scie Flashcards
These are the electrons located at the outermost (highest) principal energy level of a representative or noble gas element.
Assigning valence electrons is only applicable to representative elements, that is, groups IA to VIIIA (transition elements in the d sublevels are NOT included)
It is, therefore, common to see valence electrons in the s or p sublevels.
Valence Electrons
The electrons located between the valence electrons and the nucleus are called core electrons. In other words, all the other electrons which are not found in the outermost shell are considered core.
Core electrons
is also called Lewis Dot Diagram or Lewis symbol.
Gilbert Lewis, an American chemist, first introduced this shorthand symbol
devised by scientists to designate the valence electrons of the atoms in an element
Lewis Dot Diagram
have complete outermost electrons.
noble gases
the maximum number of valence electrons for any element
eight
This rule states that the atoms of an element lose, gain or even share electrons so that their electron configurations achieve eight valence electrons.
This will be the basis for the next topic, chemical bonds.
octet rule
A force that holds groups of two or more atoms together and makes them function as an intact unit.
chemical bond
Bonds involve the electrons in the
outer shells of atoms
The atoms of noble gases have full outer shells and so are stable.
This makes the noble gases very unreactive, and so they do not usually form bonds.
The atoms of other elements have incomplete outer electron shells making them unstable.
are formed when different elements chemically react with each other.
compounds
occurs between nonmetals atoms only
covalent bonding
occurs between metal and nonmetal atoms.
ionic bonding
occurs between metal atoms only
metallic bonding
All bonds involve electrons, and all bonding includes changes in the number of valence electrons.
metal is at the right side
non metal left side kasama yung H
For a substance or mixture to conduct electricity
It must contain charged particles.
Charged particles must be free to move or migrate.
conductivity
Ionic compounds are always electrolytes if they DISSOLVE in water
A type of chemical bond due to the attractive electrostatic force between cations (+ metal) and anions (- nonmetals)
Electrostatic forces: attraction/repulsion that exists between charged particles.
Ionic bonding
Electrolyte - conducts electricity - release ions when dissolved in water (dissociation or ionization)
Non-electrolyte- does not conduct electricity- no mobile or dissociated ions
are due to the sharing of electrons by two (or more) nonmetal atoms.
covalent bonding
form when one atom “TRANSFERS” an electron with another atom.
is the electrostatic force that holds OPPOSITE CHARGES in a compound: METAL(cation, +) and NONMETAL(anion -)
Ionic Bond
is an atom or molecule that is positively (+) or negatively (-) charged
is created when a neutral atom accepts or donates one or more electrons.
Ion
The collective set of rules that help you name chemical formulas is known as
nomenclature
CASE 1: Representative metal + nonmetal
When naming binary compounds, the following rules apply:
In the compound name, metal cations are named the same as on the periodic table, while anions change their ending to –ide.
Cations are always written first in an ionic formula, followed by the anion.
General pattern: metal name + nonmetal name (-ide)
For example, in NaCl, the Na cation keeps its name – sodium – while the anion changes from chlorine to chloride.
The crisscross method: Writing the Chemical Formula of Binary Ionic Compounds
Ionic compounds must be electrically neutral therefore, the total amount of positive and negative charge must be the same. This is the rule that determines how many of each ion species are needed in the chemical formula. The crisscross method uses ion charges to determine how many of each ion must be present in the neutral chemical formula.
CASE 2: Transition metal + nonmetals
Copper, for example, can form an ion with either a 1+ or a 2+ charge. In the table below, there are several names for monatomic cations followed by a Roman numeral. A Roman numeral specifies which charge the ion should have when naming the compound or crisscrossing to write the formula. When you see a cation with Roman numeral 3, III, the ion’s charge is 3+. When you see a cation with II, the charge is 2+, and so on.
Transition metals are the elements that belong to the d-block, and they can have multiple charges.
There are two methods in naming transition metals in a compound:
- IUPAC (International Union of Pure and Applied Chemistry) name or Modern Stock System
Some metals always form the same ion with the same charge, but many metals can form ions with different charges. Makes use of Roman numerals (indicate the ion charge)
- Traditional or Old Stock System
element root name + ous ending: refers to the ion with a lower charge.
element root name + ic ending: refers to the ion with a higher charge.
Table 1. Some transition metals and their old and modern names.
RULES:
General pattern: transition metal name (Stock/Traditional) + nonmetal name (-ide)
The metal names are always written first
The ending of the nonmetal is replaced with “-ide”
Examples:
- CuCl
First, determine the charge of Cu used in the compound. Since Cl has no subscript, it means that the charge of Cu that was used is 1+. Similar to case 1, the transition metal name is retained but the suffix of the nonmetal will be changed to -ide.
Stock name (Modern): Copper (I) chloride
Traditional name: Cuprous chloride
- FeCl3
Determine the charge of Fe used in the compound. Since Cl has a subscript of 3, it means that the charge of Fe that was used is 3+. If we look at the table, we will use Iron (III) as the modern name, and Ferric as the traditional name.
Stock name (Modern): Iron (III) chloride
Traditional name: Ferric chloride
B. The Covalent Bond
Covalent bonds form between atoms that are identical or close to each other on the periodic table, usually in non-metals. The bonds between hydrogen and oxygen atoms in H O are covalent bonds. Each covalent bond is a single shared electron pair. Covalent bonds are local - they connect two specific atoms.
Involves nonmetals
To attain stability, the electrons are shared
Sharing of 1 or more valence electrons form a chemical bond known as covalent bonds
CASE 3: Non-metals
Let’s look at binary covalent compounds. Binary covalent compounds have a simple naming procedure:
Use the same rules for naming simple binary ionic compounds.
Add a prefix to each name that indicates how many of that atom are in the molecule.
If there is only one atom of the first element in the chemical formula, leave out the “mono” prefix. This rule applies only to the first element in the formula.
is a compound made of only two atoms with a covalent bond.
Carbon monoxide, CO, is a diatomic molecule made of two different atoms. Oxygen gas, O2, is a diatomic molecule made of two of the same atoms.
Diatomic Molecules
7 elements that form diatomic molecules
There are seven elements on the periodic table that are found in nature in their pure form bonded to each other as a diatomic molecule. These seven elements are: hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. The seven are all non-metals, they exist as gases at room temperature, and they have the chemical formula X2 where X represents their element symbol: H2, N2, O2, F2, Cl2, Br2, I2. When you are told one of these elements is involved in a chemical reaction, you must assume it is in its diatomic form, not its elemental or atom form.
