CHEMICAL BONDS AND COMPOUNDS Flashcards
Four periodic table sections
- Representative Elements
- Noble - gas Elements
- Transition Elements
- Inner Transition Elements
Compounds are divided into two broad categories:
Ionic compounds
Molecular compounds (Covalent)
Note: Certain combinations of elements produces ionic compounds, some other combinations form molecular compounds
the attractive force that holds two atoms together in a more complex unit
Chemical bond
note: It is important to note that most bonds are not 100% ionic or 10% covalent
Two types of chemical bond
Ionic bonds
Covalent bonds
formed through transfer of one or more electrons from one atom or group of atoms to another
Ionic bonds
formed through the sharing of one or more pairs of electrons between two atoms
Covalent bonds
There are two fundamental concepts to understanding ionic and covalent bonding models
- Not all electrons in an atom participate in bonding. Those that do are called valence electrons
- Certain arrangements of electrons are more stable than others, as is explained by the octet rule
an electron in the outer-most electron shell of a representative or noble-gas element
Valence electron
The number of valence electrons in an atom of a representative element can be determined from the atom’s what
electron configuration
the chemical symbol of an element surrounded by dots equal in number to the number of valence electrons present in atoms of the element
Lewis symbol
The General Practice in writing lewis symbol
The general practice in writing these symbols is to place the first four dots separately on the four sides of the chemical symbol and then begin pairing the dots are further dots are added
Lewis Symbol: Three things to note:
- Representative elements in the same group of the periodic table have the same number valence electrons
- The number of valence electrons for the representative elements is the same as the Roman numeral periodic-table group number
- The maximum number of valence electrons for any element is eight
produced as a result of ionic bonding
Ions
an atom (or group of atoms) that is electrically charged as a result of the loss or gain of electrons
An ion
If an atom gains one or more electrons, it becomes
a negatively charged
if an atom loses one or more electrons, it becomes
a positively charged
Loss of one, two, or three electrons gives ions
with +1, +2, or +3 charges, respectively
Gain of one, two, or three electrons gives ions
with -1, -2, or -3 charges, respectively
This kind of atom is containing one, two, or three valence electrons
(Groups IA, IIA, and IIIA) tend to lose electrons to acquire a noble gas electron configuration
Metal Atoms
Group IA metals form how many ions
1+ ions
Group IIA metals form how many ions
2+ ions
Group IIIA metals form how many ions
3+ ions
This kind of atom is containing five, six, or seven electrons
(Groups VA, VIA, and VIIA) tend to gain electrons to acquire a noble gas electron configuration
Non-metal atoms
Group VIIA nonmetals form how many atoms
1- atoms
Group VIA nonmetals form how many atoms
2- ions
Group VA nonmetals form how many ions
3- ions
Elements in this group would have to gain or lose four electrons to attain stability, but in most cases the bonding that results is more adequately described by the covalent bond model
Group IVA
Ion formation requires the presence of two elements:
a metal that can donate electrons and a nonmetal that can accept electrons
The positive and negative ions simultaneously formed from such electron transfer attract one another, forming an
ionic compound
a combination of Lewis symbols that represents either the transfer or sharing of electrons in chemical bonds
Lewis structure
Ionic compounds are always
NEUTRAL
note: The ratio in which positive and negative ions combine is the ratio that achieves charge neutrality for the resulting compound
Formula Writing Rules for Ionic Compounds
- The symbol for the positive ions is always written first
- the charges on the ions that are present are not shown in the formula
- The numbers in the formula (subscripts) give the combining ratio for the ions
In the solid state, this compound consists of positive and negative ions in such a way that each ion is surrounded by nearest neighbors of the opposite charge
Ionic Compound
Ionic compounds do not have ______molecules, only an alternating array of positive and negative ions
discreet
represent the simplest combining ratio for the ions present
chemical formulas
the smallest whole-number repeating ratio of ions present in an ionic compound that results in charge neutrality
formula unit
The compounds NaCl, CO2, P4O10 are all what kind of compounds
binary compounds
an ionic compound in which one element present is a metal and the other element present is a nonmetal
binary ionic compound
Recognizing and Naming Binary Ionic Compounds: NAMING RULE:
the full name of the metallic element is given first, followed by a separate word containing the stem of the nonmetallic element and the suffix –ide.
Ex. NaF - sodium fluoride
Name the ff. binary ionic compounds:
A.) MgO
B. Al2S3
C. K3N
D. CaCl2
Answers:
a.) magnesium oxide
b.) aluminum sulfide
c.) potassium nitride
d.) calcium chloride
Naming Binary Compounds: metals and nonmetals
- So far, it has been assumed that the only behavior allowable for an element is that predicted by the octet rule
- It is a good assumption for nonmetals and for most representative element metals
- However, there are other metals that exhibit a less predictable behavior because they are able to form more than one type of ion.
- For example, iron forms both Fe2+ and Fe3+ ions, depending on the chemical circumstances
- When naming compounds that contain metals with variable ionic charges, the charge on the metal ion must be incorporated into the name. This is accomplished using Roman numerals
Naming Binary Compounds: The chlorides of Fe2+ and Fe3+ (FeCl2 and FeCl3, respectively) are named
iron(II) chloride and iron(III) chloride
Naming Binary Compounds: CuO is named
copper(II) oxide
Naming Binary Compounds note
- If you are uncertain about the charge on the metal ion in an ionic compound, use the charge on the nonmetal ion (which does not vary) to calculate it
- For example in CuO, you can note that the oxide ion carries a -2 charge (because oxygen is in group VIA), this means that the copper ion must have a +2 charge to counterbalance the -2 charge
Naming Binary Compounds: how to calculate the metal ion charge
For example: AuCl
- To calculate the metal ion charge, use the fact that the total ionic charge (both + and -) must add to zero
(gold charge) + (chlorine charge) = 0
- The chlorine has a -1 charge (group VIIA), therefore
(gold charge) + (-1) = 0 - Thus, Gold charge = +1
- The name of the compound is gold(I) chloride
Name the ff. binary ionic compound, each of which contains a metal whose ionic charge can vary:
A. Fe2O3
B. PbO2
C. Cu2S
Answers:
A. Iron(III) oxide
B. Lead(IV) oxide
C. Copper(I) sulfide
Naming Binary Compounds: Fixed Charge
- You must know which metals exhibit variable ionic charge and which have a fixed ionic charge.
- The fixed charge metals are those in group IA (+1 ionic charge), those in group IIA (+2 ionic charge) and five others (Al3+, Ga3+, Zn2+, Cd2+, and Ag+)
- Metals from the diagram form ionic compounds without roman numerals in their names
an ion formed from a single atom through loss or gain of electrons (Cl-, Na+, Ca2+)
Monoatomic ion
an ion formed from a group of atoms (held together by covalent bonds) through loss or gain of electrons (SO42-)
Polyatomic ion
This ion contains four O atoms and one S atom, and the whole group of five atoms has acquired a charge of -2
Polyatomic Ion
form between atoms of dissimilar elements (metal + nonmetal)
Ionic bonds
occurs between similar or even identical atoms (often two nonmetals are involved)
Covalent bond
