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What are valence electrons?
the electrons in the highest occupied energy level of an element’s atoms
What is the number of valence electrons related to?
the group numbers in the periodic table
How do we find the number of valence electrons in a representative element?
by looking at its group number (1A = 1 val. electron)
What electrons are used in chemical bonds?
Valence electrons
What are electron dot structures?
diagrams that show valence electrons as dots
What did chemist Gilbert Lewis do? What did he call it?
He used the unreactive nature of noble gases to explain why atoms form certain kinds of ions and molecules; the octet rule
In forming compounds, atoms tend to achieve the electron configuration of a ________.
noble gas
What is an octet?
a set of 8
What is the general electron configuration of a noble gas?
ns2 np6
What is the octet rule?
Atoms of the metallic elements tend to lose their valence electrons, leaving a complete octet in the next lowest energy level. Atoms of some nonmetallic elements tend to gain electrons or to share electrons with another nonmetallic element to achieve a complete octet
When does an ion form?
when an atom or a group of atoms loses or gains electrons
What is a cation? When does it form?
a positively charged ion; when an atom loses electrons
For metallic elements, what is the name rule?
the name of the ion is the same as the name of the element
What elements provide a typical example of the formation of cations?
Sodium (Na); Magnesium (Mg)
What is the charge pattern?
Group 1A cation always have a charge of 1+; Group 2A cation always have a charge of 2+; the charges of transition metal cation may vary
Does silver achieve a noble gas configuration when it forms an ion?
no
what happens if silver loses its 5s1 electron?
the outer electron configuration that is left is 4s2 4p6 4d10; it forms a pseudo noble-gas electron configuration
What are some electrons make pseudo noble-gas configurations?
Copper (Cu); Gold (Au); Cadmium (Cd); Mercury (Hg)
What is an anion and when does it form?
an atom or a group of atoms with a negative charge; when electrons are gained by a neutral atom
What is the name rule for anions?
The ending of the element name is usually removed and replaced with -ide
How do atoms of non-metallic elements attain noble-gas configurations? What element is an example?
by gaining electrons than by losing them; chlorine
What can we use electron dot structures to make?
to write an equation showing the formation of an ion from a certain element
What are halide ions?
the anions formed by halogen elements
All halides ______ valence electron and attain a charge of _____
gain one; 1-
How does oxygen attain the electron configuration of neon?
by gaining 2 electrons
What are monatomic ions?
ions that consist of a single atom with a positive or negative charge
What groups in the periodic table have positive charges?
Groups 1,2, and 13
When naming cations, what should the name end with?
ion or cation
How can we find the charge of any ion of a representative nonmetal?
by subtracting 18 from the group number
what are ionic compounds?
Compounds composed of cations and anions
What are ionic compounds often formed from?
metal cations and nonmetal anions
What charge do ionic compounds have?
a neutral charge
How do anions and cation attract each other?
by means of electrostatic forces and by having opposite charges
What are ionic bonds?
The electrostatic forces that hold ions together in ionic compounds
How do chemists represent the composition of substances?
by writing chemical formulas
What does a chemical formula do?
it shows the kinds and numbers of atoms in the smallest representative unit of a substance
One example of a chemical formula:
NaCl
What does an ionic compound’s chemical formula refer to and why?
a ratio known as a formula unit; because ionic compounds are made up of positively and negatively charged ions arranged in repeating patterns
What ais a formula unit?
the lowest whole number ratio of ions in an ionic compound
What does the 2 in MgCl2 represent?
The ratio of the magnesium cations to the chloride anions - 1:2 (one Mg2+ to two Cl-)
Most ionic compounds are _________ at room temperature
crystalline solids
How are the component ions of crystals arranged?
in repeating, three dimensional patterns
What are the melting points of ionic compounds like?
The melting points of ionic compounds are high
What has to be done in order to break an ionic bond?
the bonds between the ions must be broken so that ions may freely flow past one another
Why was the Powerade able to conduct electricity?
because its ions were able to move freely throughout the material
What is the coordination number of an ion?
the number of ions of an opposite charge that surround the ion in a crystal
When can ionic compounds conduct an electric current?
when melted or dissolved in water
In order for an electric current to pass through a material, charged matter _________ through the material
must be able to move
why can’t ionic solids conduct electricity in the solid state?
because their ions are locked into place and cannot move
What happens when an ionic solid is melted or dissolved?
the crystal structure breaks down, and the ions are free to move
What happens when voltage is applied to the molten mass or solution?
cations freely move to the negative electrode, and anions flow freely to the positive electrode (creates an electrical current)
What happens to ionic solids when met with a large force?
they crack (not shatter) because the ions become misaligned (negative w/ negative) (positive w/ positive) causing them to repel each other
What are monatomic ions?
ions that consist of a single atom with a positive or negative charge
What periodic table groups make cations?
Groups 1,2, and 13
How do we find the charge of an ion of representative elements?
by subtracting 18 from the group number
What do the names of anions end with?
-ide
How are the charges of transition metal ions found?
by determining the number of electrons lost
What is the stock system?
a system in which a roman numeral is placed in parentheses indicating the numerical value of the charge
What is the name for Fe2+
Iron (II) ion
What can many transition metal compounds be used as?
pigments
What are polyatomic ions?
ions composed of more than one atom
What do the names of most polyatomic anions end in?
-ite or -ate
What is a common name for potassium carbonate?
Potash
Who developed a method to name chemical compounds?
Lavoiser
What is a binary compound?
A compound composed of two elements and can be either ionic or molecular
How do we name any binary ionic compound?
first place the cation name first, followed by the anion name
How do we write the formulas for binary ionic compounds?
Write the symbol of the cation and then the anion. Add whatever subscripts are needed to balance the charges.
What do the charges of binary ionic compounds have to equate to?
zero
How would you write the formula for an ionic compound with a polyatomic ion?
Write the symbol for the cation followed by the formula for the polyatomic ion and balance the charges
When do we use parenthesis in a chemical formula?
when the compound contains more than one polyatomic ion
How do you name a compound containing a polyatomic ion?
state the cation first and then the anion just as you did in naming binary ionic compounds
What are binary molecular compounds composed of?
two elements, but both elements are nonmetals and they are not ions
Do we need to balance the charges in binary molecular compounds?
no because binary molecular compounds are composed of molecules, not ions, so ionic charges cannot be used to write formulas or to name them
What do the prefix in the name of a binary molecular compound tell us?
how many atoms of each element are present in each molecule of the compound
Prefix for one
mono-
Prefix for two
di-
Prefix for three
tri-
Prefix for four
tetra
Prefix for five
penta-
Prefix for six
hexa-
Prefix for seven
hepta-
Prefix for eight
octa-
Prefix for nine
nona-
Prefix for ten
deca-
What do the names of all binary molecular compounds end in?
-ide
Guidelines for naming binary molecular compounds
First, confirm that the compound is a binary molecular compound composed of two - that is, a compound nonmetals
The name must identify the elements in the molecule and indicate the number of each atom of each element
Name the elements in the order listed in the formula
Use prefixes to indicate the number of each kind of atom.
How do we write the formula of a molecular compound given its name?
Use the prefixes in the name to tell you the subscript of each element in the formula. Then write the correct symbols for the two elements with the appropriate subscripts
