Chem32 chapter 3.txt
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- What is a chemical bond?
- A bond between two atoms that is so strong that the atoms stay in contact with each other.
What is a covalent bond?
A bond formed between two or more atoms by those atoms sharing electrons with each other.
Only groups 4a through 7a can form covalent bonds. Though hydrogen can too.
Not all electrons in covalently bonded atoms need to be part of the bond. Non-bonded electrons can exist in pairs outside of the bonds.
What is a molecule?
A group of two or more atoms bound by covalent bonds.
What is a bonding electron pair?
The pair of electrons shared by two atoms bound by a covalent bond.
What is the "octet rule"?
Group 8a elements, noble gasses, each have 8 electrons in their outer-most/valence shell and are very stable.
When atoms form a covalent bond they share electrons in such a way that each atom has ( by sharing ) 8 valence electrons.
What is a lone pair?
A pair of electrons not used in the bonding of two atoms bound by a covalent bond.
What kinds of elements can form covalent bonds?
Only elements in groups 4a through 7a can form covalent bonds.
Groups 1a through 3a cannot form covalent bonds.
How many bonds does a particular atom need?
However many empty spaces it has in its valence shell.
Group 7a elements have 7 valence electrons and 1 empty valence space. Group 7a elements can form 1 covalent bond.
Group 5a - 5 valence electrons, 3 empty spaces - 3 covalent bonds.
What are single, double, and triple bonds?
Covalent bonds using one, two, and three pairs of electrons, respectively.
What groups of atoms can bond with themselves?
Group 5a, 6a, and 7a atoms can bond with themselves.
What is electronegativity?
An element's strength of attraction for electrons. How strongly an element attracts electrons. Higher attraction equals higher electronegativity.
What is a polar covalent bond?
A covalent bond in which one atom has a much higher electronegativity than the other and thus a stronger attraction for the shared electrons.
Since the atom with the higher electronegativity has a stronger pull on the shared electrons, the shared electrons spend more time with it and the higher-electronegativity-atom becomes negatively charged while the lower-electronegativity-atom becomes positively charged.
With one side of the bond positive and the other side negative the bond becomes polar.
What is a nonpolar covalent bond?
A covalent bond in which the two covalently bonded atoms have equal or very similar charges.
How do you name a -covalent- compound?
For the first part, if there is only one atom of the element it is simply the name of the element. If the first element is a single Na atom then the name starts with "sodium". If there is more than one atom then it starts with a prefix that tells the number of atoms. If the compound starts with 2 Na it will be "disodium". If three Na, "trisodium".
For the last element of the compound it will also have a prefix telling how many of those atoms are there ( "mon" for 1 ) but will also change the suffix of the last element's name to "ide". So, 2 Cl in the last part of a compound will be "dichloride", 3 Cl would be "trichloride". If it's just one Cl at the end of an element it will be called simply "chloride".
How do you name an anion?
When an atom gains one or more electrons and becomes negatively charged it becomes an anion. Anions are named by changing the ending of their name to "ide". When fluorine ( F ) gains an electron and becomes negatively charged it becomes a "fluorIDE anion".
What elements can become anions?
Group 1a, 2a, and 3a elements have 1, 2, and 3 valence electrons respectively. Elements in these groups can lose all of their valence electrons to become anions.
What is an ionic compound?
A compound made from ions, duh. :)
When an atom with 1 valence electron comes into contact with an atom with 7 valence electrons the atom with one v.e. loses its electron to the atom with 7 v.e.. The atom that lost a v.e. becomes positively charged while the atom that gained an electron becomes negatively charged. Since the atoms are now oppositely charged they are attracted to each other and bond to form an ionic compound.
What is an ionic bond?
The bond between two oppositely charged ions that are attracted to each other.
Two ions bound to each other by ionic bond is -not- a molecule.
Atoms bound to each other by covalent bonds are molecules. Are atoms bound by ionic bonds molecules?
No. They are ionic compounds.
What is the rule of charge ballance?
The positive charges must equal / cancel out the negative charges in an ionic compound. If one ion with a 3- charge is attatched to 3 other ions then those 3 ions must all be 1+.
- 3- on one side, 1+, 1+, 1+ on the other.
- 3+, 3+ on one side, 2-, 2-, 2- on the other.
What is the trick to knowing how many ions are in a compound?
If X ion is 3+ and Z ion is 2- then you need 3 Z ions and 2 X ions.
What's the difference between CuCl and CuCl2?
CuCl is an ionic compound made of one Cu+ and one Cl- ion. CuCl2 is an ionic compound made from one Cu(II) and two Cl- ions. The Cu(II) ion has a 2+ charge, hence the (II), so it needs two Cl ( each with 1- charge ) to satisfy the rule of charge balance.
Are ionic compounds named in the same way covalent/molecular compounds are named?
No. Covalent/molecular compounds tell how many of each atom are in the compound, names for ionic compounds do not do this.
How do you name ionic compounds?
Names of metals in ionic bonds do not change. Magnesium from the periodic table is still magnesium in the name of an ionic compound.
1. List the positively charged cation first. If it is a transitional metal that can form two different ions then the kind of ion it is must be specified. Fe2+ = iron(II), Cr3+ = chromium(III).
2. List the negatively charged anion, add "ide" to the end of its name, chlorine = chloride. Even if there is more than one chlorine atom we don't note it in the compound's name.
How do you write a formula for an ionic compound?
1. Name the positively charged cation first. If it is a transitional metal that can form more than one ion do not list which ion it is. Fe(II) or Fe(III) in this case is just Fe.
2. Add subscript to tell how many of that cation are there.
3. Name the negatively charged anion and subscript to show how many of those anions there are in the compound.
How do you know how many ions of a transitional metal that can form different ions are in a compound?
Fe2O3 has 2 Fe ( iron ) ions and 3 O ( oxygen ) anions. The formula doesn't say if it is Fe(II) or Fe(III) though. We know that O is 2- though and there are three of them, totaling a 6- charge. The two Fe cations must total a 6+ charge. Since there are two of them they must be 3+ each so, Fe(III).
What is amonatomic ion?
An ion made up of only one atom. Like when lithium (Li) or sodium (Na) loses their one valence electron they become ions and are only one atom.
What is a polyatomic ion?
An ion made up of more than one atom. If O ( 6v ) formed a covalent bond with H ( 1v ) to total 7v and then stole an electron from an atom with one v.e., like Na ( 1v ) then the OH would have 8v, satisfy octet rule, and have a 1- charge, thus being a polyatomic ion.
How do you write the formula of a compound containing a polyatomic ion?
The polyatomic ion is kind of treated as if it were an individual atom. Sulphate ( SO4) ( 2- ) would be written as SO4 if there were just one of the ions in the compound or (SO4)2 if there were 2 sulphate ions in the compound.
How do you name an ionic compound?
Pretty much the same way as naming ionic compounds. No prefixes telling how many of an ion there are. The polyatomicion is named as itself. Mg in MgSO4 is called magnesium and the SO4 is called sulphate. Magnesium sulphate.
How can you recognize an ionic compound?
If it contains a metal, it's probably ionic.
If it contains NH4 ( ammoniUM ) it is probably ionic.
How can you recognize a molecular compound?
If it contains only nonmetals, it is probably molecular.
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