called “Sodium chloride” CaCl2 is called “Calcium chloride”
TodayMini-quiz: How to find IonsReview how to write formulas for Ionic CompoundsDiscuss how to name Ionic CompoundsWHY Ionic Bonds form the compounds they doHW: Ionic Bonding WS
Mini-Quiz: Take out a half sheet of paper and your periodic table
What Ions do the following elements form?
S Li Al Ne Br
Naming Ionic CompoundsUse the “Criss-Cross” Method to write ionic compounds: If the charges have the same number, you do NOT write the subscriptIf the number is a 1, you do NOT write the subscript
Practice- Take out your worksheet from yesterday
1. Na and Br: Na+ and Br- so NaBr
2. Ca and Cl Ca2+ and Cl- so CaCl2
3. Mg and S Mg2+ and S2- so MgS
Try #4 Al and O and #5 Li and P
Naming Ionic CompoundsWhen naming ionic compounds, write the element name of the metal followed by the ion name of the nonmetal.
NaCl is called “Sodium chloride” CaCl2 is called “Calcium chloride”
Polyatomic IonsA polyatomic ion is made up of 2 or more atoms that are covalently bonded, but have an overall charge
Even though they are multiple atoms, we treat it like 1 ion
A list of polyatomic ions with their charges is given on your reference sheet– you need to keep this safe!
Polyatomic Ions in Formulas
Still use the same criss-cross methodSince the subscript applies to the ENTIRE polyatomic ion, the ion goes in ( ) with the subscript on the outside
Example: Mg and OH
Mg2+ and OH- form Mg(OH)2
Naming polyatomic ionsLook up the name of the polyatomic ion using the polyatomic reference sheet
The regular ion uses the same naming as usual Full name for Cation (+) -ide ending for Anion (-)
Examples: Mg and OH Magnesium Hydroxide
Na and MnO4 Sodium Permanganate
Transition MetalsEven though transition metals technically have 2 valence electrons, they don’t act like it
Transition Metals can form a wide variety of cations
We will use our reference sheet to see what ions the various transition metals can form
Figuring out transition metal charge
If the ion that goes with the metal does NOT have a subscript, then the metal has the same charge as the other ion
AuCl = Au+ because Cl- FeO = Fe2+ because O-2
If the ion that goes with the metal DOES have a subscript, then the metal has the ion charge of the subscript
AuCl3 = Au3+ Fe2O3 = Fe3+
Practice
What is the charge on Zn in ZnCl2?
What is the charge on Cr in CrO?
What is the charge on Co in CoBr3?
What is the charge on Ni in NiSO4?
Figuring out ion charge without the formula
Without the formula given, you cannot know which ion charge to use (when there is more than one choice)
When the formula is not given, you must write the formula for all possible ion choices
Example: What is the formula for Cu and Cl?
CuCl and CuCl2 are both the correct answer, you need both!
Naming Transition MetalsTwo types of names- standard and common name
Standard name: Regular metal name with the ion number in roman numerals in parenthesis
Example: Fe2+ Iron (II)
Common name: Based on Latin Names
Example: Fe2+ Ferrous
Both are found on your transition metals reference sheet!