bonding Flashcards
What is a chemical bond?
A force that holds atoms together
Why do atoms form chemical bonds?
To become stable by reaching a full outer shell, usually of 2 or 8 electrons
What is the octet rule?
Elements combine to fill their outermost shell. For a lot of elements, this means 8 electrons in the outermost shell.
How is # of valence electrons determined for elements in Periods 1,2, or 13-18?
Look at them as being their own thing and ignore the transition metals and Lanthanides and Actinides. Then, they have the # of valence electrons relating to their period number Period 1=1 valence Period 2=2 valence Period 13=3 valence Period 14=4 valence
Transition metals usually have ___ or ____ valence electrons, but some can have up to ____ or _____
2
3
5
6
Which period has the most stable atoms?
Period 18
What is an ionic bond? What kind of elements does it happen between?
A bond where one atom “gives away” an electron to another atom and a new bond is formed by the attraction between the ions
nonmetal and metal
What is a covalent bond? What kind of element does it happen between?
Two atoms share electrons to reach their full outer state
nonmetals
What is a metallic bond? What kind of element does it happen between?
atoms connected through a “sea of electrons”
metals
What causes ionic bonds?
Electrostatic Attraction, or when two oppositely charged objects are attracted to each other (in this case, ions)
What is a simple ion?
An ion formed from a single ion (ex: H+)
What is a polyatomic ion?
An ion that is formed when two or more atoms join together (so in other words, a bunch of atoms that are ionically bonded makes up a polyatomic ion).
(ex: Ammonium with one atom nitrogen and 4 hydrogen atoms, or hydroxide with one atom oxygen and one atom hydrogen)
Talk out loud and explain how calcium and oxygen bond to make CaO
Calcium wants to get rid of 2 electrons (is a metal, wants to get to a full outer shell)
Oxygen wants 2 electrons (is a nonmetal, wants to get a full outer shell)
Calcium gives electrons to Oxygen and then they become attracted to one another as Calcium gains a 2+ attraction and Oxygen gains a 2- attraction
2- and 2+ cancel out, so the two make CaO
Talk out loud and explain how sodium, oxygen, and hydrogen bond to make NaOH
Oxygen and Hydrogen bond to make OH as Hydrogen only needs one more electron
Then Oxygen still needs one more electron even though it’s bonded with hydrogen, and Sodium has 1 extra electron that it can give oxygen.
So Sodium bonds with oxygen, which is already bonded to hydrogen, so altogether they make NaOH
An ionic compound always has a net charge of ____. Why?
0
Because the positive charge of the cations will be equal to the negative charge of the anions.
What are some properties of ionic compounds? (4)
- bond is hard to break (electrostatic attraction is strong)
- high melting point and high boiling point (opposite of covalent bond)
- hard and brittle
- salts (just means they are made from a nonmetal and metal) (exceptions are oxides which have a metal and an oxygen and hydroxides which have a metal and a hydrogen)
How are ionic compounds arranged? How are the anions arranged? How are the cations arranged?
In a crystal lattice.
The anions line up in a sort of cubical shape with anions on the inside too.
Because nonmetal anions are bigger than metal cations, as the anions line up, the cations fit into the spaces within the anions
(look up a picture if confused)
Can ionic bonds have more than one element?
Yes
How do magnesium and chlorine form an ionic bond?
Chlorine needs one electron but magnesium needs to get rid of two. Hence, 2 chlorine atoms are needed to fulfill the requirements of one magnesium atom and together they form MgCl2
What happens to ionic compounds in water?
They disassociate (break up into ions) Once cations and anions are free to float around, they can conduct electricity
Covalent bonding occurs mostly between nonmetals that are _____
close to each other on the periodic table (similar electronegativities)
What are some properties of covalent compounds?
- low melting and boiling points (opposite of ionic bond)
- don’t conduct electricity
- don’t dissolve well in water
- more flammable than ionic compounds
- not as hard as ionic compounds
What is a diatomic molecule?
A molecule where an atom has formed a covalent bond with itself to become more stable (ex: H2, O2)
What is a double bond?
Appears when two atoms share 4 electrons
What is a triple bond?
Appears when 3 atoms share 6 electrons
What is the duet rule?
For Helium and hydrogen, a full outer shell is 2 electrons.
How do some group 3 elements bond?
Settle for a covalent bond 3 valence electrons (ex: BH3 or Boron and 3 Hydrogen)
