a substance whose smallest particles include more than one element chemically bonded together
100
What did we use to represent covalent bonds when we made molecules out of clay?
toothpicks
100
What does the 2 in H20 stand for?
The subscript 2 tells us that there are two hydrogen atoms in the molecule.
100
What are electrons in the outermost energy level of an atom called?
Valence electrons
100
What is an ion?
An ion is a charged atom that occurs when the atom either gains or loses an electron.
200
Describe a mixture
a substance that contains two or more elements and/or compounds that are not chemically bonded together
200
Covalent is one type of this kind of bond
a chemical bond
200
What does it mean when there is no number (in subscript) next to an element symbol in a chemical formula?
There is only one atom of that element present in the compound.
200
What is the "magic number" for chemical bonding?
eight
200
Describe what happens in the formation of an ionic bond.
One atom steals an electron from another and the oppositely charged atoms are attracted and move close to one another.
300
What makes an element different than a compound?
An element cannot be separated into a simpler substance by physical or chemical means
300
What is the main characteristic of a covalent bond?
In covalent bonds the atoms share their electrons.
300
When we make a diagram on paper, it is difficult to show this important structural feature of a molecule
the three-dimensional shape
300
Why is eight the magic number for chemical bonding?
Atoms try to fill their outermost energy level, which for most common elements hods eight electrons.
300
Give the chemical formula, compound name and common name of an ionically bonded compound that you come in contact with every day. (Hint: we have used this in more than one experiment in the last month.)
NaCl - Sodium Chloride - table salt
400
Table sugar is an example of this kind of substance
a compound
400
Give three examples of molecules formed by covalent bonds
What do the dots in a Lewis dot diagram represent?
The dots in a Lewis dot diagram represent the valence electrons of the element(s).
400
Why are electrons from one atom attracted to other atoms?
They are attracted by the positive charge of other atoms' nuclei.
400
What is the sum of the oxidation numbers for all atoms in a compound?
Zero.
500
Rocks are examples of this kind of substance
a mixture
500
What are two conditions atoms must have in order to form covalent bonds with one another?
There is a strong enough attraction between atoms and there is room for electrons in the outer energy level of both atoms.
500
How many dots are around each element symbol in a Lewis dot diagram of a complete molecule?
There will be either 2 or 8 dots around each element symbol in a Lewis dot diagram.
500
How can you tell how many valence electrons an element has?
Its position on the periodic table can indicate the number of valence electrons, or you can draw a diagram -- filling in energy levels with the maximum electrons until you get to the outermost level.
500
What does the oxidation number of an atom tell us?
The oxidation number indicates the charge of an atom, and can help us predict what other atoms might bond with it.